Vaisala MMP8 Moisture in Oil and Temperature Probe

The Vaisala MMP8 provides continuous online measurement of dissolved moisture and temperature in transformer oil, lubrication oil, hydraulic fluid and other liquid hydrocarbons.

Measures water activity from 0 to 1 a_w, relative saturation, temperature and ppm_w
Dry-end accuracy up to ±0.01 a_w or ±1%RS
Temperature measurement from −40 to +180 °C
Available in standard 262 mm and long 448 mm probe versions
Adjustable insertion depth with ISO 1/2 or NPT 1/2 process fittings
Standalone Modbus RTU or connection to Vaisala Indigo transmitters
Ask Seacom about the suitable MMP8 configuration

Description
Attachments

Continuous Moisture Measurement Directly in Oil

The Vaisala MMP8 measures dissolved moisture directly in a flowing or static oil system. It is designed for transformer oil, lubrication systems, hydraulic fluids, oil purification equipment and other applications where early detection of water ingress helps protect the oil, machinery and process.

The probe reports water activity, relative saturation and temperature. It can also calculate water concentration in ppm_w when suitable oil-solubility coefficients are available. Because the measurement intelligence is built into the probe, MMP8 can communicate directly with a control system or connect to a Vaisala Indigo transmitter or Indigo80 handheld indicator.

Choosing the system: Use MMP8 alone where the control system accepts Modbus RTU. Add an Indigo transmitter when the installation requires a local display, analogue outputs, relays, Ethernet, Modbus TCP or additional wiring and power-supply options.

Standard or Long MMP8?

Selection point	Standard MMP8	Long MMP8
Overall probe length	262 mm	448 mm
Adjustable insertion depth	35 to 193 mm	35 to 379 mm
Typical use	Standard pipelines, transformer valves and compact oil-system installations	Large pipes, tanks or installations requiring a deeper measurement point
Weight with 2 m cable	Approximately 510 g	Approximately 610 g
Marine type approval	DNV GL certificate applies	DNV GL certificate does not apply to the 448 mm version
Selection check	Confirm the required insertion depth and external service clearance	Confirm that the additional probe length can be safely inserted and removed

Measurement Performance

Specification	MMP8 performance
Water-activity range	0 to 1 a_w
Specified water-activity accuracy	±0.01 a_w, equivalent to ±1%RS, from 0 to 0.5 a_w under specified conditions
Response time	10 minutes, T90, at +20 °C in still oil
Moisture sensor	Vaisala HUMICAP® 180L2
Temperature range	−40 to +180 °C
Temperature accuracy at +20 °C	±0.2 °C
Water concentration	Typical ppm_w accuracy of 10% of the reading when suitable oil coefficients are used
Output parameters	Water activity, relative saturation, temperature and water concentration in oil
Calibration certificate	Traceable calibration at five moisture points and one temperature point

Operating and Mechanical Specifications

Specification	MMP8 provision
Probe-head temperature	−40 to +180 °C
Probe-body temperature	−40 to +80 °C
Operating pressure	0 to 40 bar absolute
Pressure during insertion	Up to 10 bar absolute
Ball-valve operating limit	Up to +100 °C and 40 bar absolute
Process fittings	ISO 1/2 or NPT 1/2
Probe-body protection	IP66
Probe material	AISI 316L stainless steel
Standard probe cable	2 m FEP-jacketed cable
Electrical connector	M12 5-pin A-coded male
Filter options	Standard stainless-steel grid or grid for oil-flow rates above 1 m/s

Standalone Output and Indigo Connectivity

Connection method	What it provides	Suitable when
MMP8 standalone	15 to 30 VDC supply and non-isolated RS-485 with Modbus RTU	The PLC, data logger or control system can communicate directly with the probe
Indigo200	Compact display with model-dependent analogue outputs, relays or Modbus RTU	A practical single-probe local transmitter is required
Indigo300	Industrial metal enclosure, local display and up to three configurable analogue outputs	A rugged single-probe transmitter is preferred
Indigo510	One-probe flagship transmitter with two isolated analogue outputs and Ethernet connectivity	A robust single-probe plant installation is required
Indigo520	Two probe connections, four isolated analogue outputs, two relays and Ethernet connectivity	Two measurements or expanded automation integration are required
Indigo80	Portable display, data logging, diagnostics and probe configuration	Spot checks, field diagnostics or portable moisture-in-oil measurement are needed
Vaisala Insight	Probe configuration, diagnostics, data viewing and field calibration	A service computer is available at the measurement location

MMP8, MMT310 or MMT330?

Instrument	Main strength	When to consider it
MMP8	Interchangeable smart probe with standalone Modbus RTU and full Indigo compatibility	New modular installations, portable work with Indigo80, or migration from legacy MMT330 systems
MMT310 Series	Compact fixed transmitter with two analogue outputs and RS-232C	Established installations requiring a compact permanently connected transmitter
MMT330 Series	Legacy full-size transmitter platform	Existing-unit identification and migration planning only; use MMP8 with Indigo for new projects
MMP8 with Indigo transmitter	Separates the calibrated probe from the display and system-interface hardware	Applications requiring maintainability, selectable outputs and future probe interchangeability

Typical Moisture-in-Oil Applications

Application	Measurement objective	Important consideration
Power transformers	Monitor dissolved moisture and the risk of free-water formation	Choose a representative oil-circulation point and confirm the required ppm coefficients
Lubrication systems	Detect water ingress before it affects the oil or rotating equipment	Trend moisture together with temperature and operating condition
Hydraulic systems	Track moisture that can shorten fluid and component life	Review pressure, temperature, flow and fitting compatibility
Oil dryers and purifiers	Measure drying performance and control treatment cycles	Compare inlet and outlet readings under stable process conditions
Marine machinery	Monitor moisture in lubricating and hydraulic oils	Use the standard 262 mm version where DNV GL type approval is required
Paper and process industries	Detect ingress and support preventive maintenance	Select an accessible measurement point with continuous oil exchange

Water Activity, Relative Saturation and ppm

Water activity, a_w, indicates how close the oil is to moisture saturation at its present temperature. Relative saturation expresses the same relationship from 0 to 100%RS. A rising value shows that the oil is moving closer to the condition where free water can form, even when the absolute amount of water has not changed.

Water concentration in ppm_w estimates the mass of water in the oil. The calculation depends on the water-solubility characteristics of the specific oil. Vaisala provides coefficients for several transformer oils, while other oils may require verified oil-specific coefficients. These can be configured using Vaisala Insight or Indigo80.

Vaisala MMP8 Supplier and Technical Support in Malaysia

Seacom Process Instruments supplies and supports the Vaisala MMP8 Moisture in Oil Probe in Malaysia for transformer oil, lubrication systems, hydraulic fluids, oil dryers, marine machinery and other demanding industrial applications.

Our team can assist with standard or long probe selection, process fittings, ball-valve installation, Indigo transmitter selection, Modbus integration, oil-specific ppm coefficients, commissioning and calibration planning. We can also review replacement arrangements for existing MMT330 and MM70 systems.

Need help selecting the right configuration? Send Seacom the oil type, temperature, pressure, pipe size, process connection, insertion depth, required outputs and whether the measurement will be fixed or portable. We will help check the suitable MMP8 and Indigo arrangement.

Download

MMP8 Catalogue (190.61k)

Indigo200 Catalogue (204.62k)

Indigo 500 Catalogue (581.96k)

MMT310 Series Catalogue (226.84k)

MMT330 Series Catalogue (570.34k)

Reference

Specific References

Download

Smart Moisture in Oil Probe MMP8 - MMP8 Catalogue (190.61k)

Indigo200 Series Transmitters for Vaisala smart probes for Vaisala Smart Probes - Indigo200 Catalogue (204.62k)

Indigo500 Series Transmitters for Vaisala smart probes - Indigo 500 Catalogue (581.96k)

Compact Moisture in Oil And Temperature Transmitter MMT310 - MMT310 Series Catalogue (226.84k)

Oil Moisture Transmitter MMT330 Series - MMT330 Series Catalogue (570.34k)

Vaisala MMT330 Moisture in Oil Transmitter Series – Discontinued

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Vaisala MMT330 Moisture in Oil Transmitter Series – Discontinued

The Vaisala MMT330 Series provided continuous measurement of moisture and temperature in transformer oil, lubrication oil, hydraulic fluid and other liquid hydrocarbons.

Discontinued series; not recommended for new installations
Legacy MMT332, MMT337 and MMT338 probe configurations
Measures water activity, relative saturation, temperature and calculated ppm
Graphical display, data logging and versatile analogue or digital outputs
Used for oil-condition monitoring, dryer control and free-water risk detection
Use Vaisala MMP8 with an Indigo transmitter for new installations

Compact Moisture in Oil And Temperature Transmitter MMT310 Series

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Compact Moisture in Oil And Temperature Transmitter MMT310 Series

The Vaisala MMT310 series incorporates the latest generation of the Vaisala HUMICAP® Sensor, developed for demanding moisture measurement in liquid hydrocarbons.

The sensor’s excellent chemical tolerance provides accurate and reliable measurement over the wide measurement range.

The MMT310 series 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.

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Vaisala Indigo510 and Indigo520 Flagship Transmitters

The Vaisala Indigo500 Series provides flagship industrial measurement integration: choose Indigo510 for a simplified single-probe system or Indigo520 for full dual-probe capability.

Indigo510: one probe and two isolated analog outputs
Indigo520: two probes, four isolated outputs and two relays
Ethernet web interface and Modbus TCP communication
Rugged IP66 and NEMA 4 metal enclosure

Indigo200 Series Transmitters for Vaisala smart probes for Vaisala Smart Probes

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Vaisala Indigo200 Series Transmitters

The Vaisala Indigo200 Series is the standard transmitter platform for one interchangeable Indigo-compatible smart probe, providing local display and practical automation-system connectivity.

Indigo201 with three analog outputs and two relays
Indigo202 with Modbus RTU and two relays
Colour display with numerical and graphical views
IP65 enclosure for industrial measurement applications

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Vaisala Indigo300 Industrial Transmitter

The Vaisala Indigo300 is a rugged industrial transmitter for one Vaisala Indigo-compatible smart probe, providing local measurement display and up to three configurable analog outputs.

Its corrosion-resistant IP66 metal enclosure, flexible probe mounting and interchangeable probe design make Indigo300 suitable for humidity, temperature, dew point, CO2, moisture in oil and other demanding industrial measurements.

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