It is recommended to recalibrate any failed points at least once more. Something external may have caused the calibration failure.
- Temperature related failures:
- There is a difference between the sample temperature and the refractometer temperature.
- Measured temperature is out of the specified +20 … +30 °C (+68 … +86 °F) calibration range.
- The temperature may not be sufficiently stable and is changing. This appears as a long waiting time for stabilization in the RI calibration process.
If the calibration failure is caused by temperature, both refractometer and sample liquid temperature should be allowed to stabilize to be in the calibration range. Retry calibration after a little while.
- Reference liquid related failures:
- There is coating on the prism.
Clean the prism and the sample holder, and then recalibrate.
- There are impurities in the sample
liquid.
Clean the prism and the sample holder. Replace the sample liquid and then recalibrate.
- Reference liquid has expired.
Check the expiration date and use another reference liquid if needed. Notice that the liquids may expire quicker if the containers are left open for extended periods of time.
- There is coating on the prism.