Humidity / Temperature Measuring Instrument AFK-G
Capacitive method of measurement
Temperature: 0 ... +200°C
Humidity: 0 ... 100% rH
pmax: 25 bar
Output: 2x 4 - 20 mA
Humidity: ±2 % rH
The range AFK-G humidity/temperature sensors are sensors for measuring relative humidity and temperature (optional) in air and other non-aggressive gases for an operating temperature to 200 °C. The high pressure variant can be used up to a pressure of 25 bar. The sensors are thus ideally suited for measuring humidity in industrial processes. The sensors are based on capacitive metrology which is reasonably-priced, maintenance-free and highly accurate.
Capacitive humidity sensor elements form the basis of these sensors. An electrode system, a moisture-sensitive polymer layer and a gold layer that is permeable to vapour are situated on a small thin glass or ceramic substrate. Since the hygroscopic polymer layer can absorb water molecules that alter its dielectric constant, this layered system acts as a moisture-dependant capacitor, whose capacitance is a measure of the surrounding relative humidity.
The change in capacitance is converted to an electrical output signal by electronics normally mounted on the humidity sensor element. Both parts form a capacitive humidity sensor that can be adjusted using humidity references. Accuracy is approximately ± 2% rH. The transmitters offer a 4 - 20 mA analogue output for relative humidity and a second 4 - 20 mA output for temperature when specified.