Optical Dew-Point Transmitter
The Optidew precision optical dew-point transmitter is based on the proven, fundamental optical dew-point measurement principle, giving long-term drift-free performance. It offers a wide measurement range from the equivalent of <0.5 to 100% RH at ambient temperature (dew point range: -40 to +90°C (-40 to +194°F), and up to +130°C (+266°F) with high temperature option).

The Optidew is ideal for industrial applications and is supplied in a rugged NEMA 4X (IP66) stainless steel wall mount enclosure. The transmitter provides two linear 0/4-20 mA outputs and RS232 serial communications, allowing configuration and monitoring by a suitable computer or PLC system or via specific Optidew logging software. An adjustable isolated alarm contact allows Optidew to be used for direct process control.

Product Features

  • Precision process dew point, %RH and temperature measurement
  • Measurement Range: <0.5 to 100% RH,
    -40 to +90°Cdp (-40 to +194°F)
  • ±0.2°Cdp (±0.36°Fdp) accuracy (±0.15°C (±0.27°F) optional)
  • Fundamental drift free dew-point measurement
  • Rugged NEMA 4X industrial housing
  • High temperature sensor option to +130°C (+266°F)
  • Optional local display

Technical Specification

Measurement Accuracy* ±0.2°Cdp (±0.32°F)
±0.15°Cdp (±0.27°Fdp) accuracy optional
±0.1°C (±0.18°Fdp) temperature
Measurement Units °C, °F dew point; %RH; °C, °F temperature; g/m3; g/kg; aW; ∆ (t-t dew point)
Response Speed 1°C/sec plus settling time (dew point dependant)
Power Supply 90 to 264 V AC OR 127 to 370 V DC, 47 to 440 Hz, 20 W max. Internally fused, 4A quick blow
Dew-Point Sensor
Sensor1 Stage2 StageHigh temp PEEK
Dew-Point Range-30°Cdp @ sensor temp of 20°C
(-22°Fdp @ sensor temp of 68°F)

+90°Cdp @ sensor temp of 90°C
(+194°Fdp @ sensor temp of +194°F)
-40°Cdp @ sensor temp of 20°C
(-40°Fdp @ sensor temp of 68°F)

+90°Cdp @ sensor temp of +90°C
(+194°Fdp @ sensor temp of +194°F)
-40°Cdp @ sensor temp of 20°C (-40°Fdp @ sensor temp of 68°F)

+130°Cdp @ sensor temp of 130°C (+266°Fdp @ sensor temp of 266°F)
Temperature Range-40 to +90°C
(-40 to +194°F)
-40 to +90°C
(-40 to +194°F)
-40 to +130°C
(-40 to +266°F)
%RH Range<2 to 100%<0.5 to 100%<0.5 to 100%
Min Measured Dew Point @ +20°C (+68°F)-30°C (-22°F)-40°C (-40°F)-40°C (-40°F)
Mirror Material Options Gold plated copper (standard)
Gold stud
316 stainless steel stud**
Platinum stud**
**Recommended for special applications only, consult Michell Instruments before ordering
Sensor Body Material Options Acetal (standard)
High temperature PEEK
316 stainless steel**
Anodized aluminum**
**Recommended for special applications only, consult Michell Instruments before ordering
Temperature Measurement 4 wire Pt100, 1/3 DIN class B
Sample Flow 0.1 to 2 Nl/min (0.21 to 4.23 scfh) (in sampling block)
Maximum Velocity 10 m/sec (32.8 f/sec) direct insertion
30 m/sec (98.4 f/sec) with sintered guard
Pressure Standard unit: 2 Mpa / 20 barg / 290 psig (max)
Ingress Protection: IP66
High Pressure version: 25 Mpa / 250 barg / 3626 psig (max)
Ingress Protection: IP65
Cable Length 2m (6.6'); 50m (164') maximum (up to 250m (820') on special request)
Remote PRT
Temperature Measurement 4-wire Pt100 1/10 DIN class B
Cable Length 2m (6.6'); 50m (164') maximum (up to 250m (820') on special request)
Transmitter Electronics
Resolution 0.1 for °C, °F and %RH
0.01 for g/m3 and g/kg
Outputs Analog: Two channels 0/4-20 mA
Digital: RS232 (RS485 optional)
Alarm: Volt free contact, 2 A @ 30 V DC
Status LEDs DCC / Alarm Status
Operating Temperature -20 to +50°C (-4 to +122°F) ambient
Enclosure 304 stainless steel
Ingress Protection IP66 (NEMA 4X)
Cable Pack Power and RS232 cables
Calibration 4-point traceable in-house calibration as standard, UKAS accredited calibrations optional – please consult Michell Instruments
*Measurement accuracy means maximum deviation between instrument under test and corrected reference. To this must be added the uncertainties associated with the calibration system and the environmental conditions during testing and subsequent use

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