Chilled Mirror Hygrometer
The Optidew 401 and Optidew 501 are fast-responding chilled mirror hygrometers utilizing the latest developments in chilled mirror technology. Ideal for use in industrial humidity control and precision laboratory applications. Available in bench top and wall mount configurations as well as a transmitter version of the Optidew 501 (without a display). Featuring ±0.15 °C accuracy across its -40 to +120 °C dew-point measurement range.

Product Features

  • New chilled mirror hybrid sensor gives fast dynamic response to changes in humidity
  • Accurate to ±0.15°C dew point, ±0.1°C temperature
  • Wide measurement range from -40 to +120°C dew point
  • Choice of communication methods, including Modbus TCP over Ethernet communication for easy networking
  • Optional pressure transmitter for accurate calculation of ppmv & g/kg

Technical Specification

Dew Point Measurement Accuracy ±0.15°C
Repeatability ±0.05°C
Sensitivity ±0.01°C
Response Stable measurement at +10°C dp within 1 minute
Dew-Point Sensor
SensorSingle StageDual StageHarsh Environment
Dew-Point Range(°C)-25 to +90°C-40 to +90°C-40 to 120°C
Temperature Range(°C)-40 to +90°C-40 to +90°C-40 to +120°C
%RH Range @ 23°C2.25 to 100% RH0.45 to 100% RH0.45 to 100% RH
MaterialPOM (head) Aluminium (body)POM (head) Aluminium (body)PEEK (head) Aluminium (body)
Corrosion & Saturation Protection Active Component Isolation System
Mirror Temperature Measurement Pt1000, Class A
Recommended Sample Flow Ambient (environmental measurements) to 2Nl/min (flowing sample)
Pressure 2500 kPa max
Process Connection M36x1.5
Remote PRT
Temperature Measurement Accuracy ±0.1°C
Temperature Measurement PT100, Class A
Cable Length 0.3, 3, 5, 10 and 20m lengths available
Maximum operating temperature Standard: 90°C max. High temperature: 120°C max.
Remote Pressure Sensor (Optional)
Pressure Measurement Accuracy ±0.25% FS
Pressure Measurement Range 0-160 kPa OR 0-2500 kPa
Process Connection 1/8” NPT-M
Control Unit
Resolution 1 or 2 decimal places selectable
Measurement Units °Cdp or °Fdp, Relative humidity - %, Absolute humidity - g/m3, ppmV, Mixing Ratio - g/kg, Wet Bulb Temperature (Twb) - °C, °F, Water Vapor Pressure (wvp) - Pa, Ambient Temperature - °C, °F, Pressure converted DP - °C, °F, Pressure - kPa, Bara, Barg, Psia, Psig
Enclosure Wall Mount - Optidew 501 Bench Top - Optidew 401
Material ABS ABS
Analog Outputs Two 0/4-20mA outputs (maximum load 500Ω) Two 0/4-20mA outputs (maximum load 500Ω)
Digital Communications Modbus RTU over RS485 (standard)
Modbus TCP over Ethernet (optional)"
Modbus RTU over:
USB (standard)
RS485 (standard)
Modbus TCP over Ethernet (optional)"
Alarms 1x Process Relay,
1x Alarm Relay,
Both Form C, 1A, 30Vdc.
1x Process Relay,
1x Alarm Relay,
Both Form C, 1A, 30Vdc"
Inputs 4-20mA for pressure sensor 4-20mA for pressure sensor
Data Logging SD card slot (optional) SD card slot (standard)
Ingress Protection IP54 (standard), IP65 (optional) IP54
Dimensions 220x175x75mm 220x175x118mm
Weight Control unit: 1.5kg, Sensor: 200g Control unit: 1.5kg, Sensor: 200g
Display 5.7” colour touch screen (optional) 5.7” colour touch screen
Environmental Conditions -20 to +50°C, up to 100%RH non-condensing (optional) 100% RH condensing with IP65 connector version
Supply Voltage 100 to 240VAC, 50 to 60Hz
Power Consumption 30VA max


Metrology Research & Development

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