Hardness tester · Calibration procedure
Force accuracy
Compares the force shown by the tester with a known applied force from calibrated weights or a reference load cell, across the working range.
PURPOSE
Why this is checked
Hardness limits are used to control compression. If the load cell reads high or low, the press may be set wrongly and batches may fail friability, disintegration or dissolution.
Frequency
Typically every 6 to 12 months, and after repair, as defined in your calibration SOP.
Learn how the Hardness tester worksYOU WILL NEED
Standards & tools
- Calibrated reference load cell / force gauge traceable to national standards
- or certified dead weights with a manufacturer's vertical calibration fixture
BEFORE YOU START
Prerequisites
- Jaws clean
- Instrument warmed up and zeroed with no load
- Calibration fixture fitted as the manufacturer describes
PROCEDURE
Step by step
- 1Zero the tester with no load.
- 2Apply the first reference force (e.g. 20 N) and record the tester reading.
- 3Repeat at points across the range used (e.g. 50, 100, 200 and 300 N).
- 4Calculate the % error at each point.
RECORD
Example observation table
| Reference force (N) | Tester reading (N) | % error |
|---|---|---|
| 20 | 20.1 | +0.50 |
| 50 | 49.7 | −0.60 |
| 100 | 100.6 | +0.60 |
| 200 | 199.2 | −0.40 |
| 300 | 299.0 | −0.33 |
CALCULATION
How to calculate the result
% error = (Reading − Reference) ÷ Reference × 100
- Reference 100 N, reading 100.6 N
- % error = (100.6 − 100) ÷ 100 × 100 = +0.6%
ACCEPTANCE CRITERIA
Pass if
- Typically within ±1% of the reference force (or a fixed tolerance such as ±1 N at low forces), as defined in your SOP.
IF IT FAILS
What to do
- Label the tester out of calibration
- Get the load cell adjusted or replaced
- Assess in-process decisions made since the last pass
In LimsPulse · Calibration Management
LimsPulse schedules this calibration, records the result against limits, and blocks the instrument everywhere if it fails or goes overdue.