AFA-G Humidity Measuring Instrument

Brand: KOBOLD Instruments, Inc.

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.



  • ± 2 % Relative Humidity (For Range 5 to 95 % Relative Humidity & 10° to 40° C)

Ambient Temperature Range

  • -40° to 80° C (-40° to 176° F)


  • Bakery Technology
  • Greenhouses
  • Monitoring & Control of Air Conditioning Systems, Drying Plant, Humidifiers & Dehumidifiers
  • Research & Development
  • Ripening Warehouses for Food


  • Red LED Display

Electrical Connectors

  • DIN 43650

Environmental Protection

  • IP30
  • IP65


  • 0 to 100 % Relative Humidity - Measuring Range

Measuring Error

  • < 0.1 %/K


  • Duct Mount


  • 4-20 mA - Analog Output

Output Load

  • 650 ohms at 24 Vdc - Maximum

Power Requirement

  • 12-30 Vdc

Response Time

  • < 20 seconds

Sensor / Probe Material

  • Aluminum

Storage Temperature

  • -40° to 80° C (-40° to 176° F)

Switch Type

  • Transistor - Limit Contact Optional (Open Collector)

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