FAQ: Why does my instrument Pass and Fail on the same Diagnostic Test Value? Our customer has an issue with the repeatability test with their UltraScan PRO with EasyMatch QC-ER ver. 4.51. The problem is that sometimes the test fails (for just a single measurement).
As you know, our client is an international pharma company and for their rules/procedures, before to measure their samples, they need to run the diagnostic repeatability and the green tile test.
If a test fails, they can re-launch it only another time.
If it fails again, the user has to stop their tests and call the supplier (us).
In the Repeatability Test it failed only for a single reading (11) of the 20 even if the difference measured is dE* = 0.03.
The customer would like to know why some readings with a dE* of 0,03 pass and why other ones fail even if on the specification of the UltraScan PRO the tolerance for this test is dE*< or equal to 0.03 (they expect to get a 0.04 in order to fail the test). They noticed this behavior in the last 1-2 months and more or less the 50% of the repeatability tests fail.
Answer:
In the Short Term Repeatability Test, the PASS/FAIL tolerance is a very tight dE* <= 0.03. What you are seeing is behavior that is a PASS or FAIL in the decimal places beyond 0.03.
- For example, if a reading is 0.028 from the initial baseline reading, it will round off to display 0.03 and PASS the individual reading as being under the tolerance.
- If a reading is 0.032 from the initial baseline reading, it will round off to display 0.03 and FAIL the individual reading as being over the tolerance.
In EasyMatch QC+ER 4.82 TTP1533, to avoid this situation we changed the PASS/FAIL tolerance to a more precise +/- 0.035 so that the test statistics will have to measure higher than 0.035 and display 0.04 to FAIL.
We have also applied this more precise 0.XX5 format to all tolerances in our Diagnostic Tests (Short Term Repeatability on White; Long Term Repeatability on Green; Wavelength Check on Didymium Filter) to deal with this round-off issue.
This display anomaly can be dealt with by upgrading to our latest released version of software.
There may still be an underlying performance issue with the sensor. Aside from the display anomaly, this customer's sensor is moving towards the edge of the PASS/FAIL 0.03 spec for the Repeatability Diagnostic Test. It suggests that this instrument is starting to experience some slight noise in its electronic components that may eventually require service.
Do you still need more information? Submit a ticket and our support team member will reach out to you soon!