Vaisala HMT370EX - HMP378 F Probe Option for Measuring Oil Moisture and Temperature

4.8.4 HMP378F probe option for measuring oil moisture and
temperature
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 (page 71)).
The default HMP378F calculation coecients (see HMP378F calculation model with average oil
coecients (page 117)) are valid for transformer oil. Typically, moisture in transformer oil
measurement with HMP378F has a ppm accuracy of ±10 % of the reading. If required, dierent
oil-specific calculation coecients can be configured into use to customize HMP378F
measurements. For instructions, see Configuring calculation coecients (page 117).
HMP378F uses the HUMICAPâ 180L2 sensor designed specifically for oil and fuel
measurements. For HUMICAP 180L2 sensor specifications, see Table 39 (page 133).
The following measurement parameters are available for HMP378F:
Table 36 HMP378F measurement parameters
Parameter Abbreviation Unit
Temperature T °C (°F)
Relative saturation RS %RS
Water activity a
w
-
Water concentration in oil
1)
H
2
O (oil) ppm
w
1) The default calculation coecients for water concentration in oil (ppm
w
) are valid for
mineral transformer oil. For more information on default and oil-specific calculation
coecients, see HMP378F calculation model with average oil coecients (page 117) and
HMP378F calculation model with oil-specific coecients (page 118).
4.8.5 HMP378H probe option for measuring JET A-1 fuel
moisture and temperature
The HMP378H probe option is a variant of the standard HMP378, designed for measurements
in JET A-1 fuel (typical ppm accuracy: ±15 % of the reading). The mechanics of the probe are
the same as in the standard HMP378 probe option (see HMP378 probe for pressurized
pipelines (page 71)).
HMP378H uses the HUMICAPâ 180L2 sensor designed specifically for oil and fuel
measurements. For HUMICAP 180L2 sensor specifications, see Table 39 (page 133).
The following measurement parameters are available for HMP378H:
Chapter 4 – Probe options
79