Review on 🌡️ Extech RH390: Superior Precision Dual Display Hygro Thermometer Psychrometer by Jamal Sandridge

For calibrating room thermostats. Assuming it's accurate, it works as it should. The meter and most thermostats range from 2 to 4 degrees and 4 to 6 percentage points relative humidity, so this is useful for calibration. The reason for the 3 star rating is that all 4 screws connecting the front and back covers were missing. This quality control issue makes me doubt the rest of the device. I discovered this by accident. I unscrewed the battery cover and didn't unscrew the screw all the way. I pulled the battery cover and the back cover detached. I taped it around but was disappointed for a $200 device. Thanks to those who mentioned the dust cap issue. I removed it very carefully and had no problems.