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Analytical Balance – Diagram, Principle, Parts, Types, Uses

What is Analytical Balance? An analytical balance is a highly sensitive laboratory equipment that measures mass with a high degree of precision...

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This article writter by MN Editors on September 29, 2022

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Analytical Balance - Diagram, Principle, Parts, Types, Uses
Analytical Balance - Diagram, Principle, Parts, Types, Uses

Contents

What is Analytical Balance?

  • An analytical balance is a highly sensitive laboratory equipment that measures mass with a high degree of precision in the sub-milligram range. The weighing capacity of analytical balances ranges from 100 to 500 g, and their readability ranges from 0.1 mg to 0.001 mg.
  • Analytical balances have a draught shield or weighing chamber in the shape of a transparent cage to prevent air currents and dust from interfering with the operation of the balance. Use of analytical balances should be restricted to trained persons exclusively.
  • In terms of readability, an analytical balance differs from a precision balance. Analytical balances have a higher readability (0.0001g) than precision balances (0.001g), and are consequently more expensive.
  • “balance” is derived from the Greek word “bilanx,” which means “two-pans.” According to the National Institute of Health, the earliest known balances date back to 5,000 B.C. (NIH).
  • From antiquity until the 1950s, laboratories measured weight with two-pan balances. Invention of the single-pan balance in the 1950s led to its widespread adoption. Today, electronic balances are used in laboratories.
  • Weight is a force imposed by gravity on an item, whereas mass is the amount of matter in an object. At various locations, weight varies although mass is always constant.
  • While the mass of an object is measured in grammes, the phrases weight and weighing are employed.
  • Two-pan and single-pan balances use a reference mass (or substitute weight) to determine the mass of an object whose mass is unknown. Additionally, electronic balances utilise reference weight to calibrate a weight prior to an exact measurement.
  • Brass and bronze, plated with either chromium or lacquer, are used to create reference weights exceeding one gramme. These weights range from one to one hundred grammes.
  • The fractional reference weights are constructed of aluminium or platinum. These weights vary between 500 mg and 5 mg.

Principle of Analytical Balance

  • Balances do not measure mass directly; rather, they measure the force (weight) acting downward on the pan of the balance.
  • The majority of analytical balances are electromagnetic balances, therefore this weight is measured with an electromagnet.
  • The electromagnetic servomotor that generates a force against the measured mass’s weight.
  • With proper calibration, the electrical current required to generate this force is proportional to the mass and may therefore be used to calculate the mass.
  • This quantity is then presented on the screen.
  • Many balances contain a “null detector” that employs a light source and detector to indicate when the weight and electromagnetic forces are equal.
  • Due to the usage of electromagnetic forces, balances that have been turned off (at the wall) should not be utilised immediately after being reactivated.
  • At least thirty minutes must pass for the electromagnetic field to stabilise (times may vary depending on manufacturer and model).
  • This also implies that placing any magnetic materials or magnets close to the balance could cause it to malfunction.
diagram of analytical balance
diagram of analytical balance

Types of Balances and Scales

Types of Balances and Scales
Types of Balances and Scales

1. Analytical Balance 

  • These are typically found in laboratories or other locations where the weighing of objects requires exceptional precision.
  • Analytical balances are used to measure mass.
  • The results of chemical analysis are always based on mass, therefore they are not affected by the gravity at a particular site, which would influence the weight. Typically, an analytical balance’s capacity spans from 1 g to a few kilogrammes, and its precision and accuracy frequently exceed one part in 106 at full capacity.
  • An analytical balance consists of numerous crucial components. A beam arrest is a mechanical device that prevents damage to the pan’s delicate internal components when placing or removing things.
  • On a balance, an object is placed in the pan in order to be weighed.
  • Leveling feet are legs that can be adjusted to bring the balance to the reference position.
  • An vital aspect of the balance, the spirit level, levelling bubble, or plumb bob determines the reference position.
  • Even air currents can impact the accuracy of an analytical balance’s reading.
  • They must be protected against this by a draught shield. This is an enclosure made of plastic or glass with doors that provides access to the pan.

2. Equal Arm Balance/Trip Balance

  • This is the contemporary equivalent of ancient Egyptian scales.
  • This sort of laboratory scale consists of two pans positioned on opposite sides of a lever.
  • It has two separate applications. On one side, the object to be weighed is placed, and on the other, standard weights are added until the pans are balanced. The mass of the object is equal to the sum of the standard weights.
  • Place two objects on each scale, and then adjust one side until both pans are levelled. This is useful for applications such as balance tubes or centrifugation in which two things must have the exact same mass.

3. Platform Scale 

  • This sort of scale has a multiplicative lever mechanism.
  • It permits the placement of a heavy object on a load-bearing platform. The weight is subsequently transferred to a beam that can be balanced by repositioning a counterpoise, a part of the scale that counterbalances the weight on the platform.
  • This type of scale is utilised for applications such as weighing drums and even animals in a veterinarian’s practise.

4. Spring Balance 

  • This sort of balancing employs Hooke’s Law, which asserts that the spring’s tension is proportionate to its strain.
  • Spring balances are composed of a highly elastic, helical, hard-steel spring suspended from a fixed point.
  • The weighing pan is affixed to the spring’s lowest position.
  • The weight measurement is indicated via an indicator, and no human adjustment of weights is required.
  • Produce-weighing scales in grocery stores are an illustration of this type of scale.

5. Top-Loading Balance 

  • This is another scale that is mostly used in laboratories.
  • Most of the time, they can measure things that weigh between 150 and 5000 g.
  • They aren’t as easy to read as an analytical balance, but they can measure quickly, making them a better choice when exact measurements aren’t necessary.
  • The cost of top-loaders is also less than that of analytical balances.
  • Modern top-loading scales are powered by electricity and can give a digital reading in just a few seconds.

6. Torsion Balance 

  • The amount of twisting in a wire or fibre is used to figure out how big something is.
  • Torsion balances are used in many microbalances and ultra-microbalances that measure fractions of grammes. Quartz crystal is a well-known type of fibre.

7. Triple-Beam Balance 

  • This type of lab scale is not as accurate as a top-loading scale.
  • They are often used in the classroom because they are cheap, easy to use, and last a long time.
  • They are called triple-beam balances because they have three rows of weights that slide along scales that are each set to a different level.
  • Most of the time, the three decades have steps of 100g, 10g, and 1g. These scales are much harder to read, but they work well for most weighing tasks.

8. Semi Micro, Micro & Ultra Micro Balances

  • Ultra micro and micro balances are used to weigh the smallest amounts.
  • Most of the time, these scales can measure down to 0.1 g or 0.00001 g, which is between 3 and 10 grammes.
  • Most of the time, these types of scales have two parts. One part has the electronics, and the other part has the measuring cell.
  • This will make it harder for the electronics to affect how much the sample weighs. Uses for these types of scales include weighing particles or filters, calibrating pipettes, drying, ash-making, and measuring coatings.
  • Ultra micro balances have 7 digits, micro balances have 6 digits, and semi-micro balances have 5 digits.

Parts of Analytical Balance

  1. 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.
  2. 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.
  3. 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.
  4. 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.
  5. 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.
  6. ‘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.
  7. ‘Mode’ button: used to set the system that is used to measure. You can change the conversion system by pressing the “Mode” button.
  8. Level indicator- It makes sure that the level is even.
  9. Display panel- It shows things like results, errors, information about how a function is set up, and “function in progress.”
  10. 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.
  11. 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.
analytical balance diagram
analytical balance diagram

Operating Procedure of Analytical Balances

1. Select a proper location

How well an analytical balance works for measuring depends a lot on its surroundings. To make sure the right conditions are in place, you need to do the following:

  • Choose a place that is firm, flat, and free of vibrations.
  • Avoid direct sunlight and make sure that the temperature doesn’t change too much.
  • Don’t let air currents from air conditioners, fans, open doors or windows, or ventilation systems affect you.
  • Stay away from things that are magnetic or have the ability to make magnetic fields.
  • As much dust as possible should be cleaned up.

2. Leveling the analytical balance

  • For repeatable measurements and exact results, the horizontal position must be correct.
  • The analytical balance needs to be levelled to make up for small differences or tilts in this spot. Set the analytical balance’s levelling feet so that the air bubble in the indicator is in the middle.

3. Calibrating the analytical balance

Calibration is required to ensure that the sample will be accurately weighed by the analytical balance. Carry out calibration procedures in the following instances:

  • Variations in the place of use (including moving in the same room).
  • Changes in the environment
  • Before each use.

4. Weighing

  1. Before using, one hour of preheating is recommended.
  2. Zero out the analytical balance in the state of no load.
  3. After placing the sample(s) on the weighing pan, close the glass door of the weighing chamber.
  4. After the displayed value has stabilised, read it. The presence of the stability symbol denotes a state of stability.

Weighing a sample(s) that needs to be in a container or on a weighing paper:

  1. Open the glass door of the weighing chamber, position the container or weighing paper on the weighing pan, and then close the glass door.
  2. Wait until the display becomes stable.
  3. The presence of the stability symbol denotes a state of stability. The displayed value will then restore to zero when you hit “O/T.”
  4. Open the glass door, place the to-be-weighed sample(s) in the container/weighing paper, and then close the glass door.
  5. After the displayed value has stabilised, read it.

5. Cleaning

  • The analytical balance works better and lasts longer if it is cleaned on a regular basis.
  • Use a piece of lint-free cloth that has been dampened with soap to clean the analytical balance.
  • To clean, turn off the power switch and take out the power cord.
  • Make sure that neither dust nor liquid can get into the housing of the analytical balance.
  • Do not clean the analytical balance with aggressive cleaning agents (solvents, abrasive cleaning agents, etc.) or organic solvents.

Removing the sliding glass doors for cleaning

  1. Take out the pan and the ring that stops air from getting in.
  2. Unscrew the inside knob on the glass door and pull it off.
  3. Pull the glass door backwards to open it.

Calibration Procedure of Analytical Balance

  • In calibration, the measured value from the analytical balance is compared to a standard test weight whose accuracy is known.
  • One of the best things about calibrating an analytical balance is that it will give you accurate weight results. We will talk about how to calibrate an analytical balance in this article.
  • On the one hand, the calibration of the scale could be changed during shipping, even if it had already been done by the manufacturer. On the other hand, things like temperature, humidity, barometric pressure, altitude, gravitational acceleration, and etc. could change how well the analytical balance works. So, an analytical balance needs to be set up before it can be used.

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

  • With internal calibration, the built-in test weights can be used to calibrate the scales from the inside.
  • Most of these kinds of scales can even be calibrated automatically by setting the time between calibrations.
  • Not every analytical scale has a way to calibrate itself on the inside. The common ones can only be set up from the outside.

External calibration

  • There are two types of external calibration: span calibration and linear calibration.
    • For span calibration, you use one standard test weight that is equal to or close to the balance’s maximum capacity. It’s also called single-point or one-point calibration.
    • For linear calibration, you have to measure a set of test weights one after the other.
  • Then, the built-in programme on the scale will plot the measured data and calibrate itself based on the plot.
  • Most people agree that linear calibration is better than single-point calibration because it works better over a wider range. Still, linear calibration does need more test weights and longer steps.

Steps for internal calibration

  1. Follow the instructions in the manual to set up the scale.
  2. Turn it on and give it an hour to warm up.
  3. When the balance is in the “no-load” state, press the “CAL” button and “CAL-INT” will show up.
  4. Then the scale will start to calibrate itself automatically.
  5. After calibration, the scale will go back to weighing.

Steps for external calibration

  1. Follow the instructions in the manual to set up the scale.
  2. Turn it on and give it an hour to warm up.
  3. In the weighing state, set the scale to zero.
  4. Press the “ON” button a few times in a row until “E-CAL” appears on the screen.
  5. To confirm, press the “O/T” button, and “CAL-200” will flash on the screen.
  6. Put the 200-gram calibration weight on the scale.
  7. Then the number “200.0000g” will be shown. Calibration on the outside is done.

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

With a single-pan analytical balance, the following rules describe the steps that must be taken in order to get accurate and reliable mass measurements. By following these rules, you will also keep the balance from getting worse.

  • Close the door of the scale while you’re weighing something to keep air currents from messing up the reading. When the operator is done, he or she should close the balance door to keep dust and dirt from getting inside.
  • Only things made of glass, ceramic, metal, or plastic should be put directly on the pan of the balance.
  • Don’t touch things that will be weighed with your bare hands. If your fingers are wet, greasy, or dirty, the weight of the objects will change.
  • All items must be at room temperature in order to be weighed correctly. When an object is warm, it creates convection currents inside the enclosure of the scale. This makes an object look lighter than it really is. Also, warm air inside the enclosure is less dense than the air it pushes out, which also causes a negative determinate error.
  • Never put chemicals you want to weigh right on the pan of the scale. Use things like beakers, flasks, and weighing bottles to hold the liquid.
  • All objects and materials that have just come out of a desiccator will soak up water and get heavier because of it. So, it is a good idea to write down weights after the same amount of time. For example, if you are trying to get the weight of crucibles to stay the same. Always write down the crucible’s weight exactly 5 seconds after putting it on the balance pan. Using this method, you can reduce the effect of water getting into something.
  • When using an analytical balance, you should never use paper to measure weight.
  • Don’t get chemicals inside the enclosure of the scale. If something gets spilled, clean it up right away.

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

Because analytical balances are so accurate (they can measure to four decimal places), they are very sensitive to outside noise and to how they are set up and used. This makes it harder to read the lab balance, which could lead to wrong results.

  1. Calibration – The best way to check how accurate a scale is is to calibrate it. It makes sure that the results are always correct, accurate, and repeatable.
  2. Temperature – Temperature changes in the environment and in the equipment used to weigh things can cause the readings on laboratory scales to change, so the temperature around analytical scales must be strictly controlled. When the temperature goes up, water may evaporate from the product or the product may get bigger. If the temperature is too low, condensation may form or the product may shrink. All of these will make the reading wrong. Weighing machines shouldn’t be turned off so that the temperature stays the same, and the room temperature shouldn’t change by more than 2 degrees.
  3. Vibrations – Vibrations can come from things like people walking and doors or cabinets banging, but they can also come from more subtle things like refrigerators and ventilation systems. Due to the small size of the samples, these disturbances can cause them to spill or move around, which can make it hard to get samples or spread them around. If these things happen, you may need to re-calibrate your analytical balance, which will take time and cost more.
  4. Chemicals – Changes in the air around volatile samples can cause chemical reactions that change the state of the samples. It’s important to make sure the sample doesn’t change chemically.
  5. Fingerprints: If the size of the sample is very small (less than 0.1 mg), fingerprints may change the results.
  6. Air Currents – You can make air currents by opening and shutting doors, using air conditioning, or turning on ceiling fans. Because analytical balances are so sensitive, this can change the measurements.
  7. User Errors – Lab balances can give wrong results if they are not calibrated correctly or if samples are left out in the open. In order to reduce this risk, labs usually follow strict standard operating procedures.
  8. Humidity– Most labs have humidity levels below 20% and have air conditioning running 24 hours a day. This makes the air dry, which can lead to friction, which in turn can lead to static electricity. When measuring weight, static electricity can cause big mistakes and differences. This can be fixed by lowering the humidity to 40% when the analytical scales are being put in place. The floor should be anti-static, and plastic containers, which can be porous, shouldn’t be used to store the samples.
  9. Magnet: The way the samples are made could cause inaccurate readings when they are weighed. If the sample is magnetic or becomes magnetic, it may attract other things or create a magnetic field that affects the sensor coil of the balance.

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.

Before Cleaning

  1. Always check how clean the area around the scale is to stop contamination from spreading. Keep the area clean and organised.
  2. Before cleaning, disconnect the scale from the power source.
  3. 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.
  4. 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.

During Cleaning

  1. First, you need to turn off the balance display.
  2. Clean the housing for the balance.
  3. 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.
  4. 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.
  5. 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.
  6. 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.
  7. 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.

After Cleaning

  1. Reassemble the balance and return all removed components to their original locations.
  2. Turn on the scales with sufficient warm-up time.
  3. Complete the balance’s level adjustment and calibration.
  4. Perform a weight test and verify the precision.
  5. After cleaning the balance, cover it with a dust cover to prevent dust and moisture from entering the weighing chamber.
  6. 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

Analytical Balances are utilised for numerous purposes, including:

  • Sample preparation
  • Formulation/Recipe Calculation
  • Checkweighing
  • Periodic weighing
  • Pipette testing
  • Animal weighing
  • Differential weighing
  • Analysis/determination of density
  • Piece tallying

Advantages of Analytical Balance

Analytical balances offer innumerable benefits and make laboratory life easier. Among the benefits of Precisa’s analytical balancing are:

  • Extremely reliable degree of precision
  • Simple to use, practical, accurate, and quick to measure the mass of an object.
  • With its user-friendly menu, you will become familiar with it in seconds, allowing you to explore its full potential.
  • Utilizing the integrated non-contact IR-sensors makes it considerably simpler to complete weighing duties. Additionally, it decreases the danger of infection from contacting the device. Thanks to the new load cell and state-of-the-art signal processing, the weighing data are displayed and displayed without a newly created stability indication system in an amazingly quick manner.
  • Self-calibration system (SCS): With Precisa’s revolutionary weight adjustment mechanism, you will always have a scale that is perfectly calibrated, yielding the most precise results.
  • Electronic levelling for enhanced precision: a visual alert displays on the display if the instrument is tilted beyond the internally recorded levelling tolerances. To readjust the levelling, an electronic virtual guided levelling display will be enabled and will teach you on how to properly level your instrument.

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.

External 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

  • 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.

Difference between an Analytical Balance and a Precision Balance

Analytical 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 Balance

  • 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.

Video guide of Analytical Balance

YouTube video

FAQ

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

References

  • Proper Use of Balances. (2022, August 17). California State University Dominguez Hills. https://chem.libretexts.org/@go/page/74518
  • https://www.axis.pl/en/k-analytical-balances-1.html
  • https://www.nextdayscience.com/blog/analytical-balances.htm
  • https://www.sigmaaldrich.com/IN/en/search/analytical-balance?focus=products&page=1&perpage=30&sort=relevance&term=analytical%20balance&type=product_name
  • https://www.precisa.co.uk/product_category/analytical-balances/
  • https://www.labsalescorporation.com/electronic-analytical-balance.html
  • https://www.scalepeople.com/blog/four-types-of-laboratory-balances/
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  • https://www.laboratory-supply.net/blog/difference-between-analytical-balance-and-precision-balance/
  • https://www.chemicool.com/definition/analytical_balance.html
  • https://www.cerritos.edu/chemistry/_includes/docs/Chem_111/Lab/Exp%203%20Laboratory%20Weighing%20Fall%2008.pdf
  • https://scalesu.com/products/analytical-balances/
  • https://www.mt.com/in/en/home/products/Laboratory_Weighing_Solutions/analytical-balances.html
  • https://ussolid.com/blog/how-to-calibrate-analytical-balance/
  • https://microbenotes.com/analytical-balance-principle-parts-types-examples/
  • https://ussolid.com/blog/how-to-properly-use-an-analytical-balance/
  • https://www.precisa.com/blog/what-is-an-analytical-balance/
  • https://www.pharmaguideline.com/2014/11/drift-and-its-importance-in-analytical-balances.html
  • https://www.labmanager.com/laboratory-technology/analytical-balances-and-proper-weighing-practices-1805
  • https://www.grainger.com/know-how/equipment-information/kh-laboratory-balance-scale-types-care-terms
  • https://owlcation.com/stem/A-Quick-Look-at-Mass-Volume-and-Density
  • https://hyprowira.com/en/blog/analytical-balance-sections
  • https://radwag.com/en/analytical-balances,4,101-101
  • https://www.sartorius.com/en/products/weighing/laboratory-balances/analytical-lab-balance
  • https://in.vwr.com/assetsvc/asset/en_IN/id/26952326/contents/manual-top-loading-balances.pdf
  • https://us.ohaus.com/en-US/Products/Balances-Scales/Analytical-Balances
  • https://www.depts.ttu.edu/meatscience/docs/The-Analytical-Balance-7-23-20.pdf
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