Table of Contents
What is Analytical Balance?
- An analytical balance is a highly accurate laboratory balance used to precisely determine the mass of objects, including solids, liquids, granular substances, and powders. It is also referred to as a laboratory balance and falls into the class II balance category.
- The distinguishing feature of an analytical balance is its exceptional sensitivity, allowing for precise measurements with a readability of up to 0.00001 grams (0.01 mg). This level of accuracy makes it a valuable tool in laboratory settings. The balance can detect the weight of objects ranging from 100g and provide measurements within a margin of error of ± 0.01 mg.
- The weighing capacity of analytical balances typically ranges from 100 to 500 grams, and their readability ranges from 0.1 mg to 0.001 mg. These balances are designed to provide measurements in the sub-milligram range, enabling scientists and researchers to perform highly precise experiments and analyses.
- To maintain the accuracy of measurements, analytical balances are equipped with a draught shield or weighing chamber. This transparent cage-like enclosure serves to prevent air currents and dust from interfering with the balance’s operation. It ensures that external factors do not impact the measurement process.
- Due to their high sensitivity and accuracy, the use of analytical balances should be limited to trained individuals who are familiar with proper handling and calibration procedures. Inexperienced or untrained personnel may introduce errors or mishandle the delicate equipment, compromising the accuracy of measurements.
- It is worth noting that the readability of an analytical balance distinguishes it from a precision balance. Analytical balances have a higher readability of 0.0001 grams (0.1 mg), while precision balances typically offer a readability of 0.001 grams (1 mg). Consequently, analytical balances are more expensive due to their superior precision.
- The term “balance” itself derives from the Greek word “bilanx,” which means “two-pans.” Balances have been used since ancient times, with the earliest known examples dating back to 5,000 B.C. Two-pan balances were commonly used in laboratories until the invention of the single-pan balance in the 1950s, which revolutionized weighing practices. Nowadays, electronic balances are widely employed in laboratory settings, offering greater convenience and accuracy.
- In the context of weighing, it is important to distinguish between weight and mass. Weight refers to the force exerted by gravity on an object, while mass represents the amount of matter contained within an object. The weight of an object can vary at different locations due to differences in gravitational pull, whereas the mass remains constant.
- When measuring the mass of an object, it is typically expressed in grams. However, the terms “weight” and “weighing” are often used colloquially. Both two-pan and single-pan balances utilize a reference mass or substitute weight to determine the unknown mass of an object. Electronic balances also rely on reference weights for calibration purposes before conducting precise measurements.
- Reference weights used in balancing instruments are usually made of brass or bronze, plated with chromium or lacquer, and exceed one gram in weight. They are available in various denominations, ranging from one gram to one hundred grams. For fractional reference weights, materials like aluminum or platinum are employed, and their weights range from 500 mg to 5 mg.
- Overall, an analytical balance is a highly sensitive and precise laboratory instrument that plays a crucial role in conducting accurate measurements and experiments in scientific research and analysis. Its ability to provide measurements in the sub-milligram range makes it an invaluable tool for various fields, including chemistry, biology, pharmaceuticals, and more.
Principle of Analytical Balance – Weighing balance principle
- The principle behind the operation of an analytical balance is known as “magnetic force restoration.” These balances utilize an electromagnet to measure the mass of an object indirectly. Instead of directly measuring the mass, they determine the force required to balance the sample and then use that force to calculate the mass.
- To achieve this, an analytical balance employs an electromagnet that generates a force to balance the mass of the sample placed on the measuring pan. By adjusting the strength of the electromagnet, the balance can accurately counteract the gravitational force exerted on the sample.
- The balance is equipped with a transparent enclosure or draft shield that surrounds the measuring pan. This enclosure has doors and serves the purpose of blocking external influences, such as dust and air currents, that could interfere with the weighing process. By maintaining a controlled environment within the enclosure, the accuracy and performance of the balance are preserved.
- When an object is placed on the measuring pan, the electromagnet generates a force to balance its mass. This force acts in the downward direction to counteract the gravitational force. The balance measures this force using an electromagnetic motor, which is sensitive to changes in the electrical current passing through it.
- The electrical current required to generate the necessary force is directly proportional to the weight of the object. By measuring this current, the balance can determine the mass of the object. The mass is then displayed on the screen of the balance, allowing the user to read the precise measurement.
- In some analytical balances, a “null detector” is incorporated. This detector uses a light source to indicate when the weight of the object is equal to the electromagnetic forces applied. When the weight is perfectly balanced, the null detector signals that the measurement is accurate.
- By employing the magnetic force restoration principle, analytical balances are able to provide highly precise and reliable measurements in the sub-milligram range. The electromagnet and the electromagnetic motor work together to counteract the gravitational force and determine the mass of the object being weighed, ensuring accurate and consistent results in laboratory settings.
Types of analytical balance
- The two-pan or equal arm analytical balance, also known as a two-pan balance, was introduced by Joseph Black, a Scottish chemist. This balance operates on the principle of a first-class lever. It consists of a fulcrum, which serves as a beam over a centered pivot joint, with two pans attached to it. The pans and the central beam are supported by three prism-formed knife edges.
- In a two-pan balance, the two pans are balanced against each other. The object to be weighed is placed on one pan, while a known weight is placed on the other pan. The balance is designed to achieve equilibrium when the two pans are at the same level.
- However, there are two sources of error that can affect the accuracy of measurements with a two-pan balance. Firstly, it is crucial for the two arms of the balance to be equidistant from the center. Achieving this precise balance can be tedious, time-consuming, and challenging in practice. Even a slight difference in arm length, as small as 10-5, can result in an error of 10-5 of the weight being measured.
- Secondly, as the weight being measured increases, the beam of the balance may flex slightly over the knife edges. This flexing can cause minuscule measurement inaccuracies, affecting the reliability of the results obtained.
- Despite these potential sources of error, the two-pan or equal arm analytical balance remains a widely used instrument in analytical laboratories for its simplicity and effectiveness in weighing samples. Calibration and proper handling techniques can help mitigate these errors and ensure accurate measurements.
- The single pan or unequal arm mechanical balance is an alternative to the two pan balance that overcomes its limitations. This type of balance was introduced by Erhard Mettler in 1946 and is also known as an unequal arm mechanical balance.
- Unlike the two pan balance, the single pan balance features two knife edges with unequal balance arms. The shorter arm is designed to support the balance pan and a full complement of weights, while the longer arm contains a constant counterweight built into the balance beam.
- The operation of the single pan balance involves placing the empty pan on the shorter arm and loading the object to be weighed onto the pan. To achieve equilibrium, weights are then removed from the shorter arm to compensate for the weight of the loaded object. This method of weighing is commonly referred to as weighing by substitution.
- The single pan or unequal arm mechanical balance offers several advantages over the two pan balance. It is faster and more convenient to use since the weighing process involves only a single pan and the adjustment of weights on the shorter arm. The inclusion of a fixed counterweight on the longer arm helps to balance the load on the pan, simplifying the weighing procedure.
- This type of balance utilizes a beam with two knife edges, one supporting the weighing pan and the other acting as a pivot. The unequal arm design allows for accurate measurements by compensating for the weight of the object being weighed.
- The single pan or unequal arm mechanical balance has found wide application in various settings, including laboratories and industrial environments, where precise measurements are required. With its efficient and straightforward operation, this balance provides a reliable solution for weighing objects and substances with ease.
3. Electronic single pan balance
- The electronic single pan balance, also referred to as the electromagnetic force balance, has become a popular replacement for mechanical or single pan balances. Unlike traditional balances that rely on physical mechanisms, this type of balance utilizes the principles of electromagnetism to determine the mass of an object.
- In an electronic single pan balance, a current is passed through a coil, generating a magnetic force. This magnetic force acts as a counterbalance to the load placed on the balance pan. The strength of the magnetic force is directly proportional to the mass of the object on the pan.
- The balance operates on the simple concept that the current required to balance the load is directly related to the mass of the object being weighed. By measuring the current necessary to achieve equilibrium, the balance can provide a direct reading of the applied mass.
- This electronic balance offers the advantage of providing an immediate and accurate measurement of the mass without the need for additional comparisons or calculations. Unlike mechanical or single pan balances, which rely on comparing forces or weights, the electronic single pan balance eliminates the complexity of such comparisons.
- The electronic single pan balance has found widespread use in various fields, including laboratories, research facilities, and industrial applications. Its electronic nature allows for precise and efficient weighing, with the added benefit of digital readouts and advanced features such as tare functions and data recording.
- Overall, the electronic single pan balance offers a convenient and reliable solution for measuring the mass of objects by utilizing electromagnetic forces. Its direct reading capability simplifies the weighing process and enhances efficiency in various settings where accurate measurements are crucial.
- A microbalance is an analytical instrument designed to measure samples with an extremely high level of precision. It is capable of measuring samples to a resolution of at least 1 million parts per gram, making it suitable for accurately quantifying very small amounts of substances.
- Microbalances are used in various scientific and laboratory applications where the precise measurement of minute quantities is necessary. These balances are particularly valuable in fields such as pharmaceutical research, nanotechnology, and environmental analysis, where even the tiniest changes in mass can have significant implications.
- A typical microbalance operates on the same principle as other analytical balances, using a pan or platform to hold the sample and measuring the force required to counterbalance the mass of the sample. However, the sensitivity and precision of microbalances far surpass those of standard analytical balances.
- One specific type of microbalance is the quartz crystal microbalance (QCM). It is a highly sensitive form of microbalance that can determine the mass of extremely small objects, including viruses and nanoparticles. A QCM operates by measuring the change in frequency of a quartz crystal due to the mass deposited on its surface. The frequency change is directly proportional to the mass, allowing for highly accurate measurements of minute quantities.
- Microbalances, including QCMs, are essential tools in many scientific disciplines. They enable researchers to explore and understand the behavior of materials at the micro and nano scales, contributing to advancements in various fields, such as drug development, material science, and biological research.
- In summary, a microbalance is an analytical instrument capable of measuring samples with an exceptional level of precision. It allows for the accurate measurement of extremely small amounts of substances and is commonly used in scientific research and laboratory settings. The quartz crystal microbalance is a particularly sensitive type of microbalance that can measure the mass of tiny objects, including viruses and nanoparticles.
Parts of Analytical Balance with Functions
- Balance plate (pan): The sample of material to be measured in mass is put in the balance plate, which is a pan. Use a special cleaning brush or a clean microfiber cloth to clean this area.
Weighing Sensor: Resistance strain sensors and electromagnetic force sensors are the two main types of weight sensors used in analytical and precision balances right now.
- Resistance strain sensors: Precision balances and analytical balances with only some precision often have resistance strain sensors. The way it works is that when an outside force acts on the strain gauge that is stuck to the surface of the sensor’s elastic body, the elastic body deforms and the resistance value changes. In order to get the weight value, the Stone Bridge changes the resistance signal into a voltage signal. Resistance strain sensors have a simple design, are less expensive, and are very stable. But the downside is that there is a strict limit on how much the sample can weigh. If the sample weighs more than the upper limit of the scale’s range, the sensor could be damaged.
- Electromagnetic force sensors: Analytical scales often have electromagnetic force sensors. The basic idea is that when gravity pulls on the weighing pan, the lever under the pan moves the coil connected to it in the magnetic field. The coil is then powered to cut the magnetic field, which creates electromagnetic force, which is then turned into a weight value by converting the current. The electromagnetic force sensor has a wide range of accuracy that can measure up to 10-8 g.
- Weights: helps to make sure that analytical scales are accurate. So that the calibration of the balance stays accurate, the materials that make up the weights are made with exact weights.
- Water pass: A tool that is used to figure out where the balance plate is. The balance plate can also be moved with the help of Waterpass.
- Power button (on / off button): used to turn on or off the balance. After pressing the power button to turn on the scale, it is usually left alone for 10 to 15 minutes before it is used to get a more accurate reading.
- ‘Re-zero’ or ‘Tare’ button: used to get the balance back to a neutral point (zero). We suggest that you don’t use this button too often so that the scale can still measure things correctly.
- ‘Mode’ button: used to set the system that is used to measure. You can change the conversion system by pressing the “Mode” button.
- Level indicator- It makes sure that the level is even.
- Display panel- It shows things like results, errors, information about how a function is set up, and “function in progress.”
- Draft shields– These are built into analytical balances to protect them from things like air flow and dust that could make the balance less accurate.
- Level adjustment feet- These make it possible to bring the balance back to the starting point. These legs can be moved. The reference point is set by the levelling bubble, spirit level, or plumb bob.
Important Parts of a Analytical Balance
- Balance plate (pan): It is the surface where the sample material to be measured is placed. It provides a stable platform for weighing.
- Weights: These are objects with known and fixed weights that are used for calibration purposes. They ensure the accuracy of the analytical balance.
- Draft shield: It is a transparent enclosure surrounding the balance plate. Its function is to protect the sample and container from external influences such as air currents and dust, which could affect the accuracy of the measurements.
- Door handle: It allows for easy access to the balance plate by opening and closing the draft shield when loading or unloading the sample.
- Level indicator: It helps to check if the balance is leveled properly. It ensures that the balance is on a stable and even surface for accurate weighing.
- Power button (on/off button): It is used to turn the balance on or off, activating or deactivating its functionality.
- ‘Re-zero’ or ‘Tare’ button: This button brings the balance back to a neutral or zero point. It allows for the removal of the weight of a container or additional materials placed on the balance, so the measurement can focus on the sample’s mass alone.
- ‘Mode’ button: It is used to set the measurement system or unit, such as grams (gm) or milligrams (mg). By pressing the ‘Mode’ button, the user can switch between different units of measurement as needed.
- Display panel: It is the interface that shows various information, including measurement results, errors, settings for different functions, and the progress of ongoing functions.
- Level adjustment feet: These are movable legs located at the base of the balance. They can be adjusted to bring the balance to a reference position or to ensure the balance is leveled properly.
Procedure for Operating Analytical Balance – Weighing Procedure of an Analytical Balance
1. Select a proper location
When selecting a location for an analytical balance, it is important to consider certain factors to ensure accurate and reliable measurements. Here are some guidelines to follow when choosing a proper location:
- Stability and Horizontal Surface: It is crucial to place the analytical balance on a stable and horizontal surface. This helps to prevent any vibrations or movement that could affect the balance’s performance. Uneven surfaces can introduce errors in the measurements, so ensure the balance is placed on a sturdy and level platform.
- Avoid Direct Sunlight and Temperature Changes: Direct sunlight can cause temperature fluctuations, which can affect the balance’s performance and accuracy. It is best to place the balance away from windows or areas with direct exposure to sunlight. Additionally, avoid locations with extreme temperature changes, as these can also impact the balance’s readings.
- Magnetic Interference: Magnetic or magnetic field-generating objects and equipment can interfere with the balance’s operation. It is important to keep the balance away from such objects to avoid any magnetic interference. This includes electronic devices, magnetic storage media, and strong magnetic fields.
- Dust-Free Environment: Dust particles can accumulate on the balance and affect its weighing accuracy. To minimize the impact of dust, choose a location that is as dust-free as possible. Avoid areas where there is excessive dust or ongoing activities that generate dust, such as nearby construction or manufacturing processes.
- Avoid Air Currents: Air currents can cause fluctuations in weight readings, especially in highly sensitive analytical balances. Keep the balance away from sources of air currents, such as ventilators, air conditioners, open doors, and windows. Even slight air movements can affect the balance’s measurements, so it is important to maintain a stable and calm environment.
By selecting a suitable location for the analytical balance, free from external disturbances and environmental factors, you can ensure consistent and accurate measurements. Taking these precautions helps to create an optimal weighing environment and minimizes potential sources of error.
2. Leveling the analytical balance
Leveling an analytical balance is essential to ensure accurate and precise measurements. Here are the steps to level the balance:
- Precise Horizontal Positioning: To achieve consistent and precise measurements, it is crucial to position the analytical balance horizontally. This means ensuring that the balance is level and free from any tilts or deviations.
- Adjusting the Leveling Feet: Most analytical balances are equipped with leveling feet, which can be adjusted to level the balance. Start by examining the leveling indicator on the balance. It typically consists of a bubble within a liquid-filled tube.
- Centering the Air Bubble: The goal is to adjust the leveling feet until the air bubble in the leveling indicator is perfectly centered. If the bubble is off-center, it indicates that the balance is not level.
- Adjusting the Leveling Feet: Begin by loosening the locking mechanism of the leveling feet, allowing them to be adjusted. Gently turn the leveling feet clockwise or counterclockwise to raise or lower the corresponding corners of the balance.
- Observing the Leveling Indicator: After making adjustments to the leveling feet, observe the leveling indicator again. If the air bubble is still not centered, continue adjusting the leveling feet until the bubble is precisely in the center.
- Locking the Leveling Feet: Once the balance is leveled and the bubble is centered, secure the leveling feet by tightening the locking mechanism. This ensures that the balance remains in its leveled position during weighing procedures.
By accurately leveling the analytical balance, you eliminate any potential deviations caused by an uneven surface. This allows for consistent and precise measurements, enhancing the reliability of your results. Regularly check the balance’s level and make adjustments as necessary to maintain optimal performance.
3. Calibrating the analytical balance
Calibrating the analytical balance is an important step to ensure accurate and reliable weighing results. Here are some key points to consider when calibrating the balance:
- Purpose of Calibration: The primary purpose of calibration is to establish the accuracy and precision of the analytical balance. Calibration compensates for any potential errors or deviations that may affect the weighing measurements. It is necessary to calibrate the balance under certain circumstances to maintain the integrity of the weighing process.
Circumstances Requiring Calibration: There are several circumstances that call for calibration of the analytical balance:
- Modifications to the usage location: If the balance is moved within the same room or to a different location, calibration is necessary due to potential changes in the environmental conditions.
- Alteration in the environment: Changes in temperature, humidity, or other environmental factors can impact the balance’s performance. Calibration is required to ensure accurate measurements in these changed conditions.
- Before each use: It is good practice to calibrate the analytical balance before each weighing operation to verify its accuracy and precision.
- Internal Calibration: Many analytical balances are equipped with internal calibration capabilities. This means that the balance has a built-in mechanism for calibration. Internal calibration requires manual input from the users to initiate the calibration process. The balance may provide prompts or instructions on the display screen for the user to follow. Internal calibration ensures that the balance is reset and adjusted to the desired accuracy.
- External Calibration: In addition to internal calibration, external calibration can also be performed on analytical balances. External calibration involves using an external calibration pendulum or weight set that has a known and precise mass. The calibration pendulum or weights are placed on the balance, and the readings are compared to the known values. Any discrepancies are then adjusted to align the balance with the correct measurements. External calibration provides an additional level of accuracy verification.
Regular calibration of the analytical balance is essential to maintain its accuracy and reliability. By calibrating the balance as needed, you can ensure that your weighing results are precise and traceable. Always follow the manufacturer’s instructions and guidelines for calibration procedures specific to your analytical balance model.
Weighing is a crucial step in using an analytical balance to determine the mass of a substance accurately. Here are the steps involved in the weighing process:
- Preheating: It is recommended to preheat the analytical balance for approximately an hour before using it. This ensures that the balance reaches a stable temperature and minimizes any potential temperature-related effects on the weighing process.
- Setting to Zero: Start by setting the analytical balance to zero in the no-load condition. This is done by pressing the “tare” button on the balance. Taring the balance accounts for the weight of the container or vessel used for weighing, ensuring that only the substance’s mass is measured.
- Placing the Container: Position the weigh boat, weigh paper, or any other vessel or container in the center of the weighing pan. Ensure that the container is clean and free from any debris. Close the glass door of the weighing chamber to protect the weighing process from external influences.
- Checking Stability: Once the container is placed on the balance, observe the displayed value on the balance. Wait for the value to stabilize and look for the stability mark, which indicates that the balance has reached a stable state. This ensures accurate and reliable measurements.
- Taring the Container: To exclude the mass of the container from the measurement, press the “TARE” button on the balance. This resets the balance’s reading to zero, effectively subtracting the weight of the container from the final measurement.
- Adding the Substance: After removing the container from the balance, carefully add the substance to be weighed into the container. Avoid placing objects directly on the balance pan, as it can introduce contamination and affect the measurement accuracy.
- Stabilization of Mass Reading: Once the substance is added, place the container back on the balance and ensure it is positioned properly. Reset the container’s tare and wait for the mass reading to stabilize. This typically takes 5-10 seconds, although it may take up to a minute for the reading to settle completely.
By following these steps, you can obtain accurate and precise measurements using an analytical balance. It is important to handle the substances and containers with care to avoid any errors or contamination during the weighing process.
Weighing a sample(s) that needs to be in a container or on a weighing paper:
- Open the glass door of the weighing chamber, position the container or weighing paper on the weighing pan, and then close the glass door.
- Wait until the display becomes stable.
- The presence of the stability symbol denotes a state of stability. The displayed value will then restore to zero when you hit “O/T.”
- Open the glass door, place the to-be-weighed sample(s) in the container/weighing paper, and then close the glass door.
- After the displayed value has stabilised, read it.
Regular cleaning is essential for maintaining the measurement accuracy and prolonging the lifespan of an analytical balance. Here are some important considerations when it comes to cleaning the balance:
- Use a gentle cleaning method: To clean the analytical balance, use a lint-free cloth that has been slightly dampened with a mild detergent solution. Make sure the cloth is free from lint to avoid any particles getting into the balance.
- Avoid abrasive or harsh chemicals: It is crucial to avoid using abrasive cleaning agents or harsh chemicals when cleaning the balance. These substances can damage the sensitive components of the balance and affect its performance. Organic solvents should also be avoided as they may react with the materials used in the balance.
- Cut off the power supply: Before starting the cleaning process, always turn off the power and unplug the balance from the electrical outlet. This ensures safety during cleaning and prevents any accidental electrical damage.
- Prevent liquid or dust from entering the balance housing: Take extra care to prevent any liquid or dust from entering the housing of the analytical balance. These contaminants can interfere with the sensitive components and compromise the accuracy of measurements. Clean the balance gently and avoid any excessive moisture that could seep into the internal parts.
- Clean the balance regularly: It is recommended to establish a regular cleaning routine for the analytical balance. The frequency of cleaning depends on the frequency of use and the nature of the substances being weighed. A clean balance will provide more accurate and reliable results.
By following these cleaning guidelines, you can ensure that your analytical balance remains in optimal condition and continues to deliver precise measurements. Regular cleaning helps to prevent buildup of contaminants and maintain the integrity of the balance for long-term use.
Removing the sliding glass doors for cleaning
- Take out the pan and the ring that stops air from getting in.
- Unscrew the inside knob on the glass door and pull it off.
- Pull the glass door backwards to open it.
Calibration Procedure of Analytical Balance
Calibrating an analytical balance is crucial to ensure accurate weight measurements. Here is a step-by-step procedure for calibrating an analytical balance:
- Check the manufacturer’s guidelines: Familiarize yourself with the specific calibration procedure recommended by the manufacturer of your analytical balance. This information can usually be found in the user manual or provided by the manufacturer.
- Gather the necessary equipment: Prepare the standard test weights that are known to have accurate calibration values. These weights should cover the range of measurements you typically perform on the analytical balance.
- Prepare the balance: Turn on the analytical balance and allow it to stabilize for the recommended warm-up time. This helps ensure that the balance is operating at its optimal condition for calibration.
- Zero the balance: Press the “tare” or “zero” button to reset the balance to zero in the no-load condition. This compensates for the weight of any containers or vessels used during the calibration process.
- Perform the calibration: Place the appropriate test weight on the balance pan according to the desired calibration value. Allow the balance to stabilize and display the measured weight.
- Compare the measured value: Compare the displayed weight on the balance to the known calibration value of the test weight. If there is a significant deviation, adjustment may be necessary.
- Make adjustments if needed: Some analytical balances have built-in internal calibration functions that allow you to adjust the calibration settings. Follow the manufacturer’s instructions for making any necessary adjustments.
- Repeat the calibration: It is recommended to repeat the calibration process with multiple test weights across the desired measurement range to ensure accuracy throughout.
- Document the calibration: Keep a record of the calibration procedure, including the test weights used, measured values, and any adjustments made. This documentation is essential for traceability and quality control purposes.
- Regularly recalibrate: It is important to regularly recalibrate the analytical balance to maintain accuracy. The frequency of recalibration depends on the specific requirements and regulations of your laboratory or industry.
By following a proper calibration procedure, you can ensure that your analytical balance provides accurate and reliable weight measurements for your scientific or analytical applications.
Types of Calibration
There are two ways to calibrate an analytical balance: from the inside and from the outside. And automatic calibration is a type of calibration that comes from internal calibration.
- Internal calibration is a feature available in certain analytical scales that allows for the calibration of the scale using built-in test weights. This method eliminates the need for external calibration weights and provides convenience and accuracy in the calibration process.
- Analytical scales with internal calibration capabilities often have a designated function or menu option that enables the internal calibration process. This feature allows the scale to be calibrated automatically at specific intervals by setting the time between calibrations. This ensures that the scale remains accurate and reliable without the need for manual calibration procedures.
- However, it is important to note that not all analytical scales have the capability for internal calibration. Some scales can only be calibrated externally using calibrated weights that are applied to the scale from the outside. In such cases, the calibration process involves adjusting the scale’s settings or making manual adjustments to align the measurements with the known calibration values.
- The availability of internal calibration functionality depends on the specific model and manufacturer of the analytical scale. It is recommended to refer to the user manual or consult with the manufacturer to determine if your analytical scale supports internal calibration.
- Internal calibration provides a convenient and efficient method for calibrating analytical scales, ensuring accurate measurements without the need for additional external weights. This feature simplifies the calibration process and helps to maintain the accuracy and reliability of the scale’s measurements.
External calibration is a calibration method used for analytical balances that involves the use of external test weights to calibrate the scale. There are two common types of external calibration: span calibration and linear calibration.
- Span calibration, also known as single-point or one-point calibration, involves using a single standard test weight that is equal to or close to the maximum capacity of the balance. During span calibration, the balance is adjusted to ensure that the measurement at the specified maximum capacity is accurate. This calibration method is relatively quick and straightforward but may not account for potential errors or inaccuracies at lower measurement ranges.
- On the other hand, linear calibration is a more comprehensive calibration method. It requires measuring a set of test weights, typically spanning the range of the balance’s measurement capacity. The balance is calibrated at different points using these test weights, and the measured data is used to create a calibration plot. The built-in program on the scale then uses this plot to calibrate itself, adjusting for any non-linearities or deviations from the ideal measurement curve. Linear calibration provides more accurate results across a wider range of measurements but requires additional test weights and a longer calibration process.
While both span calibration and linear calibration are effective methods, many experts consider linear calibration to be more accurate and reliable, particularly when precise measurements are needed over a broad range. Linear calibration takes into account potential non-linearities in the scale’s measurement response, resulting in more accurate and consistent measurements. However, it is important to note that linear calibration requires more test weights and longer calibration steps, which may increase the complexity and time required for calibration.
The choice between span calibration and linear calibration depends on the specific requirements of the weighing application. For applications that involve a narrow measurement range, span calibration may be sufficient. However, for applications that demand high accuracy and precise measurements across a wider range, linear calibration is generally recommended for optimal results.
Steps for internal calibration
Internal calibration is a calibration method that utilizes the built-in test weights of an analytical balance to calibrate the scale. Here are the steps typically involved in performing internal calibration:
- Consult the instruction manual: Begin by carefully reading and understanding the manufacturer’s instructions for setting up and calibrating the analytical balance. This will provide specific guidance tailored to the particular model of the balance.
- Warm-up period: Turn on the analytical balance and allow it to warm up for a recommended period of time, usually around an hour. This warm-up period ensures that the balance reaches a stable operating temperature, which is crucial for accurate measurements.
- No-load state: Ensure that the balance is in the “no-load” state, meaning there is no sample or object placed on the weighing pan. This ensures that the scale is ready for calibration without any external factors influencing the measurements.
- Initiate calibration mode: Locate the “CAL” button on the balance’s control panel. Press the “CAL” button, and the display will show “CAL-INT” or a similar indication, depending on the model. This signifies that the balance is ready to perform internal calibration.
- Automatic calibration: Once the calibration mode is activated, the internal calibration process will commence automatically. The built-in program of the balance will use the internal test weights to adjust and calibrate the scale based on predefined parameters. This calibration process ensures that the scale provides accurate and reliable measurements.
- Calibration completion: After the internal calibration is completed, the balance will automatically exit the calibration mode and return to the weighing mode. At this point, the scale is ready to be used for weighing samples, and it should provide accurate measurements based on the calibration performed.
Steps for external calibration
External calibration is a calibration method that involves using external test weights to calibrate an analytical balance. Here are the general steps involved in performing external calibration:
- Consult the instruction manual: Start by referring to the manufacturer’s instruction manual for the specific guidelines and procedures related to setting up and calibrating the analytical balance. This will provide detailed instructions tailored to the particular model of the balance.
- Warm-up period: Turn on the analytical balance and allow it to warm up for the recommended period of time, typically around an hour. This allows the balance to stabilize at the desired operating temperature, ensuring accurate measurements during calibration.
- Weighing state and zeroing: Ensure that the balance is in the weighing state, and make sure it is zeroed. This is usually done by pressing the “ZERO” or “TARE” button, depending on the balance’s control panel.
- Access calibration mode: Press the “ON” button on the control panel multiple times until the display shows “E-CAL” or a similar indication, depending on the model. This signifies that the balance is ready to enter the external calibration mode.
- Select calibration weight: Use the appropriate calibration weight specified in the instruction manual. For example, if the calibration requires a 200-gram weight, locate the 200-gram calibration weight.
- Confirm calibration weight: Press the “O/T” (Output/Tare) button to confirm the calibration weight selection. The display may show “CAL-200” or a similar indication, indicating that the balance is ready to receive the calibration weight.
- Place calibration weight on the scale: Carefully place the selected calibration weight, in this case, the 200-gram weight, on the weighing pan of the balance. Ensure that it is centered and properly positioned.
- Calibration confirmation: Once the calibration weight is placed on the scale, the display will show the calibrated weight value, such as “200.0000g” or a similar reading, confirming the calibration process for the external weight.
- Calibration completion: After the calibrated weight value is displayed, the external calibration is complete. The balance is now calibrated using the external test weight, and it should provide accurate measurements for subsequent weighing operations.
Verify a successful analytical balance calibration
- Drift check: Place the test weight in 10 different spots on the pan. Each measurement should fall within the error range.
- Performance check: Put 10 different test weights within the capacity range in the middle of the pan. Each measurement should be within the error range.
- Measurement Uncertainty check: Put a test weight within the capacity range in the same spot on the pan 10 times, write down the value of each measurement, and figure out the measurement uncertainty. The uncertainty should be within the given error range.
Rules For Analytical Balances
To ensure accurate and reliable mass measurements with a single-pan analytical balance, it is important to follow specific rules and guidelines. Adhering to these rules not only ensures accurate results but also helps maintain the integrity and performance of the balance. Here are the rules for using analytical balances:
- Close the balance door: While weighing an object, always keep the balance door closed. This prevents air currents from interfering with the reading. After use, close the door to protect the balance from dust and dirt.
- Suitable materials on the pan: Only place items made of glass, ceramic, metal, or plastic directly on the balance pan. These materials are appropriate for weighing and do not adversely affect the accuracy of measurements.
- Avoid touching objects: Refrain from touching objects that will be weighed with bare hands. Wet, greasy, or dirty fingers can alter the weight of the items and introduce measurement errors.
- Ensure room temperature: All items to be weighed must be at room temperature. Warm objects create convection currents inside the balance enclosure, leading to inaccurate readings. Warm air is less dense than the surrounding air, causing a negative determinate error.
- Use appropriate containers: Chemicals should not be placed directly on the balance pan. Instead, use suitable containers like beakers, flasks, or weighing bottles to hold liquids. This prevents any spillage or contamination of the balance.
- Consider desiccated objects: Objects or materials taken out of a desiccator may absorb moisture from the environment, making them heavier. To minimize this effect, record weights after a consistent time interval. For example, measure the weight of a crucible exactly 5 seconds after placing it on the balance pan. This helps mitigate the influence of moisture absorption.
- Avoid using paper: When using an analytical balance, paper should not be used for measuring weight. Paper can easily absorb moisture, affecting the accuracy of measurements. Instead, opt for appropriate weighing vessels or materials.
- Prevent chemical spills: It is crucial to prevent chemicals from entering the balance enclosure. In case of a spill, clean it up immediately to avoid any damage to the balance or interference with future measurements.
By following these rules, you can ensure accurate and reliable mass measurements with an analytical balance while also maintaining its performance and longevity. Always consult the user manual provided by the manufacturer for specific guidelines related to your analytical balance model.
Precautions for accurate sample weighing
To make sure your reports are correct, you must take the right precautions and follow the standard operating procedures.
1. Keep the balance calibrated
- First of all, make sure that the analytical balance is always in the right place. Standard reference weights are always used to compare the weights of samples. So, there must always be a set of certified standard weights in the lab.
- The scales’ calibration must be checked to make sure it meets the standards of a nationally recognised calibration lab. Keep the scale calibrated by following the standard procedures for calibration on a daily, weekly, and monthly basis.
- Never put your hands on the standard weights.
2. Ensure appropriate environment
- Use the built-in spirit level to make sure the balance is on a flat surface. Keep the balance in a place with no vibrations.
- Make sure you put the scales in a place where the humidity and temperature can be controlled. They shouldn’t be in direct sunlight, because that can cause the temperature inside the weighing chamber to change.
- Don’t put the scales next to doors or windows, because when you open or close them, air will flow past them. This could change how the weight is measured.
- Make sure the doors to the weighing chamber are closed before you weigh the samples. Lastly, keep the weighing chamber clean to keep samples from getting mixed up and getting wrong readings.
3. Handle the weights properly
- Don’t touch the weights with your bare hands, because the oil on your hands can mess up the readings. When putting the samples in place, you should always use a clean pair of forceps.
- Gently put the samples in the middle of the pan. Don’t leave the weights outside the workbench when you’re done with them. Keep them in the weight box’s slots and make sure the box is closed. This helps keep environmental exposure to a minimum.
- Use tweezers with rubber tips or tweezers made of wood to keep the weights from getting scratched. Wear gloves when you are moving heavy things.
- Don’t let the weights slip on the pans of the scales, because if they keep slipping, they will rub and wear down the base. This will make them weigh less, which will change how the scales read. Make sure they don’t run into anything hard.
4. Store the weights in the right manner
- Always keep the weights in a dry, dust-free room with no moisture or gases that could damage them. If the weights get rusty or if dust gets on them, their weight will go up. This will make the readings wrong.
- When you are done using the weights, put them in a desiccator to keep them dry.
5. Take the right measures to weigh the samples
- Place the sample with a clean spatula of the right size. Instead of using butter paper to measure the sample, use a volumetric flask to weigh it. The latter can lead to mistakes.
- Let the readings settle for a while before you write them down. Taking extra care is needed if you want to weigh small amounts of sample. For example, you could use disposable gloves and head caps to stop hair from falling out and a face mask to keep your breath from messing up the reading.
- Write the number down right away in the lab notebook. Don’t write the weight on scrap paper or your hands.
- Even a printer can be added to the balance. This will let you print the weight slips without making any mistakes when you type them.
Factors that affect readings on analytical balances
Analytical balances are highly precise instruments used in laboratory settings to measure the mass of substances with utmost accuracy. However, several factors can affect the readings on analytical balances, leading to fluctuations and potential inaccuracies. It is crucial to understand these factors and take appropriate measures to minimize their impact. Here are some key factors that can affect the readings on analytical balances:
- Temperature: Temperature fluctuations can have a significant impact on measurement accuracy. Changes in room temperature can cause expansion or contraction of the sample being weighed. An increase in temperature may lead to the evaporation of volatile substances or expansion of materials, while a decrease in temperature can cause condensation or contraction. To mitigate this effect, the temperature around analytical balances should be strictly controlled, and the room temperature should not fluctuate by more than a specified range, usually around 2 degrees.
- Vibrations: Vibrations in the environment can disrupt the precision of analytical balances. Sources of vibrations include footsteps, doors or cabinets banging, as well as equipment such as refrigerators or ventilation systems. Vibrations can cause samples to spill, move, or redistribute unevenly on the weighing pan, leading to measurement errors. It is essential to minimize vibrations in the weighing area and ensure the stability of the balance to obtain accurate readings. If significant vibrations occur, recalibration of the balance may be necessary, which can be time-consuming and incur additional costs.
- Chemical Reactions: Some samples are highly reactive and sensitive to atmospheric alterations. Chemical reactions can occur when volatile substances come into contact with the surrounding air, leading to changes in the composition or state of the sample. To avoid chemical reactions, samples to be weighed should remain chemically inert. Proper handling and storage techniques should be employed to minimize atmospheric exposure and ensure accurate measurements.
- Air Currents: Air movement or currents in the weighing environment can introduce variations in measurements. When air flows across the weighing pan, it can cause changes in air pressure, leading to fluctuations in mass readings. It is important to conduct weighing procedures in a well-ventilated room to minimize the influence of air currents. Controlling air currents through measures such as closing doors, minimizing air conditioning or fan usage during weighing operations, can help maintain measurement accuracy.
- Calibration: Calibration is essential for ensuring accurate readings on analytical balances. Regular calibration verifies the accuracy of the balance and corrects any deviations. Some analytical balances have internal calibration features that automate the calibration process with minimal user intervention. Others require external calibration using certified calibration masses and manual adjustment of calibration settings. Proper calibration procedures should be followed based on the specific requirements of the analytical balance and the laboratory environment.
- Magnetism: The magnetic properties of a sample can affect the measurements on an analytical balance. If the sample is magnetic or becomes magnetized, it can create a magnetic field that interferes with the balance’s sensor coil. This interference can lead to fluctuations and inaccuracies in the measurements. Special precautions should be taken when weighing magnetic samples, and alternative weighing methods may be required to obtain accurate results.
- User Errors: User errors, such as incorrect calibration, improper sample handling, or leaving samples exposed, can significantly impact measurement accuracy. Following standardized operating procedures and proper training for balance operation can help minimize user errors and ensure reliable results.
- Fingerprints: In cases where the sample size is very small, typically less than 0.1 mg, fingerprints can introduce unwanted mass and alter the measurement results. Care should be taken to avoid touching or contaminating samples with fingerprints, especially when dealing with highly sensitive or delicate materials.
- Humidity: Humidity levels can affect the performance of analytical balances. Low humidity levels can result in static electricity buildup, causing friction and affecting the accuracy of weight measurements. Maintaining appropriate humidity levels in the laboratory, typically around 40%, and ensuring anti-static measures, such as anti-static flooring and appropriate sample containers, can help mitigate the impact of humidity on measurement accuracy.
Understanding and addressing these factors that affect readings on analytical balances are crucial for obtaining reliable and precise measurements. By controlling environmental conditions, implementing proper calibration procedures, and following good laboratory practices, scientists can minimize the impact of these factors and ensure accurate results in their analytical work.
|Temperature||Fluctuations in room temperature can cause expansion or contraction of the sample, leading to measurement variations.|
|Vibrations||Vibrations from nearby equipment or environmental factors can disturb the balance, causing dislodgement or spilling of the sample and affecting the accuracy of the measurement.|
|Chemical Reaction||Highly reactive samples are sensitive to atmospheric changes, and their chemical reactions can alter the measurement. It is important to ensure that the sample remains chemically inert during weighing.|
|Air Currents||Air movement around the balance can result in variations in measurements. Proper ventilation and minimizing air currents in the weighing area are essential to obtain accurate readings.|
|Calibration||Regular calibration is necessary to maintain accurate readings. Analytical balances may have built-in internal calibration features or require external calibration using certified calibration weights.|
|Magnet||Magnetic samples or samples that are magnetized can create a magnetic field that interferes with the balance’s sensor coil, leading to fluctuations in measurement.|
|Fingerprints||In the case of very small sample sizes, fingerprints can have a significant impact on the measurement. Care should be taken to avoid touching the sample directly with bare hands to prevent contamination.|
Cleaning Procedure of Analytical Balance
- For analytical balances to work well, they need to be cleaned and cleaned the right way. If they aren’t, residues from the last time they were used can lead to wrong results and make the operator less safe.
- If you don’t clean the balance right, you could hurt the way it weighs and shorten its life. It is best to clean the scale right after each time it is used or when the substance is changed while it is being used.
- Always check how clean the area around the scale is to stop contamination from spreading. Keep the area clean and organised.
- Before cleaning, disconnect the scale from the power source.
- Protect your skin, nose, eyes, and mouth well with a coat, gloves, goggles, and masks, especially if any potentially toxic substances were left on the scale.
- Prepare the right cleaning tools, such as mild cleaning products, a lint-free cloth, and a microfiber towel that doesn’t scratch. Which cleaning agents to use depends on the kind and amount of dirt. People usually use water, window cleaner, 70% isopropanol, or ethanol. Don’t use organic solvents or rough ingredients that could hurt the balance in the long run.
- First, you need to turn off the balance display.
- Clean the housing for the balance.
- Use a disposable tissue or a lint-free cloth dampened with mild detergents to clean the surface of the scale and get rid of the powder, dust, and sticky things on it. Make sure not to scratch anything.
- Clean the draft shield: Since the draught shield is made of glass, it is easy to clean with a damp cloth or soft paper tissue, a mild detergent, or a commercial glass cleaner.
- Clean the removable parts: Take out the weighing pan, pan support, and winding ring from the scales and clean them with a damp cloth or tissue. Don’t wipe them down on the scale. Only take apart the parts that the operating instructions say you can. Once the parts you took off are dry, carefully put them back where they belong.
- Clean the weighing chamber: Carefully wipe away dust and powder with a damp, lint-free cloth before cleaning the weighing chamber. Never blow, because it could move dust or sample materials into the hole in the middle of the weighing chamber, where there are internal circuits and electromagnetic force cells. If dust or liquid gets into the circuits, they might not work right, making the readings unstable.
- Please note that you can’t clean the control panel, power plug, data interface, labels, or any plastic parts like draught shield handles and frames with acetone or other harsh cleaners.
- Reassemble the balance and return all removed components to their original locations.
- Turn on the scales with sufficient warm-up time.
- Complete the balance’s level adjustment and calibration.
- Perform a weight test and verify the precision.
- After cleaning the balance, cover it with a dust cover to prevent dust and moisture from entering the weighing chamber.
- Cleaning the analytical balance is simple and quick. In addition to the general guidelines listed above, be careful to study the operation handbook of your analytical balance, which provides more specific cleaning instructions and precautions.
Use of analytical balance
An analytical balance is a precise instrument that finds application in various fields for a range of tasks. Here are some common uses of an analytical balance:
- Analysis and determination of density: Analytical balances are utilized in determining the density of substances by accurately measuring the mass of a given volume. This information is crucial for numerous scientific and industrial applications.
- Preparation of samples: Analytical balances are essential in sample preparation, where precise measurements are required to achieve accurate results. They are used to measure and portion out precise quantities of substances for further analysis or experimentation.
- Pipette calibration: Analytical balances play a crucial role in calibrating pipettes. By accurately weighing the dispensed liquid, the balance ensures the pipette delivers the intended volume and helps maintain the accuracy of volumetric measurements.
- Differential weighing: In applications where small changes in mass need to be detected, such as in quality control or formulation development, an analytical balance is used for differential weighing. It can accurately measure the difference in mass before and after a specific process or reaction.
- Piece counting: Analytical balances equipped with piece counting functionality enable the determination of the quantity of small items based on their weight. This is useful in inventory management, packaging, or manufacturing processes.
- Interval weighing: When dealing with substances that are susceptible to evaporation, an analytical balance can be used for interval weighing. By measuring the weight at specific time intervals, the rate of evaporation can be determined.
- Formulation/Recipe calculation: Analytical balances are employed in formulating recipes or determining ingredient proportions in various industries such as pharmaceuticals, cosmetics, and food. Precise weighing ensures accurate formulation and consistent product quality.
- Percent weighing: In analytical chemistry, percent weighing is crucial for determining the composition or concentration of a sample. An analytical balance enables accurate measurement of the sample and the necessary components to calculate the percentage composition.
- Filling: Analytical balances are utilized in filling operations, where precise amounts of substances are dispensed into containers. The balance ensures accurate filling, minimizing variations and ensuring product consistency.
- Gross-net tare weighing: Analytical balances feature a tare function that allows the subtraction of the weight of containers or vessels. This facilitates the measurement of the net weight of the substance being weighed without considering the weight of the container.
- Checkweighing: Analytical balances can be used for checkweighing, which involves verifying whether the weight of a sample or product falls within specified limits. It is commonly used in quality control processes to ensure compliance with weight standards.
- Animal weighing: Analytical balances with higher capacity can be used for weighing small animals in research laboratories or veterinary clinics. This enables accurate monitoring of the animals’ growth, health, or drug dosage requirements.
These are just a few examples of the diverse applications and uses of analytical balances. Their precision, accuracy, and ability to measure small quantities make them indispensable in scientific research, quality control, manufacturing processes, and other fields that require precise weighing.
Advantages of Analytical Balance
Analytical balances offer several advantages that make them highly valuable in various applications. Here are some key advantages of analytical balances:
- High degree of accuracy: Analytical balances are designed to provide exceptional accuracy in measuring the mass of objects. They can measure small masses with precision, often up to four decimal places, ensuring reliable and precise results.
- Quick and efficient measurement: Analytical balances are known for their speed and efficiency in determining an object’s mass. With their user-friendly interface and intuitive operation, they enable quick measurements, saving time in laboratory and industrial settings.
- Self-calibration system: Many modern analytical balances feature a self-calibration system that ensures the scale is always correctly set and produces the most precise results. This weight adjustment mechanism allows for easy calibration, eliminating the need for external calibration weights.
- Sensitivity to small weight variations: Analytical balances have the ability to detect even the smallest weight variations. This sensitivity is essential in applications where precise measurements are required, such as in analytical chemistry, pharmaceutical research, and quality control processes.
- Support for good laboratory practices (GLPs): Analytical balances assist laboratories in upholding and enhancing good laboratory practices. By providing accurate and reliable measurements, they contribute to the overall quality, consistency, and integrity of laboratory procedures and data.
- Uniformity, consistency, and reproducibility: The use of analytical balances ensures uniformity, consistency, and reproducibility in measurement. By providing precise and consistent results, they help maintain quality standards and facilitate reliable data analysis and interpretation.
- Enhanced precision through electronic leveling: Some analytical balances incorporate electronic leveling features that improve precision. These instruments can detect any tilting or misalignment and provide visual alerts and guided leveling instructions to ensure accurate measurements.
- Easy to use: Analytical balances are designed to be user-friendly, making them accessible even to inexperienced users. With their intuitive menus and clear displays, users can quickly become familiar with the instrument’s operation and maximize its potential.
- Non-contact weighing and reduced contamination risk: Analytical balances equipped with non-contact infrared (IR) sensors simplify weighing tasks and reduce the risk of contamination. By eliminating the need for direct contact with the weighing surface, these balances help maintain sample purity and minimize cross-contamination.
In summary, analytical balances offer a high degree of accuracy, efficiency, and reliability in mass measurement. Their self-calibration systems, sensitivity to small weight variations, and support for good laboratory practices make them indispensable tools in laboratories, research facilities, and industrial settings. Their user-friendly nature and ability to ensure uniformity and reproducibility further enhance their value in various applications.
Limitations of Analytical Balance
While analytical balances offer numerous advantages, they also have certain limitations that users should be aware of. Here are some limitations of analytical balances:
- Sensitivity to environmental factors: The accuracy and precision of analytical balances can be affected by environmental factors such as temperature, air currents, humidity, and vibrations. Fluctuations in these factors can result in variations in readings and compromise the reliability of measurements.
- Unsuitable for rigorous measurements: Analytical balances are generally not intended for use in highly rigorous measurements that require extremely precise and accurate results. They are better suited for applications where a high level of precision is necessary but not to the extent of ultra-precise measurements.
- Delicate nature: Analytical balances are delicate instruments that require careful handling. They are sensitive to impacts, rough handling, and excessive force, which can affect their performance and accuracy. Users should exercise caution and follow proper handling procedures to avoid damaging the balance.
- Vulnerability of LCDs to heavy loads: The liquid crystal displays (LCDs) used in analytical balances can be easily damaged if heavy loads are placed on the weighing pan. Excessive weight can put strain on the LCD, leading to display malfunctions or permanent damage. Users should adhere to the balance’s maximum weight capacity to avoid such issues.
- Limited capacity for large quantities: Analytical balances are designed for measuring small quantities of substances with high precision. They are not suitable for measuring large quantities due to their limited weight capacity. If larger quantities need to be measured, alternative weighing instruments or methods should be employed.
- Dependency on environmental conditions: As previously mentioned, the accuracy and precision of measurements with analytical balances depend on environmental factors. Variations in temperature, air currents, and other conditions can introduce errors and affect the reliability of results. Adequate measures should be taken to control and stabilize these environmental factors during weighing procedures.
- Complexity of multi-component samples: Analytical balances may face challenges when weighing multi-component samples, especially when the individual components have significantly different densities or properties. Achieving accurate measurements in such cases requires careful consideration of the sample preparation and handling techniques.
Despite these limitations, analytical balances remain valuable tools for precise and reliable mass measurements within their designated capacity and application range. By understanding these limitations and taking appropriate precautions, users can maximize the effectiveness and accuracy of their weighing processes.
Difference Between Internal Calibration Vs External Calibration
- As a precision weighing device, analytical balances, particularly high-precision analytical balances used in laboratories of research institutes and pharmaceutical firms, must always be accurate in order to generate correct and consistent data.
- Frequent calibration is required to ensure the accuracy of the analytical balance.
- External calibration and internal calibration are the two types of calibration.
- The calibration weight that comes with the analytical balance is used for external calibration. Analytical balances that have been around for a long time usually come with a calibration weight. The weight of this weight depends on how much the analytical balance can hold. For example, if you buy a 0.1mg analytical balance that can hold 210g, you will usually get a 200g calibration weight.
- There are buttons on the analytical balance that can be used to calibrate the weight. Step one is to press a button to get into the calibration mode. Step two is to put the calibration weight on the weighing pan and press a button to calibrate the scale. As soon as the calibration is done, a signal will show up on the screen.
- Take, for example, the U.S. Solid USS-DBS83 Analytical Balance. To do the external calibration, turn on the scale and press the “CAL” and “ON” keys at the same time to enter linear calibration mode. Then, follow the on-screen instructions to place the 200g, 150g, 100g, and 50g calibration weights in order to calibrate. The linear calibration will be done when all the weights are calibrated.
- Internal calibration is a method of calibration that is more advanced. The analytical balance has built-in weights and automatic calibration programmes so that it can be used to calibrate itself. Usually, the scale has an internal calibration button. When the scale needs to be calibrated, all you have to do is press that button, and the scale will do it for you. You won’t have to take the time and trouble to calibrate such a scale.
- As an example, we’ll look at the U.S. Solid USS-DBS47 Analytical Balance. Press the “CAL” button when the balance is in the “no-load” state, and “CAL-INT” will flash on the screen. Then, the scale will automatically calibrate itself on its own.
- Most analytical balances that can be calibrated internally also have a function that can do the calibration for them automatically. The user sets the time interval for automatic calibration, and the balance will be calibrated automatically at each point in the time interval. If you choose the “30-minute” option, for example, the analytical balance will be calibrated automatically every 30 minutes.
- Analytical balances that can be calibrated internally will also be able to be calibrated externally, but they may not come with a calibration weight.
|External Calibration||– Uses a separate calibration weight provided with the analytical balance.
– Manual process that requires user intervention.
– Weight is placed on the weighing pan and specific buttons are pressed to initiate calibration.
– Balance compares the weight of the calibration weight to its internal reference and makes adjustments for accurate measurements.
|Internal Calibration||– More advanced method with built-in weights and automated calibration programs.
– Analytical balance calibrates itself without the need for external weights.
– Typically has an internal calibration button or function to initiate the automatic calibration process.
– Balance uses its internal reference weights and algorithms for calibration.
|Automatic Calibration||– Available in analytical balances with internal calibration functionality.
– User sets a time interval for automatic calibration (e.g., every 30 minutes).
– Balance calibrates itself automatically at the specified intervals.
– Ensures continuous accuracy without requiring manual calibration each time.
|Compatibility with External Calibration||– Analytical balances with internal calibration capability can also be calibrated externally if needed.
– May not come with a separate calibration weight since they rely on internal calibration mechanisms.
Difference between an Analytical Balance and a Precision Balance
- Analytical balances are made to measure small amounts of mass with a high level of accuracy.
- Analytical balances are usually used for quantitative chemical analysis. They are very sensitive and can measure to four decimal places to the right of the decimal point. They can measure samples that weigh up to 320g.
- The measurement on an analytical balance is so sensitive that air currents can change it. A draught shield is there to keep the readings from being wrong.
- To keep the environment from getting in the way, a space should be set aside.
- Analytical balances need to be calibrated often and carefully watched over.
- Most scales have an internal motorised calibration weight that adjusts itself automatically.
- Calibration can also be done with weights from the outside.
- These scales are used in the fields of chemistry and medicine.
- Precision scales, which are also called “top-loading scales,” can measure up to 200 grammes and cost less than analytical scales.
- These balances are considered semi-analytical because they are not as accurate as a standard analytical balance and can only be read to three decimal places to the right of the decimal point.
- They are also unaffected by the environment and give a reading in a matter of seconds.
In conclusion, an analytical balance is a better choice for your lab if you need a lot of accuracy. The accuracy of an analytical balance is between 0.0001 and 0.00001g. If it’s not important to be very precise, a top-loading scale will work just fine to measure 0.001g. There are many other kinds of balances on the market that aren’t talked about in this article. But you should look into the following if an analytical or precision balance doesn’t work for your lab.
|Aspect||Analytical Balance||Precision Balance|
|Purpose||Designed for measuring small masses||Used for general-purpose weighing tasks|
|Accuracy||Offers high accuracy, typically up to 4 decimal places||Provides lower accuracy, usually up to 3 decimal places|
|Maximum Capacity||Can handle samples weighing up to 320g||Can measure up to 200g|
|Sensitivity to Environment||Highly sensitive to environmental factors such as air currents||Not as sensitive to environmental factors|
|Draught Shield||Equipped with a draught shield to prevent air currents from affecting measurements||Typically does not require a draught shield|
|Calibration||Requires frequent and careful calibration||Calibration can be done internally or externally|
|Cost||Generally more expensive than precision balances||Usually more affordable compared to analytical balances|
|Applications||Commonly used in quantitative chemical analysis and research||Suitable for general laboratory weighing tasks|
|Accuracy Range||Offers higher accuracy range (0.0001g to 0.00001g)||Provides lower accuracy range (0.001g)|
Video guide of Analytical Balance
Analytical Balance Examples
1. Analytical laboratory balance XPR (Manufacturer: Mettler Toledo)
The XPR Automatic Balance manufactured by Mettler Toledo offers exceptional weighing accuracy that surpasses human methods. It has a readability of 2 g, allowing for precise dispensing of incredibly small sample quantities, thereby minimizing the use of expensive and rare materials. The automated approach minimizes the impact of external sources of error, ensuring time efficiency and highly reproducible results. Built-in sensors enable dispensing into even the smallest tare containers, eliminating sample transfer and associated errors.
2. BA-B Series Electronic Analytical Balance (Manufacturer: Biobase)
The BA-B Series Electronic Analytical Balance by Biobase features an innovative design with a five-sided fully transparent windscreen and a humanized design. It utilizes a latest-generation electromagnetic balance weighing sensor, ensuring high precision. The balance comes with application programs such as four-point linear calibration, automatic fault detection, and overload protection. The ultra-large LCD provides a sharp and comfortable visual experience.
3. Analytical laboratory balance AS 62/220.R2 (Manufacturer: Radwag Balances and Sales)
The AS 62/220.R2 analytical balance manufactured by Radwag Balances and Sales has a maximum capacity of 60/220 g and a readability of 0.01/0.1 mg. The AS R2 PLUS model stands out with its contemporary constructional and system solutions, ensuring reliability, precision, and measurement accuracy while simplifying daily use. The balance features a roomy weighing chamber and an open-door clearance, allowing easy access to the weighing pan. Innovative building techniques enhance the balance’s long-term dependability and longevity. The leveling mechanism located in front of the weighing chamber facilitates level control.
4. Analytical laboratory balance 390 (Manufacturer: Precisa Gravimetric AG)
The Analytical laboratory balance 390 by Precisa Gravimetric AG offers high-end weighing capabilities with an optimized electrical control and high resolution weighing cell. It features a strong sheet metal housing with a die-cast aluminum base, providing durability. The balance comes with a 7″ anti-reflective, high-resolution touch screen that is UV resistant, authorized for use with common laboratory gloves, shock and scratch resistant, and frameless for easy cleaning. The balance also incorporates a context help feature, providing relevant support and assistance based on the current context. It includes a draft shield that can be operated mechanically, electronically, or touch-free using a special sensor. The balance further offers a fully automatic, programmable, and temperature-controlled internal self-linearization and calibration system (SLS).
What is the minimum load weighed on analytical balance?
A basic rule of thumb states that to weigh 1 milligramme of sample, at least a 0.0001 g (Four Place) balance is required. This may still not be sufficient. We propose a minimum load of 10 milligrammes for our four-position balances (mg). Or 0.0100 g to ensure accurate measurements.
What Is Mass?
Mass is a constant measure of how much matter something has. No matter where you measure it, it’s always the same. The kilogramme and the gramme are the most common ways to measure mass.
What Is Weight?
The heaviness of an item is its weight. It is proportional to the item’s gravity multiplied by its constant mass. Due to differences in gravity, the weight of an object at the summit of a mountain will be less than the weight of the same object at the base. The newton is a unit of measurement for weight. A newton accounts for an object’s mass and relative gravity to determine its total force, which is weight.
Although mass and weight are distinct concepts, the process of ascertaining both is referred to as weighing.
What is Accuracy?
The capacity of a scale to produce results that are as close to the actual value as possible. When comparing masses of one kilogramme, the accuracy of the best current balances exceeds one part in one hundred million.
What is Calibration?
The comparison between a scale or balance’s output and a standard value. Typically performed with a known reference weight and adjusted so the device delivers a consistent reading.
What is Capacity?
The maximum load that the equipment can measure.
What is Precision?
Repeatability is the degree of agreement between repeated measurements of the same quantity. A scale may be exceptionally precise but not necessarily accurate.
What is Readability?
This is the smallest division that can be read on the scale or balance. It might range from 0.1g to 0.0000001g. The readability of a scale refers to the number of places following the decimal point that can be read.
What is Tare?
The process of removing a known weight of an object, often the weighing container, from a scale in order to zero it. This indicates that the final reading will reflect the weight of the material being weighed and not the weight of the container. The majority of balances permit tagging to capacity.
What is the difference between accuracy and precision?
Accuracy indicates how well a scale approximates the actual value. A faulty scale provides a reading that is not near to the actual value. Precision and accuracy are distinct concepts. Repeatedly weighing the same object on a precise scale will get the same result. A precise scale can be unreliable if it consistently returns values that are far from the actual value. For instance, a scale that reads 5.2g for the same item three times in a row is quite exact, but if the item truly weighs 6.0g, the scale is not accurate.
What is the use of analytical balance?
Analytical balances are precision measuring instruments used in quantitative chemical analysis, to determine the mass of solid objects, liquids, powders and granular substances.
What are the various parts of an analytical balance?
The various parts of an analytical balance are Balance plate (pan), Weights, Water pass, Power button (on / off button), ‘Re-zero’ or ‘Tare’ button, ‘Mode’ button
- Proper Use of Balances. (2022, August 17). California State University Dominguez Hills. https://chem.libretexts.org/@go/page/74518