I'm looking for information on hand held psychormeters/hygrometers and am wondering if anyone has had good experiences with particular brands/models. I'm looking for accuracy around +/-.5% RH for lab humidity transmitter validation.
"Validation" in what sense? What is your transmitter accuracy? Your tester ought to be 4x better, but that's assuming you need that level of accuracy to begin with
Simply that, I want a hand held sensor to take to sample points near BMS transmitters to determine the drift/accuracy present. The plant transmitters are 10 years old and to my knowledge have never been calibrated post-base build.
I don't need high levels of accuracy as this not a critical process control HVAC application.
You are probably not going to find +/-0.5% for a handheld. The vaisala unit mentioned above will do +/-1% up until about 90%RH and that is really good.
Most room sensors are good for +/-5% and some better ones do +/-3%, so a +/-1% calibration checker will be fine for your purposes. If you have higher precision sensors, then you need to remove them and calibrate them over a salt bath.
The real value in the handheld is that it can be readily calibrated, which is where you get your confidence in measurement.