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Fieldpiece Digital Psychrometer Accessory Head - ARH4

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Fieldpiece Digital Psychrometer Accessory Head - ARH4


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Fieldpiece Digital Psychrometer Accessory Head - ARH4

Fieldpiece Digital Psychrometer Accessory Head - ARH4



ARH4 Digital Psychrometer Accessory Head by Fieldpiece

The Fieldpiece ARH4 Digital Psychrometer Accessory Head measures both relative humidity and ambient air temperature. It calculates dew point and wet bulb. It's great for calculating target superheat as well as logging %RH, temp, WB or DP over time. The head converts %RH, ambient temperature, dew point temperature, and wet bulb temperature to a voltage at a rate of 1 %RH or degree to 1mVDC and your reading is displayed on your meter. The ARH4 snaps directly onto Fieldpiece stick meters, data logger, electronic handles and adapters.

The ARH4 employs an advanced pair of sensors, a thermistor and a hygrometer, that sense temperature and moisture in the air. With built-in psychometric charts, the ARH4 calculates dew point and wert bulb based on these direct measurements. For the most accurate readings, expose the ARH4 to the air you are measuring for a few minutes so that the sensors can come to equilibrium.

  • Measures temperature and relative humidity percentage
  • Calculates wet bulb and dew point temperatures
  • Log relative humidity over time to help troubleshoot systems


  • Digital Psychrometer and Hygrometer Accessory - ARH4
  • 9V Battery (installed)
  • Operator's Manual
General Specifications
Low battery indication Red LED is lit when the voltage drops below the operating level.
Output impedance 500Ω approx
Operating environment 32°F to 120°F (0 °C to 50 °C) at <95%RH
Storage temperature -4°F to 140°F (-20°C to 60°C) <80%RH with battery removed
Accuracy Stated accuracy at 73°F±10°F (23°±5°C), <95%RH
Battery 9V
Dimensions 146mm(H) x 67mm(W) x 32mm(D)
Weight prox. 180g including battery
Sensor thermister temperature sensor
Range -4°F to 140°F (-20°C to 60°C)
Resolution 0.1°C / 0.1°F
Accuracy ±1°F 32°F to 113°F
±2°F -4°F to 32°F,
113°F to 140°F
±0.5°C0°C to 45°C
±1°C -20°C to 0°C,
45°C to 60°C
Output 1mV/°C,1mv/°F
Relative Humidity
Sensor Capacitive humidity sensor
Range 0% to 100%RH
Accuracy ±2.5%@77°F(25°C), 10% to 90% RH
±5%@77°F(25°C), <10%RH, >90%RH
Output 1mV/%RH
Sensor response time 60 seconds typical for 90% of total range
Sensor hysteresis (excursion of 10% to 90% to 10% RH) ±1%RH typical

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