I recently read a probe (New Wagner Orange Reader) and got a reading of 89% at 69°. I immediately read the test again and got a reading of 86% at 71°. I read it a third time at 83% at 72°.
Can I assume the first reading is correct? My assumption is when taking multiple readings the electrical current running thru the sensor is causing it to heat up and reducing the RH in the hole. Is this correct?
How long was the sensor in the hole?
After the required 72 hours, the first reading will be the most accurate. I have noticed a small amount of drift as the reader transfers its thermal energy to the sensor, and this drift selfs corrects as equilibrium is regained. I know this issue was being worked on, and I am unsure if the orange readers have eliminated this phenomenon.
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Either way your still to high for moisture sensitive floorcovering materials.
Also is your reader acclimated or are you bringing it in from a warm or colder place then reading it?
Thanks CC and Ernesto! The sensor was in the hole for 73 hours and the reader was well acclimated.
We noticed this with the old blue system also. The blue reader would initially read 93% and slowly tick down to may be 86%. After setting several hundred of the blue sensors we moved away from the Wagner's to another system with removable sensors. We want to go back to the Wagner system for many reasons. Removable sensors need to be checked for calibration (hassle) and the time it takes to acclimate removable sensors is not acceptable for large jobs with 40 to 100 RH tests.
I am the kind of guy that needs to understand what is happening to have full confidence.
You are right, the first reading is the one you want.
Often, the Reader itself (old blue or new orange) is warmer - sometimes, much warmer - than the internal slab temperature being sensed by the Smart Sensor barrel. This is a normal phenomena for any electrical unit. As CC mentioned, this heat can transfer via the metallic contacts on the bottom of the Reader through the metallic traces on the bottom-inside of the Smart Sensor.
CC also stated to just get the very first reading with the old blue Reader. The old blue Reader would actually re-scan the sensor each scan cycle. This was unnecessary because we only need to see the very first reading anyway so we educated people to just get the very first reading of the 30 second ON time when they were using the old blue Reader.
With the new orange Easy Reader, you just put the reader in, and when it comes on, immediately take it out (it will conveniently stay on for up to 5 minutes) and log your readings, and then go to the next Smart Sensor. There is no need to keep trying to get readings from the same sensor within the same minute or two for the reasons stated above. The first readings are what you want, and are the accurate ones.
Feel free to write back contact me if you have additional questions,
It now makes sense. Although the reader was acclimated to the ambient air temperature the slab temperature was much lower.