HT1800™ Open-path Laser Hygrometer

       In today's uneven distribution of water resources, more understanding of evapotranspiration (ET) can be of great help to water management. Among various techniques, eddy covariance is the most direct method of measuring evapotranspiration. The required eddy covariance measurement system is based on a sonic anemometer and a highly sensitive hygrometer with fast response frequency (e.g. 10Hz).

  • Details

       HealthyPhoton is introducing the new HT1800 TDLAS (Tunable Diode Laser Absorption Spectroscopy) Open-path Hygrometer designed for the eddy covariance method. Since the introduction of the HT8700 Open-path Ammonia Analyzer, we have gradually accumulated experiences in the development and application of instruments in the field of environmental monitoring. Our new HT1800 hygrometer has the open-path configuration that directly measures the moisture content of the atmosphere, ensuring the high accuracy and high speed of measurement. In terms of performance, the instrument fully satisfies the need in the eddy covariance method, and is indispensable in eddy covariance systems for ET analysis and flux corrections of other gas species.

Features and Benefits

Light weight, low cost, easy installation and maintenance

Ideal for eddy covariance and evapotranspiration measurements

Open path configuration, with up to 20Hz measurement frequency

Ultra-sensitive laser spectroscopy brings very low drift

No cross-interference from CO2 and other gas molecules

No moving parts with strong vibration resistance

Robust design for versatile field deployment

Low power (10 W) that can be supplied by a solar panel




 Detection Technology

 TDLAS (Tunable Diode Laser Absorption   Spectroscopy)

 RMS   noise(1σ;  20Hz/10Hz/1Hz)

 7 ppm/ 5 ppm/ 2 ppm

 Measurement Range

 0 - 60 mmol/mol or 0 - 60 pptv

 User Interface

 Windows based software

 Output Data Rate

 20 Hz/10 Hz/ 1Hz user configurable

 Operating Pressure

 70 - 110 kPa

 Operating Temperature

 -20°C ~ 50°C

 Operating Humidity

 0 ~ 100% R.H. Non condensing

 Data Communication


 Data Storage

 On-board storage with SD card or any data loggers with RS-232 communication interface

 Power Requirements

 10 - 30 VDC

 Power Consumption

 Typ. 10 W (max. 30 W at warm up )


 Sensor Head: L450mm×ø90mm

 Control Box: 34cm x 30cm x 15cm

 TDL Cable: 3 meters (between sensor head and control box)

 Power, RS-232, T/A Aux. Input: 3 or 5 meters


 Sensor Head: ~2.5kg; Control Box: ~1.5kg

 Environmental Adaptability


  • Model:HT-1800 The Most Cost-effective Open-path Laser Hygrometer


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