Viscometer · Calibration procedure
Speed accuracy
Measures the actual spindle speed at several settings with a calibrated tachometer and compares it with the set speed.
PURPOSE
Why this is checked
Viscosity is calculated assuming the spindle turns at the set speed. If the real speed is wrong, the shear rate and the viscosity are wrong.
Frequency
Typically every 6 or 12 months and after repair, as defined in your SOP.
Learn how the Viscometer worksYOU WILL NEED
Standards & tools
- Calibrated non-contact (optical) tachometer with traceable certificate, and reflective tape
BEFORE YOU START
Prerequisites
- Instrument level, switched on and warmed up
- Reflective tape fixed to the spindle coupling or a spindle (as the manufacturer allows)
PROCEDURE
Step by step
- 1Set the lowest speed you routinely use, start the motor and let it settle.
- 2Point the tachometer at the reflective tape and record the stable reading.
- 3Repeat at the other speeds you use, for example 6, 30 and 60 rpm.
- 4Calculate the % error at each speed.
RECORD
Example observation table
| Set speed (rpm) | Measured (rpm) | % error | Result |
|---|---|---|---|
| 6 | 5.99 | −0.17% | Pass |
| 30 | 30.02 | +0.07% | Pass |
| 60 | 59.95 | −0.08% | Pass |
CALCULATION
How to calculate the result
% error = (Measured − Set) ÷ Set × 100
- At 6 rpm: (5.99 − 6) ÷ 6 × 100 = −0.17%
- At 60 rpm: (59.95 − 60) ÷ 60 × 100 = −0.08%
ACCEPTANCE CRITERIA
Pass if
- Each speed within the manufacturer's specification or your SOP limit (commonly within ±1% of the set speed).
IF IT FAILS
What to do
- Repeat the measurement, checking the tape and tachometer alignment.
- If it still fails, call service and do not use the instrument.
- Assess results since the last passing check.
MORE
Other Viscometer calibrations
In LimsPulse · Calibration Management
LimsPulse schedules this calibration, records the result against limits, and blocks the instrument everywhere if it fails or goes overdue.