Precision Balances and Scales

A precision balance or precision lab scale, sometimes referred to as a top loading balance, is a type of precision weighing instrument used in the laboratory as well as in production environments. Precision balances and precision lab scales are used in a wide variety of applications, including simple weighing, dynamic weighing, sample preparation, statistical quality control, formulation and interval weighing, to weigh from just a few grams up to many kilograms. METTLER TOLEDO precision balances offer readabilities from 0-4 decimal places, i.e. from 1 g down to 0.1 mg (0.0001 g), and capacities up to 64 kg. Our high-performance precision balances offer up to 4 decimal place readability (0.0001 g or 0.1 mg), and are ideally suited to applications that involve a heavy tare container and low sample weight or when it is necessary to weigh large and small quantities into the same container.

Precision balances and precision lab scales produce steady readings in a wider range of environmental conditions than analytical balances. This is because the weighing cell of a precision scale or balance is less sensitive to temperature fluctuations and air currents.

While a draft shield is not usually necessary when using a precision balance with 1 or 2 decimal place readability under standard precision weighing conditions, it can help when working in a fume hood because it protects the precision weighing cell from the internal air flow. 1 mg and 0.1 mg precision balances have a highly sensitive weighing cell and are thus more susceptible to air drafts. A draft shield helps to maintain performance. In fact, many 1 mg and 0.1 mg readability precision balances are fitted with a draft shield as standard.

However, METTLER TOLEDO's Excellence level precision balances and precision scales have the innovative SmartPan weighing pan. The SmartPan weighing pan has been cleverly designed to minimize the effects of air currents on the precision weighing cell. This has improved repeatability by up to 86% and also enables you to use 1 mg precision balances without a draft shield under standard weighing conditions. When working in a fume hood or safety cabinet, 5 mg and 10 mg precision balances with the SmartPan weighing pan deliver results up to twice as fast as models without SmartPan.

Read more in our white paper: Outstanding Weighing Performance – Even Under Harsh Conditions.

Precision balances and precision lab scales are widely used in the laboratory and in production for many daily tasks where precision weighing is required including:

• Weighing items and samples
• Sample preparation
• Piece counting
• Statistical quality control
• Formulation
• Sieve analysis
• Differential weighing
• Dynamic weighing
• Interval weighing

Precision balances are used in general laboratories, research and development, and quality control in a wide range of industries, including chemical, pharmaceutical, food, textiles, metals, plastics, and academia. High-capacity precision balances and precision scales with capacities of 10 kg or more are available with a large weighing platform to accommodate larger loads. These high-capacity top loading balances are often used in aggregate, pharmaceutical, chemical, and adhesive formulation applications.

Watch our video to see how METTLER TOLEDO precision balances can simplify your formulation tasks: Formulation Development and Producing Accurate Formulations.

METTLER TOLEDO's precision balances and precision scales work using the principle of electromagnetic force compensation. The weight force of an object placed on the weighing pan of the precision balance is opposed by an electrodynamically generated force. In the stable state, this force is proportional to the applied weight and can therefore be used as a measurement signal. The precision balance interprets the compensating force as weight and displays the result on the balance terminal in the appropriate unit (milligrams, grams, kilograms).

A precision digital scale is an electronic weighing instrument in which the weight measurements are determined via digital/electronic methods. A precision digital scale has a digital display on which weight results are displayed in numbers. This is in contrast to an analog display in which the weight result is read from the position of a pointer in front of a scale. With a digital display, the result is unambiguous, whereas there will always be a degree of subjective reading error when reading the weighing result off an analog display. However, an analog display has the advantage that it is possible to determine weight values that are fractions of the divisions of the weight values. The smallest increment in the weight values on a digital display is known as the scale division, d.

The precision of a digital scale is usually referred to as its readability. This is the smallest difference in weight that can be recorded on the balance and is known as the scale division, d. The smallest difference in weight that can be determined on a precision balance should not be confused with the smallest amount that can be weighed accurately on a precision balance. This is known as the minimum net sample weight.

A precision weighing scale is another name for a precision balance, sometimes also referred to as a precision scale, precision lab scale or top loading balance. 

A high performance precision balance is specially selected for its high performance weighing cell, which offers a higher level of accuracy than a regular precision weighing cell. A high performance precision balance offers high capacity coupled with high readability, making it possible to weigh both light and heavy items accurately. Due to the high readability, a high performance precision balance enables small sample sizes to be weighed in heavy tare containers, for example in gas filling applications. When producing formulations consisting of large sample quantities together with small sample quantities, a high performance precision balance enables you to use just one container for the whole process. High performance precision balances are also used for mass determination by weight calibration service providers. Mass measurement applications involve comparing the mass of an artefact to the known mass of a reference weight, hence a high performance precision balance is often called a comparator balance.

Learn more about our comparator balances.

Take a look at one of our most popular high performance precision balances that is widely used to dispense small sample quantities into heavy tare vessels, for example in gas filling and formulation applications: Comparator XPR26003LC.

Before starting to weigh on your precision balance or precision lab scale:

• Check that calibrations and routine tests are up to date.
• Check that the balance is level.
• If necessary, wear gloves to protect yourself as well as to avoid contaminating your sample. For some samples, personal protection equipment may be required; check your SOP.
   

To weigh a sample on your precision balance or precision lab scale:

1. Zero the balance
   • This gives you a zero point from which to start your weighing process.
2. Place your container centrally on the weighing pan
   • This avoids corner load error.
3. Allow your precision balance to settle.
   • The weight of your tare container will be shown on the display.
4. Press the tare button.
   • Although the display will now show zero (the number of decimal places will depend on the model of precision balance), the balance has recorded the weight of your container. This is not the same as the zero point and to indicate this, the net weight indicator 'N' will also be shown on the display.
5. Add your sample to the container until you reach the target weight.
   • Many METTLER TOLEDO precision balances and precision scales feature a weighing-in guide to help you weigh more precisely within your defined tolerances.
6. When the balance has stabilized, you can record the net weight of your sample.
   • The balance has now recorded the weight of your tare container and the weight of your sample.
7. Print out or transfer your results.
   • The different weights will be shown with T for tare, N for net, and G for gross (total).
8. Clean the balance and the area around the balance according to your SOP.
    

To weigh an item on your precision balance or precision lab scale:

1. Zero your precision balance.
2. Place your item centrally on the weighing pan.
3. The weight value is released once the precision balance has settled.
4. Clean the balance.
    

For more information on all aspects of weighing, download our indispensable weighing guide: Weighing the Right Way.

Using the zero function provides you with a zero point from which you can start weighing. If you already have something on the precision weighing pan, a protective cover for example, the zero function effectively ignores this. The zero function does not include any weight already registered by the weighing cell as part of your weighing process. However, it is important to note that any weight on the precision balance still counts towards the total load you can place on the balance (i.e. the balance capacity).

When you place a container on your precision balance and then press the tare function, the display resets to zero and the balance internally records the weight that is on the weighing pan. The balance is now ready for you to add your sample to your container. When you print out the results, the different weights are recorded with T for tare weight, N for net weight, and G for gross weight (the total weight).

In practice, you should start your weighing process by pressing zero →0←, and record the weight of your container by pressing tare →T←.

Every precision weighing application is different, and the ideal precision balance for laboratory weighing may not be right for a very similar application in a production environment. In the laboratory, a precision balance may have the challenges of drafts, vibrations and fume hoods, whereas on a factory shop floor, for example, there may be dust, dirt, vibrations from machinery, and multiple operators across different shifts.

Precision weighing is often the first step of an analysis or process, so having accurate weighing results is important to avoid errors later. To achieve accurate results that meet your process tolerances, you need to be sure that your balance is fit for purpose. METTLER TOLEDO's free GWP^® Recommendation service helps you choose the right precision balance for laboratory or manufacturing applications by considering several key factors:

• Maximum weight: the maximum amount you want to weigh (including the tare container)
• Smallest net weight: the smallest sample you want to weigh (excluding the tare container)
• Weighing tolerance: the degree of error that is acceptable, specified as a ± percentage
• Safety factor: to compensate for variations due to drafts, different operators, vibrations, etc., the minimum weight is multiplied by a factor that reflects the degree of risk associated with having an incorrect weighing result (i.e., a high negative consequence requires a high safety factor).

Not only does GWP^® Recommendation help you choose the right precision balance for laboratory and production weighing applications, it can help you verify that your existing precision balance is fit for purpose. To learn more, see: How to Select a Laboratory Balance and Scale That Meets Your Requirements.

The smallest net weight that can weighed accurately on your precision balance or precision scale is known as its minimum weight. The minimum weight is different for every precision balance and varies according to the performance of the weighing cell, the ambient conditions, the balance location, and the accuracy you require. Below the minimum weight value, the measurement uncertainty becomes too large and the weighing result cannot be trusted. Many METTLER TOLEDO precision balances incorporate a function known as MinWeigh. When the weight of your sample is below the minimum weight, the figures on the display remain red and the weight value is not released. The minimum weight of each individual precision balance must be determined in its place of operation. METTLER TOLEDO service technicians can determine the minimum weight for you as a key part of the precision balance service.

Learn more from our white paper: GWP^® – The Standard.

The capacity of your precision balance or precision scale defines the maximum load. METTLER TOLEDO precision balances offer capacities from 120 g up to 64 kg and the model name indicates the balance capacity. For example, the capacity of the XPR4002S is 4.1 kg with 2 decimal place readability (0.01 g), and the MS8001TS has 8.2 kg capacity with 1 decimal place readability (0.1 g). The maximum load includes any container and the sample being weighed.

It is important to level your precision balance to ensure your results are accurate. Your precision balance is precisely engineered to operate in the level position so that the load cell registers the full weight force of any item placed on it. If your balance is not level, the weight value recorded will deviate from the true value in proportion to the square of the angle of tilt.

Many precision balances have a level bubble inside a small glass dome, which is usually positioned at the front of the balance, close to the display. Before using the balance, you should quickly check that the bubble is in the center of the dome. If it is not in the middle, use the balance's adjustable feet to adjust the level of the balance and bring the bubble back to the center. Many of METTLER TOLEDO's precision balances and precision scales feature the LevelControl function, which provides a warning if the balance is not level.

On some balance models, on-screen graphical guidance tells you which foot to turn, in which direction and by how much.

Air drafts can certainly influence your precision scale or balance and hence affect your results. Air drafts act on the sample, the container and the weighing pan, exerting an additional force on the precision weighing cell that the balance interprets as weight. Particularly when using a precision balance with a readability of 1 mg, or even 10 mg, this additional weight force can be significant, affecting the accuracy of your results. Lower readability precision balances have a draft shield fitted for this reason.

METTLER TOLEDO's Excellence level precision balances and precision scales are fitted with the SmartPan weighing pan. This unique weighing pan reduces the influence of air drafts on the precision weighing cell, minimizing the associated errors. Thanks to faster settling times, SmartPan makes it possible to deliver results in half the time compared to a standard weighing pan. Under harsh weighing conditions (inside a safety cabinet), results on a 1 mg readability precision balance with SmartPan show an outstanding 86% improvement in repeatability compared to a standard weighing pan. The extraordinary stability provided by SmartPan also enables you to weigh with the draft shield open, minimizing process steps and further helping to speed up operations.  Under normal weighing conditions, a 1 mg readability precision balance with SmartPan can even be used without a draft shield.  

Download our white paper to learn more about SmartPan: Outstanding Weighing Performance – Even Under Harsh Conditions.

Yes, ambient temperature can influence your precision scale or balance. Temperature changes cause expansion or contraction of the components of the weighing cell, affecting its performance and hence influencing your precision weighing results. If the ambient temperature fluctuates at the place where your precision balance is installed, you may experience poor repeatability. To ensure best performance, your precision scale or balance should be installed in a room where a constant temperature can be maintained. When a precision balance is first connected to the power supply or switched on, a warm-up time of approximately 1-2 hours is recommended. This period allows the precision balance to adjust to the ambient temperature and stabilize its environment. This warm-up should be repeated every time the balance is turned on after a period of inactivity. Ideally, you should leave your precision balance switched on.

Most METTLER TOLEDO precision balances and precision scales are equipped with FACT fully automatic internal adjustment. FACT automatically triggers an adjustment procedure whenever a predefined difference in temperature is exceeded. In this way, the accuracy of the precision balance is maintained automatically, without the need for operator intervention.

It should also be noted that articles, samples or containers to be placed on a precision scale should first be acclimatized to the ambient temperature. Items warmer or cooler than the precision scale itself can induce small air currents which influence the weighing cell due to the temperature differential. Not only can this cause drifting weight values, but items can appear heavier or lighter than they actually are.

A precision balance calibration is an assessment of the balance's performance. Calibration does not involve making any changes to the behavior of the balance. In contrast, a precision balance adjustment is an intervention that changes its behavior. Typically, a precision balance calibration procedure might indicate the need for an adjustment. Calibration should always be carried out by an authorized service technician. As part of the whole calibration service, the technician may make an adjustment and calibrate the balance again to verify its performance.

In between regular calibrations by a technician, you should also routinely test your precision balance using two external weights. These routine tests highlight any deviations from weighing process requirements and detect potential issues early.

METTLER TOLEDO has developed a globally applicable scientific standard for the correct selection, calibration and operation of weighing equipment known as GWP^®, or Good Weighing Practice™. Our GWP^® Verification service provides you with all the information you need concerning calibration frequency and routine testing for your specific process and quality requirements: Weighing Devices - Verifying and Maintaining Accuracy Over Time

XPR precision balances have a range of quality assurance features that work together to help you ensure accurate results and to comply with any applicable regulations.

The StatusLight™ is built into the front of the balance terminal and uses color to let you see at a glance if the balance is ready for weighing to begin. The balance status is recorded against each weighing result to provide additional process security.

The GWP Approved function not only actively monitors the balance status, it also ensures you always weigh within the safe weighing range. The on-screen icon is your reassurance of accurate, reproducible results. GWP Approved needs to be activated by your service technician.

The Tolerance Profiles ensure weighing tasks meet defined quality requirements and regulations. An on-screen warning is given if results are out-of-spec. By using the same profile each time a specific task is carried out, consistency and traceability are assured.

To clean your precision balance or precision scale, you will first select your cleaning agent. The cleaning agent selected will depend on your laboratory or workplace and the risk of exposure to harmful chemicals or active substances. However, the cleaning agent must be able to fully remove any contamination without damaging the balance. As a rule, your precision balance should be cleaned after each use or change of weighing substance, but this can vary according to your industry, application and frequency of use. Check your cleaning SOP for the recommended frequency.

A standard precision balance cleaning procedure follows:

1. Get ready – protect yourself and have your cleaning SOP instructions on hand
2. Disconnect the balance from the power supply
3. Clean the area around the balance
4. Disassemble all removable parts
5. Clean the balance itself
6. Reassemble the balance
7. Ensure the balance is ready for use
    

Full details on how to clean your precision balance, including cleaning methods, cleaning agents, and tips on how to keep your precision balance clean can be found in our free guide: 8 Steps to a Clean Balance. A cleaning SOP is included.

The range of a precision balance or precision scale refers to its weighing range. The weighing range is known as the capacity of the balance and is the maximum amount that can be weighed on the balance.

As the name indicates, overload protection safeguards the weighing cell when objects that are too heavy are placed on the weighing pan or if something is accidentally dropped on it; without this protection, the sensitive weighing cell could be damaged. A warning is provided on your balance display when the balance capacity is exceeded. All METTLER TOLEDO precision balances and precision scales incorporate overload protection. 

In commercial applications that involve the direct selling of products by weight, a Legal for Trade balance is required. You should check the legal requirements of the country and area in which you are manufacturing the products and where they are sold. Most METTLER TOLEDO precision balances are available as Legal for Trade versions. Our Legal for Trade precision balances undergo additional testing. We can supply precision balances verified as Legal for Trade (/M models). However, your local regulations may require that the verification is done by weights and measurement inspectors or authorized service technicians in your area (/A models). Local regulations should always be checked prior to making a purchase.

The Legal for Trade seal gives your customers confidence that the balance mechanism has not be tampered with and the weighing results are true.

Lean more: Legal-For-Trade Scales - Weighing on Trade Approved Balances.

Our portfolio of precision balances and precision scales includes several large platform balances. The larger weighing pan enables large loads and bulky items to be weighed with ease. Our large platform precision balances offer capacities from 10 kg up to 64 kg and 0, 1 and 2 decimal place readabilities (1 g, 0.1 g and 0.01 g). Our high-performance precision balances offer 3 decimal place (0.001 g) readability. The choice of capacity and readability will depend on your individual application.

Take advantage of our free GWP^®Recommendation service to ensure you select the right precision balance for your needs: How to Select a Laboratory Balance and Scale That Meets Your Requirements

METTLER TOLEDO precision balances enable an optional hook to be installed on the base of the balance that enables you to weigh large items by suspending them below the balance. The hook can also be used as part of a customized density determination apparatus. This setup is ideal for determining the density of bulky and awkwardly shaped items.

Wearing gloves while weighing not only protects you from harmful substances, but it also helps to prevent cross contamination of your samples. All METTLER TOLEDO precision balances and precision scales are operable while wearing gloves. Our Advanced and Standard level precision balances feature a dedicated glove mode that optimizes the touchscreen for the wearing of reusable (rubber, neoprene) and disposable (nitrile, latex or vinyl) gloves. To learn more, see: Weighing with latex, silicon gloves. Balances with glove mode for disposable and non disposable gloves

The minimum weight of your precision balance is the accuracy limit of the instrument and is the smallest amount that the balance can weigh accurately. It is not the same as the scale division, d; this is the balance readability, which is the smallest difference in weight that can be determined. The minimum weight is not the same for every precision balance and depends on its location, the performance of the weighing cell, the ambient conditions and the required weighing accuracy. Below the determined minimum weight value, the measurement uncertainty becomes larger than the required accuracy and so weighing results cannot be trusted.

To avoid this problem, many METTLER TOLEDO precision balances have a function known as MinWeigh. MinWeigh monitors the weight of the sample being added to the balance. When the sample weight is below the minimum weight, the value is displayed with red digits and the weight is not released. MinWeigh must be set up by a certified technician.

METTLER TOLEDO precision scales & balances can support you with simple data transfer without the need for additional software. Your precision balance must first be connected to your PC, either through the RS232 or USB connections.

• With Advanced and Standard level precision balances, you need to activate PC Direct. Simply press 'Print' to transfer your weighing result to an Excel spreadsheet or Word document.
• With Excellence level precision balances, you need to activate the HID (drop-to-cursor) function. After weighing your sample, press 'Add result' on the balance display and your result will be transferred directly to an Excel spreadsheet or Word document.

For more advanced data management possibilities, we can offer you dedicated software:

• Our EasyDirect™ software provides extended result management capabilities for our Advanced and Standard level precision balances, including csv file exporting, statistical calculations, and review of results.
• LabX^® laboratory software offers advanced data management and results analysis for our Excellence level precision balances. LabX is a highly flexible solution for the centralized management of data, tasks, instruments and users, and can assist you with compliance with 21 CFR part 11 and ALCOA+ data integrity requirements.

Calibration is an assessment of balance performance. Whether you need to calibrate your precision balance or not will depend on where it is being used and whether there are any applicable regulations. In certain regulated environments, calibration is a necessity to verify that the balance is performing as required. Balance calibration is carried out by authorized service technicians, whereas routine testing is done by the balance user. Routine testing is important as it helps to highlight deviations in balance performance that can lead to out-of-tolerance results. Read more on balance calibration.

A precision balance or precision scale typically offers readability from 0-3 decimal places (1 g to 1 mg) whereas an analytical balance is defined as having readability of 4 decimal places or more (0.1 mg).

METTLER TOLEDO offers many precision balances and precision scales that can be broadly categorized as shown below:

1. Large platform
   
   • Precision balance with a large weighing platform to accommodate heavy and bulky loads.
   • Readability: 1 g – 1 mg
   • Decimal places: 0-3
   • Capacity range: 10.1 kg – 64.1 kg
   • Weighing pan: Rectangular pan SmartPan (large)
2. Small platform
   
   • Precision balance with a small weighing platform to accommodate standard loads and less bulky items.
   • Readability: 1 g – 1 mg
   • Decimal places: 0-3
   • Capacity range: 310 g – 10.1 kg
   • Weighing pan: Rectangular pan SmartPan
3. High-performance, large platform
   • Comparator precision balances, carefully selected for their exceptional repeatability at higher capacities.
   • Readability: 1 mg
   • Decimal places: 3
   • Capacity range: 26.1 kg – 64.1 kg
   • Weighing pan: LevelMatic weighing pan (large)
4. High-performance, small platform (supplied with a draft shield) 
   • Comparator precision balances, carefully selected for their exceptional repeatability at higher capacities.
   • Readability: 0.1 mg
   • Decimal places: 3-4
   • Capacity range: 2.3 kg – 10.1 kg
   • Weighing pan: LevelMatic weighing pan (small)
5. With a draft shield
   • Precision balances with a higher readability for weighing smaller loads.
   • Readability: 1 mg – 0.1 mg
   • Decimal places: 3-4
   • Capacity range: 101 g – 5.1 kg
   • Weighing pan: Circular pan Square pan SmartPan (small)
6. Portable
   • Lightweight precision balances, easily moved to wherever you need to weigh and can be battery operated.
   • Readability: 100 mg – 10 mg
   • Decimal places: 1-2
   • Capacity range: 220 g – 6.2 kg
   • Weighing pan: Circular pan