Humidity transmitter provides electrical outputs that are proportional to humidity inputs. It measures variables such as relative humidity, absolute humidity, specific humidity, moisture content, dew point, temperature and pressure. Some humidity transmitters measure pressure. Others measure temperature, which maintain constant output readings across a range of temperatures. Those transmitters that use chilled mirrors are cooled to a specific temperature. This is the dew point at which moisture begins to condense on the surface. The neutrons are slowed by the presence of moisture in a material, which is measured in the nuclear humidity transmitter. The features for selecting humidity transmitters include self-calibration, self-testing, diagnostics and data logging. These transmitters differ in terms of display type, electrical outputs and digital outputs. The electrical outputs for humidity transmitters include analog currents, analog voltages, frequencies or pulses and switches or relays. These are used for cleaning operations.