HMP378F probe option for measuring oil moisture and temperature - HMT370EX

HMT370EX User Guide

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English (United States)
Document type
User guide

The HMP378F probe option is a variant of the standard HMP378, designed for measurements in oil. The mechanics of the probe are the same as in the standard HMP378 probe option (see HMP378 probe for pressurized pipelines).

The default HMP378F calculation coefficients (see HMP378F calculation model with average oil coefficients) are valid for transformer oil. Typically, moisture in transformer oil measurement with HMP378F has a ppm accuracy of ±10 % of the reading. If required, different oil-specific calculation coefficients can be configured into use to customize HMP378F measurements. For instructions, see Configuring calculation coefficients.

HMP378F uses the HUMICAP® 180L2 sensor designed specifically for oil and fuel measurements. For HUMICAP 180L2 sensor specifications, see Table 2.

The following measurement parameters are available for HMP378F:

Table 1. HMP378F measurement parameters
Parameter Abbreviation Unit
Temperature T °C (°F)
Relative saturation RS %RS
Water activity aw -
Water concentration in oil 1 H2O (oil) ppmw
1 The default calculation coefficients for water concentration in oil (ppmw) are valid for mineral transformer oil. For more information on default and oil-specific calculation coefficients, see HMP378F calculation model with average oil coefficients and HMP378F calculation model with oil-specific coefficients.