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Troubleshooting HMP60 reading incorrect value

thomas.miletich Oct 17, 2022 12:39 PM

One of our weather stations that uses a CR800 datalogger suddenly started reading much lower humidity with it's HMP60 and I've had trouble figuring out why. The wiring didn't change and I even tried replacing the HMP60 but the behavior didn't change. It went from being within a few % RH of the other MET stations to a offset of 30-40% RH and othertimes it looks like the trends vertically mirror what the 'correct' HMP60s from other MET stations read. 

Anyone know a way to troubleshoot this?

JDavis Oct 19, 2022 04:17 PM

Those sensors are a simple voltage output. You can check the readings independently with a multimeter. Leave it connected to the datalogger. Check the humidity signal voltage versus ground. Divide millivolts by 10 to get the humidity.

thomas.miletich Oct 20, 2022 04:11 AM

JDavis, your post really helped and I managed to fix my issue. I probed the voltage and it was making the correct voltage for what the datalogger was reading, made me realize it wasn't an issue with the datalogger but instead the cable. It turns out there was a kink in the RH wire that had started to corrode (thanks to Florida salt / humidity), which increased the resistance of the cable so the RH reading was inaccurate. 

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