AFA-G Humidity Measuring Instrument

The KOBOLD AFA-G humidity sensors are suited for measuring relative humidity in air and in other non-aggressive gases. 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%. 

Besides providing the output signal of 4 to 20 mA, the measuring instrument allows the measured value to be read off a red LED display at the measuring point. The display is supplied from the 4 to 20 mA signal current and thus requires no additional power supply. 

The measuring instruments are also available with a programmable switching output. Sensors from the range are delivered with an Aluminum sensor unit and a gauze filter. The connection is made with a right-angle plug according to DIN 43650.