MMP8 / MMT143 / MMT310 / MMT162 — HUMICAP moisture sensors for transformer oil
MMP8, MMT143, MMT310 and MMT162 are HUMICAP-based moisture sensors for continuous online monitoring of transformer oil. They measure water activity, relative saturation and temperature and calculate moisture content in ppm. The flagship MMP8 probe operates in the range −70…+180 °C.
- Sensor
- HUMICAP (capacitive thin-film polymer), MMP8 with HUMICAP 180L2
- Quantities
- water activity aw, relative saturation %RS, temperature; ppm calculation for transformer oils
- MMP8
- range −70…+180 °C; accuracy up to ±0.02 aw / 2 %RS, temperature up to 0.1 °C; probe 262 or 448 mm; Modbus RTU/RS-485; installation through a ball valve
- MMT143
- 0–100 %RS, accuracy ±2 %RS (0–90 %), ±3 %RS (90–100 %); −40…+80 °C (±0.2 °C); IP66, stainless steel; RS-485 Modbus; 5–28 V (digital) / 18–28 V (analogue)
Price, availability and lead time on request. We help with analogue selection, customs clearance and delivery.
Description
HUMICAP-based moisture sensors continuously monitor moisture in transformer, lubricating and hydraulic oils. Moisture lowers the breakdown voltage of transformer oil and accelerates ageing of paper insulation, so without moisture monitoring the monitoring of a power transformer is incomplete. HUMICAP works as a capacitive thin-film polymer sensor with resistive temperature measurement, and has been used in oil environments for over 20 years.
The devices measure water activity (aw) and relative saturation (%RS) together with temperature. These quantities show directly whether there is a risk of free water forming, and they do not depend on the type, age or temperature of the oil. For mineral transformer oils the absolute moisture content in ppm is calculated immediately. For other oils the conversion coefficients are programmed if the water solubility is known.
The MMP8 heads the Indigo family and has the HUMICAP 180L2 sensor. The temperature range is −70…+180 °C, the accuracy is up to ±0.02 aw (2 %RS) and up to 0.1 °C for temperature, and sensitivity in the dry range is high, which is essential for transformers. Factory calibration is done at five humidity points and one temperature. The probe is made in lengths of 262 and 448 mm and is installed and removed on a running process through a ball valve with adjustable depth and an ISO or NPT 1/2 connection. The probe works standalone via Modbus RTU/RS-485 or connects to the Indigo520/510/300 transmitters, the Indigo80 handheld and the Insight software. A DNV GL certificate is available for the 262 mm probe.
The MMT143 is intended for OEM use. The range is 0–100 %RS, the accuracy is ±2 %RS up to 90 % and ±3 %RS above, and the temperature is −40…+80 °C (±0.2 °C). The enclosure is IP66 stainless steel, the interface is RS-485/Modbus, and the supply is 5–28 V for the digital output or 18–28 V for the analogue output. Deliveries start in the third quarter of 2026.
The MMT310 series covers fast online transmitters for transformer oil and for lubrication systems of ships and the paper industry, which are also installed through a ball valve without stopping the process. The compact MMT162 with an RS-485/Modbus output is being discontinued, and the manufacturer recommends alternatives for new projects.
Technical specifications
| Sensor | HUMICAP (capacitive thin-film polymer), MMP8 with HUMICAP 180L2 |
|---|---|
| Quantities | water activity aw, relative saturation %RS, temperature; ppm calculation for transformer oils |
| MMP8 | range −70…+180 °C; accuracy up to ±0.02 aw / 2 %RS, temperature up to 0.1 °C; probe 262 or 448 mm; Modbus RTU/RS-485; installation through a ball valve |
| MMT143 | 0–100 %RS, accuracy ±2 %RS (0–90 %), ±3 %RS (90–100 %); −40…+80 °C (±0.2 °C); IP66, stainless steel; RS-485 Modbus; 5–28 V (digital) / 18–28 V (analogue) |
| MMT310 | series of transmitters for transformer, hydraulic and lubricating oils; installation through a ball valve |
| MMT162 | compact, RS-485 Modbus (being discontinued) |
| Compatibility | Indigo520/510/300, Indigo80, Insight PC |
Request a price and lead time
MMP8 / MMT143 / MMT310 / MMT162 — HUMICAP moisture sensors for transformer oil. We reply within one business day.
Or email sales@usk.ua or call 044 339-50-20.
Customs codes
| UKTZED (Ukraine) | 9025 80 40 00 |
|---|---|
| HS, 6 digits | 9025 80 |
| CN (EU) | 9025 80 40 |
| HTSUS (USA) | 9025 80 20 00 |
| China customs tariff | 9025 80 00 90 |
Codes are for reference: the final code is determined at declaration for the specific model.
Questions and answers
What accuracy does the MMP8 probe have?
Up to ±0.02 aw (2 %RS) for humidity and up to 0.1 °C for temperature. The operating range is −70…+180 °C.
Can the sensor be installed without shutting down the transformer?
Yes, the MMP8 and the MMT310 series are installed and removed on a running process through a ball valve. The MMP8 probe is 262 or 448 mm long.
What interface and supply does the MMT143 have?
RS-485 with the Modbus protocol, with a supply of 5–28 V for the digital output or 18–28 V for the analogue output. The enclosure is IP66 stainless steel.
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