When sequencing two sample streams, why does the APA6000 analyser shut down (go into standby mode) if only one sample stream is lost?

Document ID

Document ID TE6720

Published Date

Published Date 21/01/2019
Question
When sequencing two sample streams, why does the APA6000 analyser shut down (go into standby mode) if only one sample stream is lost?
Summary
Dual stream APA6000 analyser in standby mode when one sample stream is lost.
Answer

Any time a sample is lost, the analyser will continue monitoring the stream for at least 45 minutes to make sure it doesn’t have sample. This will take care of temporary losses of sample. If the sample is not restored within this period of time the analyser will finally shut down (go into standby mode). This was decided because Hach did not want the APA6000 to continue to run when sample is not present. First of all, if the analyser is completely out of sample and has internally dried up, we do not want the pump to continue to run (even periodically) and destroy the pump seals. The second reason is that the APA6000 will not give correct reading when it has air within the internal fluid system (tubing or pump). If the analyser would periodically try to aspirate sample from a port which has no sample, it may require an hour or more before the air is fully purged and the analyser can start giving reliable readings. The lack of flow from one sample stream will likely affect the readings of the other sample stream due to the air in the tubing and pump.