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EE181 maximum RH above 100%

Wendy Baxter Nov 12, 2021 09:47 PM

I have a weather station on the coast of California with an EE181 that is programed using CRBasic (pasted in below). After about a month after installation the maximum RH intermittently started going above 100% during periods of high humidity. Does the program need to be modified for a higher threshold than 103? The highest max RH value thus far is 116. Should this sensor be measuring such high max RH values?

'Air Temp & RH (EE181, max output ~1000 mV)
VoltSe (AT_C,1,mV2500,1,0,0,_60Hz,0.1,-40.0)
VoltSe (RH_pct,1,mV2500,2,0,0,_60Hz,0.1,0)
If (RH_pct > 100) AND (RH_pct < 103) Then RH_pct = 100

smile Nov 15, 2021 05:39 AM


it can happen in some weather conditions that in the air there is not only water vapor but water droplets and in this situation almost all humidity probes can return incorrect measurements above 100%. To overcome the problem of storing strange measurements, a SW filter sets all measurements between 100 and a maximum typical of the type of sensitive element to 100. If this value is exceeded, the strange data is archived, highlighting a hypothetical problem, otherwise by reading only 100 you will never know if the probe is faulty.

JDavis Nov 15, 2021 10:06 PM

You may need to rinse salt build up off the sensor with distilled water.

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