Hello,
I am currently troubleshooting a DT800 with multiple analog and digital sensors connected to it to monitor a residence. The analog sensors in question are several thermocouples and a RH sensor.

The issue we have is that the datalogger will report unreasonably high 15 min. data for several of the sensors simultaneously and then go back after an hour or so (sometimes randomly) to reporting normal readings. The digital channels are not affected, however, the analog channels that are affected are not consistent form day to day. This issue does not occur diurnally and seems to only correlate with with higher temperatures.

We did review our grounding for the sensors and have installed only the shielded cable grounds to the chassis ground. We also installed and instrument isolation transformer in between the grid and logger power supply as well as the RH sensor reference power supply.

Any thoughts on this would be greatly appreciated.

Thanks,
Matt

Hi mtseitzler,

Please check the possibility of ground loop and electrical noise.
Given the fact the disturbance is not consistent from day to day, it is possible that there is some electrical devices that create noise nearby.

Best regards,
Rudy Gunawan

Rudy,
Thank you for the reply.

We examined possible ground loops and have verified that during normal operations they do not exist. Keep in mind that these are 15 min. averaged values that are sporadic.

Is there a possibility that the logger itself is having issues?

Thanks,
Matt

Hi mtseitzler,

If that is 15 minutes average value, could you give me a snapshot of the real data?
I.e.: if your reading at 1 minute interval and you averaged 15 values in 15 minutes interval. I like to see 1 minute of data.

The logger has no issue with thermocouple. This type of sensor is quite sensitive, so some care is needed to ensure its working condition.

Best regards,
Rudy