When judging whether the viscometer is accurate, we need to consider the errors of the instrument itself and the standard liquid itself. For a certain combination of rotor and rotation speed, the measurement error range of the viscometer is the maximum viscosity value that can be measured under this combination. For standard fluids, the margin of error is (+/-) 1% of the nominal viscosity value.
example:
Calculate the allowable viscosity error range when the RVDV-II+ viscometer rotates at 2RPM and the RV-3 rotor uses the Bolifei viscosity standard solution 12,500 with a viscosity value of 12,257cP at 25°C to verify its accuracy .
1. Calculate the maximum viscosity value that can be measured under the current situation
Maximum viscosity value (cP) = TK*SMC*10,000/RPM
TK is spring torsion equivalent, for RVDV-II+ viscometer is 1.0
SMC is the rotor constant, 10.0 for #3 rotor of RVDV-II+
Maximum viscosity value=1*10*10,000/2=50,000cP
Therefore, the error range of RVDV-II+ viscometer in the current situation is 50,000cP*(+/-)1% = (+/-)500cP
2. Standard liquid viscosity error=12,257*(+/-)1% = (+/-)122.57cP
3. Allowable viscosity error range = viscometer error range + standard liquid viscosity error range
= (500+122.57) = (+/-)622.57cP
4. Therefore when the reading is between 11,634.4 (12257-622.57) and 12,879.6cP (12257+622.57), it proves that the viscometer is working correctly. Otherwise, the viscometer requires inspection and repair.
