DEWRay On-line Dewpoint Hygrometer 


  • Measurement of dewpoint temperature
  • Split-beam reflex optical system
  • AZOR Self-cleaning mirror function
  • 2 independent current outputs 4-20mA and 0-20mA
  • 2 independent alarm outputs
  • Aluminum housing
  • Sensor Head ingress protection to IP65
  • Supply voltage 85V-264VAC
  • Display in Dewpoint °C, °F and gm-3, %RH.
  • Interface RS-232 (RS-485option)



The DEWRay On-line is a precision chilled-mirror dewpoint hygrometer for the measurement of moisture in air or gases. The operating principle is based on continuous measurement of the dewpoint (or frostpoint) temperature of a gas.Inside the sensor head is a gold-plated copper mirror which is cooled by a two stage Peltier element and an optical dew detection system. A Pt100 resistance thermometer measures mirror temperature.
Formation of dew or frost on the mirror surface is detected by the optical system. The temperature at which this happens is known as the dewpoint temperature.It is a well known physical phenomenon that when water vapor in a gas condenses at temperatures below the freezing temperature, super-cooled water may condense instead of ice. The problem is unpredictable. On a new and clean mirror, super-cooled water may form even at temperatures as low as -48°C, in other cases ice may form immediately. This can give significant measurement errors of as much as 4°C in this type of instrument. Some manufacturers of cooled-mirror hygrometers add a microscope to the instrument so that an operator can confirm by human eye if  ice or water is present. Others induce formation of ice by a deep freezing cycle.

DEWRay Dewpoint Hygrometer utilizes a special technique to detect the presence of super-cooled water. This is a technological breakthrough in cooled mirror instruments. Thanks to the instrument's split-beam reflex optical system (see technology section), DEWRay recognizes the presence of super-cooled water on the mirror surface and automatically corrects the reading with reference to ice. According to practice in national standards laboratories, correct dewpoint measurement is always made with reference to ice and not with reference to super-cooled water.


A further feature employed in the DEWRay is self-cleaning system for the mirror. The AZOR - Automatic Zero Optical Reset system (see technology section for detailed information).      
There is no need with DEWRay to verify whether ice or water is on the mirror surface with a microscope. AZOR and the split-beam reflex optical detraction technology mean that that DEWRay may be employed in continuous unsupervised industrial measurement roles.


The DEWRay set comprises a panel mounting monitor unit, sensor head provided with sintered stainless steel filter, connecting cable and an additional Pt100 temperature sensor (optional) used when the unit of measurement desired is Relative Humidity. The instrument is provided with user configurable outputs: Two analog (4-20mA and 0-20mA) and two alarm outputs. Full configuration is available from the front panel or by parallel interface RS-232 (RS-485).


DEWRay chilled-mirror dewpoint hygrometer



Measuring range: -40 to +60°C
Accuracy for dewpoint: +/- 0.2°C
Accuracy for temperature: +/-0.1°C
Measurement Units: Cdp, Fdp, %RH, gm-3, aw,
Resolution: 0.1°C
Analog output: 2 channels 4-20mA, 0-20mA
Alarm output:  2 Alarm/switching contacts, 5A 250V AC/24V DC programable
Interface: RS-232 or RS-485
Power supply (standard): 85-264 V AC  47/440 Hz, 15VA
Operating Temperature:  -10°C to +40°C
Ingress protection: IP41 For front panel,  IP20 for rear of instrument
Filter sintered stainless steel
Mirror copper, gold plated
Mirror temperature: sensor Pt100, 1/3 DIN, 4 wire
Maximum gas velocity: 10 m/s
Maximum operating pressure: 0,1 MPa
Process Connection: M36 x 1.5
Connecting cable length: 3m, 5m, 7m
Ingress protection: IP65
External temperature sensor: Pt100, 1/3 DIN, 4 wire                        




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