Laboratory Balances & Scales, Lab Weighing METTLER TOLEDO
Laboratory Balances and Scales - choose best laboratory scale

Laboratory Weighing

Balances and Scales for the Laboratory

 

Laboratory Weighing – Laboratory Balances and Scales

What is the difference between mass and weight?

The words ‘mass’ and ‘weight’ are frequently used interchangeably, and both are determined by w...

What is the difference between mass and weight?

The words ‘mass’ and ‘weight’ are frequently used interchangeably, and both are determined by weighing, however, in terms of laboratory balances and scales, the difference between the two is key. Mass measures the amount of material in any given item, is independent of location, and remains the same, no matter their environment.

Mass is measured via comparison using a laboratory scale and balance. The kilogram is the SI unit of mass; it is equal to the ‘International Prototype Kilogram’ (IPK), the original object from which the measurement derived.

An object’s weight is how hard gravity is pulling on the mass, as a force. The SI unit for weight is the Newton (= 1 kg x m/s2). An object with a mass of 1.0 kg weighs approximately 9.81 Newtons on the surface of the earth (mass multiplied by earth’s gravity). The weight of an object on a mountain will be less than at sea level, due to gravitational variations - a high accuracy balance or laboratory scale will detect such differences.

The redefinition of the kilogram is scheduled for 2018. Supporting Redefinition of the Kilogram offers further reading about the change.

Although mass and weight are different entities, the process of determining both weight and mass is called weighing.

 

How do electronic balances work? What is the electromagnetic force compensation principle?

With mechanical balances, a sample is placed on one end of the beam, reference weights on the other, until it is perfectly balanced, the sum value of the weights representing the mass of the sample.

Electronic precision balances, analytical balances, and microbalances in high accuracy classes work with a sensor based on electromagnetic force compensation. A coil on a free movable beam is inserted in a permanent magnetic field. An optical electronic sensor current maintains its position, controlled to an accuracy greater than one thousandth of a millimetre. The sensor records vertical position changes when the pan is loaded which is used to change the current in the coil to return to its initial position. The more weight is added to the pan, the more current is needed to compensate it, this is digitized on the display.

 

Laboratory balances and readabilities

Common laboratory balances and scales types are ultra-micro, micro, semi-micro, analytical, and precision balances.

The readability of a balance is the smallest difference between two measured values that can be read on the display. With a digital display this is the smallest numerical increment, also called the scale interval. The readability of a balance is not equivalent to its weighing accuracy.

Several properties may limit performance. The most important are repeatability (RP), eccentricity (EC), nonlinearity (NL) and sensitivity (SE).

Our Laboratory Balances and Scales video course Basics and Weighing Influences explains basic concepts of good weighing practice.

 

How to select the right laboratory balance or laboratory scale?

For accurate measuring, consider:

  • Required weighing accuracy -> sets the upper limit to the allowable measurement uncertainty of the balance to ensure process tolerances e.g. 1%
  • Safety Factor -> ensures that even with changes over time, the required weighing accuracy is still kept
  • Required smallest net weight to be weighed -> specifies the minimum weight the laboratory scale must achieve (according to measurement uncertainty and/or customer process tolerances)
  • Largest weight to be weighed (including tare) -> specifies the capacity of the lab scale
  • Environmental conditions and weighing application -> specifies further properties of the laboratory balances and scales

Make sure that you select a lab balance or laboratory scale that meets YOUR process requirements and respective tolerances.

Good Weighing Practice™ (GWP®) is a universal approach to selecting and testing weighing instruments. A global standard, it can be used in any industrial and working area for new or existing weighing systems. GWP® provides documented evidence for reproducible weighing results in accordance with all current quality standards.

Offering reliable product quality and regulatory compliance, GWP® is a benchmark for laboratory balances and scales, and uses two key issues to determine quality:

  • The weighing capacity must be larger than the largest gross load expected to be weighed by the user
  • The minimum weight of the weighing instrument for the accuracy required - including the safety factor - must be smaller than the smallest sample expected to be weighed by the user.

 

What is the resolution of a laboratory weighing instrument?

The resolution is the degree to which change can be detected, usually expressed as a number of points. It is the capacity (in g) divided by the readability (in g).

An analytical balance or scale with a capacity of 200 g and a readability of 0.00001 g has a resolution of 20 million points. METTLER TOLEDO’s highest resolution comparator is the M1 mass comparator, with 1 billion points.

 

Which tolerances are applicable in weighing processes?

Tolerances determine whether a lab balance or lab scale behaves "well enough" to meet process requirements and how much deviation is permittable. Tolerances set the criteria to issue a Pass/Fail statement. Tolerances come from a variety of sources, including legal agencies, manufacturing industries, and the process itself.

  • Legal tolerances:
    Legal tolerances stipulated by OIML R76 or NIST Handbook 44 (US only) assess legal for trade requirements. These tolerances are quite large and easily met with laboratory balances, or when weighing at the lower end of the measurement range.
  • Manufacturer tolerances:
    Manufacturer tolerances ensure that equipment meets manufacturer specifications. Manufacturer tolerances do not consider user specific process requirements, and are unsuitable for improving the weighing process.
  • Process tolerances:
    Specific process tolerances defined by the user, support process improvements and savings on material, waste and rework. For laboratory scales in a legal for trade application, process tolerances should be applied in addition to legal tolerances. For more details on METTLER TOLEDO's GWP Verification® visit: Good Weighing Practice.

    Legal tolerances protect consumers but do not consider specific producer requirements. Optimising process tolerances can have a large impact on process profitability.

 
Analytical balances - Laboratory balances

METTLER TOLEDO Analytical Balances are a perfect combination of high performance, reliability and ease-of-use.

Mettler-Toledo Precision Balances

METTLER TOLEDO Precision Balances are made for reliable and high-precision weighing. Both in the lab and under harsh industrial conditions.

Microbalance and Ultra Micro Balances

Exceeding the limits of weighing: Excellence Microbalance and Ultra Micro Balances display unsurpassed accuracy even with the smallest of samples.

Automated Powder and Liquid Dosing

Automated dispensing of 1 mg to 5 g of free-flowing powders with liquid dispense option to make dosing easier and safer.

Good Weighing Practice™ (GWP®)

GWP® is a global weighing standard that can be applied to new or existing weighing equipment from any manufacturer in any industry and workplace.

Moisture Analyzer

The METTLER TOLEDO family of moisture analyzers provides fast, precise and reliable moisture determination.

Special & Segment Solutions for weighing

Gold and Carat Balances, Stent- and Filter Weighing Solutions, Calibration Solutions for Micro-, Single- and Multichannel Pipettes - we offer a broad portfolio tailored to your special needs.

Mass Comparators

Mass Comparators set the standard in mass metrology and ensure traceability to the international prototype.

Test Weights for Scales

Select weights to test your balance with a wide range from 50 µg to 5000 kg, and optimize your calibration processes with smart accessories.

Applications

Applications for Weighing in the Laboratory

Publications

Services

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Software & Accessories

Accessories

Printer
Weight Handling Accessories
Dosing Accessories
Density determination

Printer and Printer Accessories

Weight Accessories

Dosing Accessories

Density Determination

High quality printers and label printers with dot matrix or inkless thermal transfer technologies for better data management, less transcription errors and faster processes.
Comprehensive range of accessories for professional weight handling.
Automated powder and liquid dispensing for increased user safety, time and cost saving and error reduction.
Density kits and accessories for easy and accurate density determination of solid, liquid and porous substances on precision or analytical balances
Sample Handling
Antistatic Solutions
Filter Weighing Accessories
Pipette Check

Sample Handling

Anti-static Solutions

Filter Weighing Accessories

Pipette Check

Accessories for convenient, error-free and safe sample preparation and transfer.
Single anti-static components and integrated solutions for detection and elimination of electrostatic charges from samples and vessels.
Filter weighing solutions for gravimetric determination of particulate matter (PM) in exhaust and evaporative emissions.
Pipette check kits and evaporation traps to ensure flawless functioning of your pipettes.
Moisture analyzer accessories
Weighing pans and draft shields
Weighing Tables
Instrument protection

Moisture Analyzer Accessories

Weighing Pans and Draft Shields

Weighing Tables

Instrument protection

Complete range of accessories and consumables for Moisture Analyzers required for accurate and repeatable moisture content determination.
Draft shields, pans, weighing pans, carat pans and magnetic protection shields for better weighing performance and more reliable results.
Height adjustable weighing tables provide a stable weighing surface and ergonomic working area, for all kinds of laboratory balances.
Variety of covers and transport cases protect your balance from dirt and damage and anti-theft devices provide maximum security of your instrument.
Hands-free Accessories, Stands & Displays & Data Readers
Filling Process Control
Interfaces, Cables and Power Supplies
Software for Balances

Hands-free Accessories, Stands & Displays & Data Readers

Automatic Small Items Feeding

Interfaces, Cables and Power Supplies

Software for Balances

Wide array of peripherals for improved ergonomics and easy data management, including barcode scanners, RFID readers, optical sensors and displays.
Automatic feeding system for capsules, tablets or small electronic and mechanical components directly into a balance.
Interfaces, Cables and Power Supplies for your laboratory instruments.
Software solutions for error-free data management, calibration with mass comparators and pipette calibration, as well as for a range of weighing applications.
Printer

High quality printers and label printers with dot matrix or inkless thermal transfer technologies for better data management, less transcription errors and faster processes.

Weight Handling Accessories

Comprehensive range of accessories for professional weight handling.

Dosing Accessories

Automated powder and liquid dispensing for increased user safety, time and cost saving and error reduction.

Density determination

Density kits and accessories for easy and accurate density determination of solid, liquid and porous substances on precision or analytical balances

Sample Handling

Accessories for convenient, error-free and safe sample preparation and transfer.

Antistatic Solutions

Single anti-static components and integrated solutions for detection and elimination of electrostatic charges from samples and vessels.

Filter Weighing Accessories

Filter weighing solutions for gravimetric determination of particulate matter (PM) in exhaust and evaporative emissions.

Pipette Check

Pipette check kits and evaporation traps to ensure flawless functioning of your pipettes.

Moisture analyzer accessories

Complete range of accessories and consumables for Moisture Analyzers required for accurate and repeatable moisture content determination.

Weighing pans and draft shields

Draft shields, pans, weighing pans, carat pans and magnetic protection shields for better weighing performance and more reliable results.

Weighing Tables

Height adjustable weighing tables provide a stable weighing surface and ergonomic working area, for all kinds of laboratory balances.

Instrument protection

Variety of covers and transport cases protect your balance from dirt and damage and anti-theft devices provide maximum security of your instrument.

Hands-free Accessories, Stands & Displays & Data Readers

Wide array of peripherals for improved ergonomics and easy data management, including barcode scanners, RFID readers, optical sensors and displays.

Filling Process Control

Automatic feeding system for capsules, tablets or small electronic and mechanical components directly into a balance.

Interfaces, Cables and Power Supplies

Interfaces, Cables and Power Supplies for your laboratory instruments.

Software for Balances

Software solutions for error-free data management, calibration with mass comparators and pipette calibration, as well as for a range of weighing applications.

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