Optica Chilled Mirror Hygrometer

Chilled mirror hygrometer with Ethernet interface and single stage sensor.

The inherent accuracy and long term stability provides many advantages over other types of humidity measurement technologies. Chilled mirrors fundamentally measure the dew or frost point temperature directly by controlling a reflective surface to an equilibrium temperature between dew/frost formation and evaporation, and precisely measuring the temperature of the mirror at this point.  Fundamental dew point measurement is a primary measurement used as a transfer standard for calibrating other humidity instruments and sensors. Chilled mirrors are also the sensors of choice when process and laboratory measurements call for high precision without long term drift. The accuracy of the dew point measurement has been validated to an accuracy of ±0.36°F (±0.2°C) dew/frost point. The precision can also be enhanced to ±0.27°F (±0.15°C) dew/frost point. Dry bulb temperature is measured with a precise four-wire 100 S platinum RTD and pressure is measured with a piezoresistive silicon pressure transducer. Gas flowrate across sensor in the range of 0.25 to 2.5 L/min is required. The cardinal measurements of dew/frost point, dry bulb temperature and pressure are used to calculate other humidity parameters such as relative humidity, wet bulb, mass mixing ratio, volumetric mixing ratio, absolute humidity, enthalpy and water vapor pressure values using psychometric equations. System includes software to integrate into Fideris FCPower control software for data logging, charting, and full process automation.

Optica Measures

  • Temperature
  • Relative humidity (% RH)
  • Dew/frost point (Td)
  • Absolute humidity (m/v)
  • Mass mixing ratio (m/m)
  • Volume mixing ratio (v/v)
  • Wet bulb (Tw)
  • Enthalpy (h)
  • Water vapor pressure (e)
  • Pressure
  • Alarm relays
  • Analog outputs



  • Ethernet port
  • Java-based applet loads in web browsers
  • Data logger 6 megabyte memory
  • Recorded data uploads in ASCII format
  • Exports to spreadsheets
  • Real time "strip chart" graphing
  • Color VGA or 4 x 40 matrix display
  • Integrate into Fideris FCPower control software


Integrate with Fideris FCPower for a powerful user-friendly experience

Applications In the Lab or on the Plant Floor
-Calibration labs
-Process control
-Clean rooms
-Environmental test chambers
-Precision HVAC monitoring and control
-Fuel cells
-Heat exchanger and refrigerant coil calorimeters
-Thermal processing/heat treating
-Semiconductor manufacturing
-Storage areas
-Pharmaceutical validation chambers
-Aircraft engines and turbines