Hand-Held Moisture Meter for Transformer Oil TES-MM70


The MM70 enables reliable detection of moisture in mineral-based transformer oil. It primarily measures the moisture of the oil as water activity (aw), but in this version the reading is converted into a ppm output calibrated for mineral-based transformer oils. The probe can be inserted (and removed) directly into the transformer oil through the supplied ball valve without draining the system.

The MM70 also supports the use of Vaisala's humidity, dew point, and carbon dioxide probes, making it a versatile investment applicable to several multi-parameter applications. Two probes can simultaneously be connected to the MM70.

The MI70 Link Windows® software and the USB connection cable form a practical way for transferring logged and real time measurement data from the MM70 to a PC.



  • MI70 hand-held indicator
  • MMP78 moisture in oil probe
  • Manual press tool for installation
  • Calibration certificate (ISO9001 compliant, traceable to NIST)
  • Ball valve set with welding joint, fitting body and blanking plug
  • Rechargeable battery pack and universal AC adapter
  • MI70LINK software with USB cable
  • Professional carrying case



Measurement parameter(s) Moisture (ppm)
Measurement range 0 ... 1 aw
-40 ... +100 °C (-40 ... +212 °F) T
Measurement accuracy ±0.02 (0 ... 0.9 aw)
±0.03 (0.9 ... 1.0 aw)
±0.2 °C (±0.36 °F) T
Operating temperature -40 ... +60 °C (-40 ... +140 °F)
Operating pressure 0 ... 20 bar (0 ... 290 psi)
Operating voltage Rechargeable NiMH battery pack and universal AC adapter
Analog outputs 0 ... 1 V
Housing classification IP65 (NEMA 4) for probe
IP54 for MI70 indicator

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