Vaisala MMT310 Moisture & Temperature Meter Series


  • Continuous measurement of moisture in oil
  • Proven Vaisala HUMICAP sensor, over 15 years in oil applications
  • Measurements in lubrication, hydraulic and transformer oils
  • Excellent pressure andtemperature tolerance
  • Measuring water activity – ppm calculation for transformer oil
  • Small size, easy to integrate
  • Traceable calibration for measurement and analog outputs (certificates included)

Dpstar is a leading supplier of environmental measurement sensors for temperature, relative humidity, pressure, dew point, CO2, and other environmental condition monitoring for industrial process application and research. Since the ’90s, we earned a reputation as a trusted partner to our clients through our commitment and dedication. We are an authorized distributor and supplier of measuring sensors solutions from renowned manufacturers Vaisala. Vaisala is a global leader in environmental and industrial measurement. Building on 80 years of experience, Vaisala provides observations for a better world. Vaisala is a reliable partner for customers around the world, offering a comprehensive range of innovative observation and measurement products and services.

Vaisala MMT310 series uses the newest Vaisala HUMICAP sensor for precise moisture measurement in liquid hydrocarbons. This sensor is highly resistant to chemicals, ensuring accurate and dependable readings across a broad range. Vaisala HUMICAP Moisture and Temperature Transmitter Series for Oil Vaisala MMT310 is a fast and reliable online detector for moisture in oil.

Vaisala MMT310 measures moisture in oil using water activity (aw) and temperature (T). Water activity shows if there’s a risk of freewater forming, regardless of oil type, age, or temperature.


Key Benefits

Online, real-time detection of moisture in oil without sampling.

Easy to install and operate
Installation through ball valve. No need to shut down the process.

Tells the true margin to water saturation point in all changing conditions, taking into account e.g. temperature changes and aging of oil.


Vaisala MMT310 can be used in lubrication and hydraulic systems as well as in transformers. It can be used for on-line moisture monitoring and as a control function, allowing separators and oil purifiers to be started only when necessary.


Measurement Performance
Water Activity
Measurement range aw (%RS) 0 … 1 (0 … 100 %)
Accuracy (Including Non-Linearity, Hysteresis, and Repeatability):
0 … 0.9 (0 … 90 %)
0.9 … 1.0
Response time (90 %) at +20 °C in still
oil (with stainless steel filter)
10 min
Sensor Vaisala HUMICAPâ 180L2
Measurement range (-40 … +180 °C) (-40 … +356 °F)
Typical accuracy at +20 °C (68 °F) ±0.2 °C (±0.36 °F)
Sensor Pt100 RTD Class F0.1 IEC 60751
Mechanical Specifications
IP rating IP66
Weight example: MMT317 with 2 m
cable (Weight depends on selected probe
and cable)
476 g
Cable feed through alternatives 8-pole connector with 5 m cable Female 8-pin connector screw joint for cable diameter 4 … 8 mm
Sensor protection Stainless steel grid standard filter
Stainless steel grid filter for high flow rates (> 1 m/s)
Transmitter housing G-AlSi 10 Mg
Transmitter base PPS
Probe Cable Length
MMT317 2 m, 5 m, or 10 m
MMT318 2 m, 5 m, or 10 m
Probe installation MMT317
Swagelokâ NPT 1/2″, ISO 3/8″ or ISO 1/2″
Probe installation MMT318
Fitting bodies ISO 1/2″, NPT 1/2″
Spare Parts and Accessories
Rain shield ASM211103
USB cable 238607
Stainless steel filter HM47453SP
Stainless steel filter (high flow rate) 220752SP
Ball-Valve Set BALLVALVE-1
Operating Environment
Operating temperature for electronics (-40 … +60 °C) (-40 … +140 °F)
Storage temperature (-55 … +80 °C) (-67 … +176 °F)
Pressure range for MMT318 with ballvalve
up to 120 °C
0 … 40 bar
Pressure range for MMT317 0 … 10 bar
EMC compliance EN61326-1, Industrial environment
Inputs and Outputs
Two analog outputs, selectable and scalable 0 … 20 mA or 4 … 20 mA
0 … 5 V or 0 … 10 V
1 … 5 V available through scaling
Typical accuracy of analog output at +20 °C ±0.05 % full scale
Typical temperature dependence of analog output 0.005 %/˚C (0.003 %/°F) full scale
Serial output RS-232C
Connections 8-pole connector with RS232C, current/ voltage outputs (two channels) and Uin
Operating voltage 10 … 35 VDC
External load RL < 500 Ω
Startup time after power-up 3 s
Minimum Operating Voltage
RS232C output 10 VDC
Analog output 15 VDC
Pressures above 10 bara (145 psia) 24 VDC
Power Consumption
RS232C 12 mA
Uout 10 V (10 kΩ) Channel 1 & channel 2 12 mA
Iout 20 mA (load 511 Ω) Channel 1 & channel 2 50 mA


Vaisala-MMT310-Moisture and Temperature Meter Series_DpstarGroup