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Installation and Configuration Manual 47
General MaintenanceCalibration Check
Chapter 5
Calibration Check
5.1 Calibration
5.1.1 Factory calibration
Prior to leaving the factory, the 7829 Viscomaster
®
/ Viscomaster Dynamic
™
viscosity meter is
calibrated within a standard physical boundary (typically 52.5 mm diameter) against Transfer
Standard instruments traceable to National Standards.
Three fluids ranging in density from 1 to 1000 kg/m
3
are used to establish the general density equation
constants K0, K
1, and K2 (see Section 5.1.5). The temperature coefficients (K18 and K19) are
derived from the air-point and material properties.
The calibration procedure relies on units being immersed in fluids whose density is defined by
Transfer Standards. Great attention is paid to producing temperature equilibrium between the fluid,
the unit under test and the Transfer Standard (see Section 5.1.2). In this way, accurate calibration
coefficients covering the required density range can be produced.
Viscosity calibration is achieved using three fluids (or four for the 0 – 10 cP range) with different
calibrated viscosity values to derive the three general viscosity equation coefficients V0, V1, and V2
(see Section 5.1.4.)
All instruments are over-checked on water to verify the density calibration, and with two different
fluids to check the viscosity calibration. This check is monitored by the Micro Motion Quality
Assurance Department.
5.1.2 Calibration of Transfer Standards
The Transfer Standards for viscosity calibration are fluids which have been accurately measured
within the Micro Motion Standards Laboratory. For density calibration, Transfer Standard
instruments used in the calibration are selected instruments which are calibrated by the British
Calibration Service Calibration Laboratory and are certified.
Transfer Standard calibration uses a number of density-certified liquids, one of which is water. The
densities of these reference liquids are obtained using the Primary Measurement System whereby
glass sinkers of defined volume are weighed in samples of the liquids.
Calibration of the Transfer Standard instruments is performed under closely controlled laboratory
conditions and a calibration certificate is issued. Calibrations are repeated, typically every six
months, producing a well-documented density standard.