Review on 🌡 WH8040 1%~99% RH HM-40 Type Digital Air Humidity Control Controller 110V by Larry Sabey

This little device seems to work very well. It's smaller than I imagined. It does exactly what it says on the tin and can be set to allow you to set a specific relative humidity level as well as the range it can fall (or rise) to before the relay kicks in. This will prevent the relay from tripping every few seconds. It also has a delay feature that does the same thing I suspect, but I haven't tried it. It seems accurate, maybe 3 or 4% below my cheap digital hygrometer, but it can be calibrated to +-5%. It can be set to humidify or dehumidify. The only difficulty is connecting it; You will need a 110V power cord connected to the rear screw terminals to power it. To connect the device, it is best to make a small case and place a socket and a humidistat in it, connect the white wire and the green wire of the extension cord to the socket, and the black wire to one side of the relay terminal. Then the other side of the relay to the socket. Basically you leave the white wire and green wire intact, but cut the black wire and connect it to a switch on the device so that it turns off when the switch is at rest. Attics/basements too.