HMT338 Dewpoint and Temperature Transmitter for Refrigerant Dryers with 10 m cable - Vaisala Online Store

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HMT338 Dewpoint and Temperature Transmitter for Refrigerant Dryers with 10 m cable

The HMT338 is a top-of-the-line transmitter especially suitable for compressed air refrigerant dryer monitoring. The Vaisala HUMICAP® Humidity and Temperature Transmitter HMT330 series incorporates Vaisala’s 40 years of experience in industrial humidity measurement.The instrument offers a wide variety of different psychrometric units, including dew point (default), relative humidity, enthalpy, wet bulb temperature, absolute humidity, and mixing ratio.

With the optional ball valve, the HMT338 is ideal for pressurized processes where the probe needs to be inserted or removed while the process is running. The probe depth is adjustable.The HMT338 is optimized for dewpoints down to -10°C (+14°F). For drier (low dew point) measurements, such as in dessicant dryer systems, the Vaisala DRYCAP® Dewpoint and Temperature Transmitter DMT348 is recommended.

See other HMT330-series transmitters

The transmitter has a keypad and a large graphical display for convenient monitoring of the reading and transmitter setting changes. For example both output signal type (voltage or current) and scaling can easily be changed by the user.

Vaisala offers a 10-year warranty for new HMT338 transmitters that are calibrated annually at a Vaisala Service Center. Please see the details on our web page and the conditions of the 10-year warranty.

Analog outputs are preset at the factory to:

  • Channel 1: 4…20 mA = -20...+100°C (-4...+212°F) dew point
  • Channel 2: 4...20 mA = -40...+180°C (-40...+356°F) T

The package includes:

  • Pressure tight probe with 10 m (33 ft) cable
  • Calibration certificate (ISO9001 compliant, traceable to NIST)
  • ISO1/2" and NPT1/2" pressure fittings for probe installation into pipeline or pressurevessel
  • M20x1.5 cable gland and NPT1/2" conduit fitting included to facilitate wiring
  • User's Guide in English

HMT338 Dewpoint and Temperature Transmitter for Refrigerant Dryers with 10 m cable
HMT330 series: HMT338 Dewpoint and Temperature Transmitter for Refrigerant Dryers, ball valve is an optional accessory
Standard delivery time for single unit: 1 week
About delivery times »
Warranty: 24 months, extended to 10 years if calibrated annually at a Vaisala service center
About warranty »
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Detailed information

Measurement parameter(s)Dew point temperature
Relative humidity
Absolute humidity
Mixing ratio
Water vapor pressure
Wet bulb
Measurement range0 ... 100 % RH
-70 ... +180 °C (-94 ... +356 °F) T
Measurement accuracy±1.0 % RH (0 ... 90 % RH)
±1.7 % RH (90 ... 100 % RH)
±0.2 °C (±0.36 °F) T
Operating temperature-70 ... +180 °C (-94 ... +356 °F)
High temperature+180 °C (+356 °F)
Operating pressure0 ... 40 bar (0 ... 580 psi)
Operating voltage10 ... 35 VDC, 24 VAC ±20%
Analog outputs4 ... 20 mA (default setting)
0 ... 20 mA
0 ... 1 V
0 ... 5 V
0 ... 10 V
Digital outputsRS-232
Housing classificationIP65 (NEMA 4)
Links See full specifications on
Download user guides and other product documents on

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