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Quality management
Monitoring of measuring instruments

Monitoring of Measuring Instruments

GLP, ISO/IEC 17 025, ISO 9001

Analytical laboratories have to verify and document the accuracy of all measuring instruments used in order to achieve reliable analysis. This especially applies to laboratories operating according to GLP guidelines, DIN EN ISO/IEC 17 025, or certified to DIN EN ISO 9001. The monitoring of measuring instruments requires that the instrument's performance data be known and documented before being


admitted to use and confirmed at appropriate intervals. The frequency of checks depends on the results of previous calibrations. These tests are necessary to ensure continued accu-racy of instruments which may have changed due to aggressive chemicals, or method and frequency of cleaning. Since individual applications are beyond the manufacturer's control, the user should determine the interval of regular tests.


Typical monitoring intervals for liquid handling instruments are every 3-12 months; for glass volumetric instruments, every 1-3 years. Performance certificates issued by BRAND show all instrument data required for monitoring so initial inspection may be eliminated.
Performance certificates are supplied as standard for liquid handling instruments and for BLAUBRAND® volumetric instruments.



The gravimetric test for liquid handling instruments is performed according to ISO 8655; for glass volumetric instruments, ISO 4787 is applied. Traceability of measuring devices to national standards needs to be ensured.


Monitoring of Measuring Instruments in the Lab (German)

Published in Nachrichten aus der Chemie 61, September 2013, GDCh

Cklick here to download


For instruments calibrated to contain (TC, In) the mass of water contained, and for instruments calibrated to deliver (TD, Ex), the mass of water delivered, will be weighed on a balance. The mass of water measured has to be adjusted to account for parameters like water density and air buoyancy on the balance. The thermal coefficient of expansion of glass volumetric instruments has to be taken into account.

Testing scope

While liquid handling instruments are tested individually, the use of statis-tical methods to monitor glass volu-metric instruments is recommended. The following equation to determine the minimum random quantity (a) out of the total quantity (n) has proven effective in actual use:

Random samples have to be taken from each production batch in use.


Testing instructions (SOPs)

To simplify the monitoring of measuring instruments, BRAND offers specific Testing Instructions (SOPs) for every type of volumetric instrument . The testing procedures are outlined step-by-step. At the end of each SOP (Standard Operating Procedure) there is a report to be used for documentation.

Information on volumetric measurement

BRAND provides a booklet on working with volumetric instruments outlining proper use and possible operating errors.

EASYCAL™ Software 

BRAND has developed the EASYCAL™ software that operates under Windows®, to further simplify the monitoring of measuring instruments. Upon entry of instrument data and weighing values, the software per-forms all calculations automatically.
In addition, EASYCAL™ generates electronic and printed test records which can be saved for subsequent use.


Testing Instructions (SOPs), Informa-tion on Volumetric Measurement, and a demo version of EASYCAL™ software can be requested directly from BRAND and are here available for download.