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Recent tests carried out on Michell Instruments’ Optidew chilled mirror hygrometer confirm that it meets the Code of Federal Regulations for Engine Testing: an essential requirement for any instrument used for emissions testing in the US and many other regions. The Optidew is said to be ideal for monitoring engine test cell inlet air where consistency of measurements and long-term reliability are vital.

The code (CFR Title 40, Part 1065, Engine Testing Procedures) sets out a number of criteria that humidity measurement instruments must meet, and Michell’s Optidew Hygrometer exceeds each of these:

  • the Optidew has an accuracy of ±0.2°C — twice better than the required dew-point accuracy of ±0.5°C
  • the Optidew has a repeatability of 0.1°C — five times better than the required repeatability of 0.5°C
  • the Optidew updates its digital outputs every five seconds, or 0.2Hz twice as frequent as the required data update frequency of 0.1Hz, or once every 10 seconds
  • the Optidew consistently has less than 0.008°C noise on its outputs. The maximum output noise level is 0.02°C
  • the complete system rise and fall time, which is the time taken for the sensor to heat or cool from 10 per cent to 90 per cent of its range, should be no more than 50 seconds — the Optidew has a total rise/fall time of less than 45 seconds.

The rugged 316 stainless steel Nema 4/IP66 wall-mount enclosure is suitable for installation in an engine test room, while the remote sensor can be mounted directly into the engine air-intake ducting. The Optidew gives reliable results because it measures a primary characteristic of moisture — the temperature at which condensation forms on a surface. With no calculated variables that can shift over time, the Optidew is said to be ideal for monitoring engine test cell inlet air where consistency of measurements and long-term reliability are vital.

Key specifications and benefits

  • Twice as accurate as required by the Code of Federal Regulations
  • Repeatability five times better than required by the Code of Federal Regulations
  • Digital output updated every five seconds
  • A rise and fall time of less then 45 seconds

Michell Instruments

Michell Instruments is an international leader in high-precision sensing with over 35 years’ experience in the field, specialising in instrumentation for dew point, relative humidity and oxygen analysis. The company serves industries as diverse as petrochemical and pharmaceutical to power generation and food processing. The product range includes:

  • High-precision ceramic moisture sensors to measure trace moisture in process applications.
  • Relative humidity transmitters and sensors for use in HVAC applications, pharmaceutical storage and other production processes where controlled environmental conditions are crucial.
  • Humidity calibration systems and reference dew-point hygrometers enable customers to carry out the calibration of portable hygrometers and relative humidity instruments in-house, saving on downtime and costs.
  • Zirconia and thermo-paramagetic oxygen analysers for combustion optimisation, maintaining gas purity, controlling levels of CO2 in breweries and many other applications.
  • Condumax II Hydrocarbon dew point analysers ensure the quality of natural gas at custody transfer, prevent gas burner failure and the prolong the life of process equipment, helping companies save millions of dollars on repairs and downtime.
  • Trace moisture in hydrocarbon liquids analysers are available in explosion-proof and instrinsically safe versions and allow the continuous measurement of moisture content in a wide range of applications from transformer oil, petrochemical factions and pure hydrocarbons.
  • Process moisture analysers provide continuous on-line measurements of trace moisture in process gases and are available as explosion-proof, instrinsically safe and laboratory versions.

Michell Instruments has three manufacturing locations: Oosterhout, The Netherlands; Lyon, France and Ely, UK. The company has an extensive network of factory-trained application engineers, subsidiaries and distributors stretching across 56 countries.

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