Laboratory balances
Readability from 0.001 mg to 0.1 g, capacity from 1 g to 10.2 kg.
Four families, distinguished by readability and capacity (table below). Two further requirements are checked model by model: the minimum weight according to Ph. Eur. 2.1.7 and CE-M approval, mandatory for sales to the public and for pharmacy compounding.
Magnetic force compensation cell in all families, except the EU-C series (load cell). Models with capacity, readability, linearity and repeatability: see the family pages.
Readability and capacity
Ranges and series by family.
| Family | Readability | Capacity | Series | Weighing cell | Minimum weight |
|---|---|---|---|---|---|
| Microbalances | 0.001 mg | 1 g | Micro 1000 | magnetic force compensation | 0.82 mg |
| Semi-micro balances | 0.01 to 0.1 mg | 100 to 225 g | E50S/3 | magnetic force compensation | 8.2 to 82 mg |
| Analytical balances | 0.1 to 1 mg | 110 to 510 g | CRYSTAL, ETERNITY | magnetic force compensation | 82 to 820 mg |
| Precision balances | 0.001 to 0.1 g | 210 to 10200 g | CENT-2, EU-C, EU-C GOLD | magnetic force compensation (CENT-2); load cell (EU-C) | 0.82 to 82 g |
The weight of the container is included in the capacity. Minimum weight: 820 × d (Ph. Eur. 2.1.7, see below).
Micro, semi-micro, analytical, precision
Uses and main data.
Microanalysis: samples in the milligram range
Quantitative analysis, formulation and process weighing
Ph. Eur. 2.1.7
Minimum weight
The minimum weight above which the measurement uncertainty stays within the required accuracy. It depends on the repeatability of the instrument under its installation conditions.
Chapter 2.1.7 of the European Pharmacopoeia, in force since January 1, 2022, is the reference for balances used for analytical purposes; d is the readability.
View Ph. Eur. 2.1.7Values by readability
| Readability | Minimum weight | Series |
|---|---|---|
| 0.001 mg | 0.82 mg | Micro 1000 |
| 0.01 mg | 8.2 mg | E50S/3 |
| 0.1 mg | 82 mg | CRYSTAL 100-300, ETERNITY 100-300 |
| 1 mg | 820 mg | CRYSTAL 500, ETERNITY 500 |
Cell, adjustment, approval
Cell, adjustment mass and approval at the same readability.
Magnetic force compensation or load cell
CENT-2 and EU-C
The magnetic force compensation cell balances the load with an electromagnetic force and reaches finer readabilities: it is used in the micro, semi-micro and analytical balances and in the CENT-2 series. The EU-C and EU-C GOLD series use a load cell, with a minimum readability of 0.01 g.
- CENT-2: readability down to 0.001 g
- EU-C and EU-C GOLD: readability down to 0.01 g
- Anti-Shock system on both solutions
Internal or external mass
CAL and SMI suffixes
The built-in mass adjusts the instrument without operator intervention: on the ETERNITY series, adjustment starts every three hours or when the temperature changes. Models with an external mass require a certified test weight, in class E or F according to the readability.
- CAL: built-in adjustment mass
- SMI: adjustment with external mass
- Error of the mass below 1/3 of the readability
CE-M approval
CRYSTAL series
Metrological marking is mandatory when weighing affects third parties: direct sales to the public, preparation of prescription medicines, determination of fees or taxes. The CRYSTAL series is approved under Directive 2014/31/EU; the other laboratory series are not.
- Initial verification and renewal every three years (Italian Ministerial Decree 93/2017)
- Metrological operating temperature 18-25 °C
- An approved balance is required for pharmacy compounding
Density of solids and liquids
With the gravimetric method, the balance determines density from two weighings: the sample in air and the sample immersed in the liquid. The density kit adds the hook for hydrostatic weighing, the sample holder, the container for distilled water and the manual lift; the anti-floating pin is used for samples less dense than water.
ISO 1183-1 method: readability of 0.1 mg or finer, sample of at least 1 g (CRYSTAL and ETERNITY series). Other references: OIML G 14, ASTM D 792.
- Below-balance weighing on semi-micro, analytical and CENT-2 balances
- Density of solid, viscous and liquid materials
- Density kit available for the laboratory series
Calibration, adjustment and density
Adjustment: brings the indication of the instrument back to the value of the reference mass; it is performed by the operator or by the instrument itself. Calibration: establishes the deviation with metrological traceability and its uncertainty; it is performed by an accredited center (Calibration reports, LAT Calibration Center).
LAT calibration
Performed by accredited technicians, it provides uncertainty, repeatability and minimum weight. It serves internal checks and external audits, measurements comparable between laboratories (external quality assessment, ring tests), and the detection of worn or stressed instruments.
Adjustment frequency
It depends on three factors:
- product tolerance: the lower it is, the more often adjustment is needed
- number of weighings
- ambient conditions: dust, vibration, drafts, temperature changes
Density of plastics
Density varies with temperature, crystallinity, loss of plasticizers or solvent absorption. For ISO 1183-1: resolution of 0.1 mg or finer and sample of at least 1 g (CRYSTAL and ETERNITY). For samples with density below 1: spherical container or small cage.
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