about us our products   moisture calculator contact us home

Dewpoint Transmitters


Model CMH Chilled Mirror Hygrometer

  • Primary Measurement technique. Traceable to NPL/NIST.
  • Reduced maintenance requirements.
  • Easy to read, LED display
  • Programmable menu via front panel
  • Depression range of either 45 or 60║F - one or two stage cooling.
  • Two alarms (form C), automatic balance control, Scaleable analogue outputs etc - all come as standard
  • Scan feature - view multiple parameters at 3s intervals
  • ABC: Automatic Balance Cycle
    • automatically corrects for most mirror contaminants
    • automatically re-standardizes instrument
    • maximizes length of unattended operation

The CMH Series is a range of chilled mirror dew point hygrometers, designed to give a primary measurement of water vapour content of gases. These self contained dew point hygrometers combine the inherent accuracy, reliability and long term stability of optical chilled mirror technology with the convenience and ease of use of demanded by Industry.

The Model CMH dewpoint hygrometers are designed for continuous monitoring applications where high accuracy and reliability are required. Typical applications include: Dewpoint temperature measurement is made using a direct measuring sensor utilising a Peltier-cooled mirror, automatically held at the dew point temperature by a condensate detecting optical system, incorporating an LED light source and photo-detector. The optical sensing bridge detects the change in light level when dew or frost forms on the mirror. Subsequent cycles of negative feedback controlled heating and cooling refine the result to a highly accurate constant reading of sample dew point. This technique is a primary measurement of the water vapour content of the gas.

The mirror temperature represents the true dew point temperature and is measured by an embedded precision platinum resistance thermometer. For dew points below 0°C, the instrument displays the frost point.

(For full details please request specification sheet Model CMH Series)


CMH.pdf data sheet
(requires Adobe acrobat)

alpha moisture systems
Alpha House, 96 City Road
BRADFORD, ENGLAND BD88ES
t:+44 (0)1274 733 100  f:+44(0)1274 733 200