MOP301 – Insertion Moisture in Oil Probe with Modbus RTU


The MOP301 insertion probe measures accurately water activity (aw) and temperature (T) in lubrication, hydraulic and insulation oil. In addition it calculates the absolute water content of the oil (x) in ppm.  The slide fitting allows for easy installation and removal under pressure up to 20 bar.

MOP301 probe for moisture in oil with optional ball valve pressure tight up to 20 bar

MOP301 probe for moisture in oil with slide fitting

Moisture in oil probe MOP301 with Sigma 05

Precise and reliable measurement of oil moisture 
The E+E humidity sensor elements used in the MOP301 are characterised by particularly good long-term stability and resistance to contamination. They are the basis for the high accuracy and reliability of the moisture and temperature measurement.

Versatile in Use
Mechanically, the MOP301 impresses with a robust stainless steel housing with protection class IP66, an oil-resistant cable and a moulded M12x1 plug connection. It can be used in a temperature range from -40 to 120 °C and up to 20 bar pressure.

Different probe and cable lengths as well as the slim design allow a particularly flexible installation of the MOP301. Thanks to the practical process connection with ISO or NPT thread, the immersion depth can be set precisely. With the aid of an optional ball valve, the sensor can be installed and removed without interrupting the process.

Measured values and interfaces  
The MOP301 provides the moisture content of the oil as an absolute or relative value. The water activity (aw) provides information about how close the oil is to the saturation point at a certain temperature. The water content (x) indicates in absolute terms the moisture level is expressed as water content (x) in ppm, representing mg water / kg oil. Based on the measured water activity (aw) and temperature, the MOP301 calculates the absolute water content (x) in ppm.

The oil-specific parameters required for the calculation can already be preconfigured when ordering or can be stored with the help of the PCS10 Product Configuration Software.

Typical applications

Monitoring of

    • transformer oil
    • lubrication oil
    • hydraulic oil
    • diesel fuel

Sigma 05 – Modular Sensor Platform

The MOP301 is compatible with the Sigma 05 host device of the E+E Modular Sensor Platform. Together they become a versatile, plug-and-play moisture in oil and temperature sensor with interchangeable probe, analogue outputs and optional display. Besides MOP301, Sigma 05 accommodates also other E+E intelligent sensing probes. See Sigma05 for further details.

Key Features

  • High measurement accuracy and wide temperture range
  • Suitable for transformer, lubrication and hydraulic oil
  • Process connection with ISO or NPT slide fitting
  • Pressure tight up to 20 bar with the optional ball valve
  • Calculation of water content x [ppm]
  • Stainless steel enclosure and filter cap with IP66 rating
  • RS485 with Modbus RTU
  • Editable Modbus-Map Area
  • Moulded M12x1 connector
  • Oil resistant cable

Technical Data

Measuring Range
0...1 aw
-40...120 °C (-40...248 °F)
±0.02 aw
±0.15 °C
Digital Interface
RS485 with Modbus RTU
8-35 V DC

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