What can cause an 'unstable reading' message on the 5500 sc analysers?

Document ID

Document ID TE9640

Published Date

Published Date 21/01/2019
Question
What can cause an 'unstable reading' message on the 5500 sc analysers?
Summary
'Unstable Reading' on 5500 sc analysers
Answer
The 'Unstable Reading' message on the 5500 sc analysers indicates that the analyser sees too much variability in the reference or color reading when measuring a sample. The analyser will measure both the reference and color sample 12 times during each sample measurement and then will disregard the three highest and three lowest measurements. The remaining six measurements are then averaged together and if a high standard deviation (greater than 1.5%) is seen by the analyser, you will get the 'Unstable Reading' measurement.

When the 'Unstable Reading' message is seen, the analyser is not indicating that there is instability from reading to reading, but instead instability in a single reading. Issues such as bubbles moving throughout the sample, high turbidity, and the sample cell not being completely flushed can cause this message because the analyser is not seeing a consistent intensity of light when it takes each set of 12 measurements.