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Compressed-air thermometer hygrometer with Ethernet interface and relays

Compressed-air ambient humidity, temperature Ethernet sensor with two relay outputs. T+RH probe from hard anodized duralumin for compressed air up to 25 bars with cable. Humidex reading.

Sensor H3531P is designed for online monitoring of temperature, relative humidity of air without aggressive substances. Three binary inputs to detection of two-states signals are the advantage. Other devices are controlled by two relay outputs.

High precision capacitive polymer sensor ensures excellent long term calibration stability and ultimate accuracy. Measured values are also converted to other humidity interpretation: dew point temperature, absolute humidity, specific humidity, mixing ratio and specific enthalpy.

The device is supplied with T+RH probe with 1m cable. Cable lengths 2m or 4m available optionally.


  • code
  • Warranty
    3 years

Technical data

Measured value

Relative humidity
Counted values (dew point…)
Two-state signal


Measuring range -30 to +105 °C
Accuracy ±0.4 °C
Resolution 0.1 °C


Measuring range 0 to 100 % RH
Accuracy ±2.5 % RH from 5 to 95 % at 23 °C
Resolution 0.1% RH


Measuring range -60 to +80 °C
Accuracy ±1.5°C for dew point temperature +10°C and higher at ambient temperature +25°C
±2.0°C for dew point temperature 0°C at ambient temperature +25°C
±3.0°C for dew point temperature -10°C at ambient temperature +25°C
±6.0°C for dew point temperature -20°C at ambient temperature +25°C
Resolution 0.1 °C


Measuring range up to 25 bars
Air flow velocity up to 25 m/s at a pressure of 1 bar (1m/s at a pressure of 25 bar)


Quantity 2
Maximal voltage 50 V
Maximal current 2 A
Maximal power 60 VA


Quantity 3
Signal for binary inputy dry contact, open collector or two-state voltage signal.
Inputs are not galvanically isolated.
Minimum pulse duration on binary input 500 ms
Voltage across open contact < 3,3 V
Low voltage level 0 to +0,5 V
High voltage level +3,0 to +30 V


Operating temperature -30 to +80 °C
Channels 1x connectable temperature+humidity probe
Acoustic alarm from built-in beeper - switchable
Counted values humidex, dew point, absolute humidity, specific humidity, mixing ratio, specific enthalpy
Output Ethernet
Measuring interval 2 s
Range of humidity sensor temperature compensation all temperature range
Available temperature units degrees Celsius, degrees Fahrenheit
Communication protocol WWW, ModbusTCP, SNMPv1, SOAP, XML
Alarm protocols E-mail (SMTP authentication is supported), SNMP Trap, Syslog
Power 9-30 Vdc
Protection class IP40
Dimensions 136 x 159 x 45 mm; length/diameter of external probe 150/18 mm
External probe cable length 1 meter
Weight approx. 410 g
Warranty 3 years

WebSensor "H" Demo