SF72 Rail

Moisture Transmitter

A cost-effective moisture transmitter designed to continuously monitor the performance of the compressed air dryers on railway rolling stock to ensure both safety and efficiency of braking and other systems.

Using Michell’s latest generation of polymer moisture sensor to provide fast, reliable readings of dew-point, allowing for fast action to be taken by operators.

The transmitter itself has a heavy duty M12 electrical connector and is calibrated to measure within the range of -60 to +60°C dew point: wide enough to cope with extreme conditions found in railways around the world.

The sensor has the following rail-industry approvals:

  • EMC/RFI approval to rail standard EN50121-3-2
  • Shock/vibration approved to rail standard IEC16373:1999-01

Product Features

  • M12 electrical connector
  • Dew-point measurement range –60 to +60°Cdp
  • Fast response
  • 316 stainless steel IP66 construction
  • Traceable calibration certificate
  • Accuracy ±2°Cdp
  • G 1/2” BSP process connection

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Easidew Transmitter

Technical Specifications

Measurement range (dp) –60 to +60°C dew point
Accuracy (dp) ±2°C dew point
Repeatability 0.2°C dew point
Long term stability Less than 1% per year at reference conditions
Calibration Traceable 8-point calibration certificate
Electrical Specifications
Output signal 4-20 mA (2-wire connection, current source)
Output Dew point
Analog output scaled range Standard: –60 to +60°C
Non-standard available upon request
Supply voltage 12 to 28 V DC
Load resistance Max 250 Ω @ 12 V (500 Ω @ 24 V)
500 Ω @ 24 V
CE marked Certified
Operating Specifications
Start-up temperature Ambient: -40 to + +50°C
Gas: –40 to +70°C
Operating temperature Ambient: -40 to + +50°C
Gas: –40 to +60°C
Storage temperature –40 to +85°C
Operating pressure 45MPa (450 barg) maximum
Overpressure rating x2 operating pressure 90 MPa (900 barg)
Flow rate 1 to 5 Nl/min mounted in standard sampling block;
0 to 10m/sec (0 to 32.8 fps) direct insertion insertion
Temperature coefficient Characterized over operating range
Mechanical Specifications
Ingress protection IP66 in accordance with standard BS EN 60529:1992
Housing material 316 stainless steel
Dimensions L=119mm (including HDPE filter) x ø27mm
Filter Standard: HDPE guard <10µm
Process connection and material G 1/2” BSP, 316 stainless steel
Weight 150g
Electrical connections M12, 4 pin (A coded)
Digital diagnostic communications RS485, 2-wire Modbus RTU
Diagnostic Conditions
(Factory Programmed)
Sensor fault
Under-range dew point
Over-range dew point
23 mA
4 mA
20 mA
Rail Certifications
Shock and vibration IEC 61373:1999-01
RFI/EMC emissions and immunity EN 50121-3-2:2006

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Designed to make high-speed spot check measurements to -50°C dew point as simple as possible, simply connect your sample gas, turn on the instrument and it will automatically begin to measure the dew point of the applied sample.
MDM300 & MDM300 I.S. MDM300 & MDM300 I.S.
The MDM300 easy to use, ergonomic, portable dew-point hygrometer offers rapid spot-check measurements of dew point or moisture content. Available with optional ATEX, IECEx, FM, CSA and GOST certification.