AFH-G Humidity/Temperature Measuring Instrument

Brand: KOBOLD Instruments, Inc.

The KOBOLD type AFH-G measuring instrument serves to measure relative humidity indoors and in air ducts. Auxiliary temperature measurement is available as an option.

The moisture sensing element in the sensor comprises several strips of plastic fabric each with 90 fibres of 3 µm diameter. These plastic fibres undergo a special process to acquire hygroscopic properties, this means that they absorb and release moisture.

The molecular structure of the fibres changes when they absorb water, giving rise to a measurable change in length. The length of the plastic fibres is thus a measure of the relative humidity.

The swelling effect, acting primarily in the longitudinal direction, is sensed by an electronic pick-off system and transferred to an integrated signal preprocessing system. The output signal of the passive sensors is 100 to 138.5 Ω, and 4-20 mA for the active sensors.

The special treatment of the measuring element ensures that its hygroscopic properties remain stable, that is sensitivity is maintained until destroyed by external influence.

Regeneration found in conventional instruments is not required here, but is also not damaging. The measuring element is protected by a perforated tube and is open to the housing.

Measuring instruments with an integrated temperature sensor provide temperature measurement. The temperatures are also converted to the standardized signals 100 to 138.5 ohms and 4-20 mA.

Specifications

Accuracy

  • ± 2.5 % Relative Humidity at > 40 % Relative Humidity
  • ± 3.5 % Relative Humidity at < 40 % Relative Humidity
  • ± 0.5° C (± 0.9° F) - Temperature Measuring Accuracy

Ambient Temperature Range

  • -20° to 60° C (-4° to 140° F) - Housing
  • -40° to 80° C (-40° to 176° F) - Sensor

Applications

  • Building Management Systems
  • Exposed to Dust & Dirt
  • Grain Dryers
  • Greenhouses
  • Monitoring Air Conditioning Systems, Drying Plant
  • R & D
  • Ripening Warehouses for Food

Electrical Connectors

  • Conductor Cross-sections 0.5 mm - Connection Terminals
  • DIN 43760 - Passive Sensors
  • Self-Sealing Grommet M20×1.5 - Cable Connection

Enclosure, Body Material

  • ABS - (Acrylnitril-Butadien-Styrol)

Environmental Protection

  • IP64

Humidity

  • 0 to 100 % Relative Humidity
  • 30 to 100 % Relative Humidity - Operating Range

Insulation Resistance

  • 10 megaohms - Passive Sensors

Linearization

  • < 0.5 % - Linearity Error of Temperature Output: Active Sensor

Load Limit

  • 1 W - Allowed Loading: Passive Sensors

Loop Resistance

  • 100 to 138.5 ohms - Output Linear: Passive Sensors
  • 500 ohms - Active Sensors: Maximum

Media

  • Air
  • Pressureless, Non-Aggressive

Mounting

  • Duct Mounting - Holes in Housing Base
  • Surface Mounting - Brackets (Optional)

Mounting Position

  • Horizontal
  • Vertical - Sensor Pointing Down

Operating Temperature - Sensor

  • -30° to 60° C (-22° to 140° F) - Active Sensors
  • 5° to 80° C (41° to 176° F) - Passive Sensors

Operating Voltages

  • 15-30 Vdc - Active Sensors

Output

  • 4-20 mA - Active Sensors

RFI/EMI Protection

  • EN 50081-2 - Emitted Interference
  • EN 50082-2 - Noise Immunity

Sensor / Probe Material

  • Stainless Steel

Sensor / Probe Type

  • Pt100

Supply Voltage

  • 42 V - Maximum

Temperature Effect

  • -0.1 % Relative Humidity/K -(20° C & 50 % Relative Humidity) -Average Temperature Coefficient

Version / Leadwires

  • 2-Wire

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