Vaisala HMT370EX - HMP378 F Calculation Model with Oil-Specific Coefficients

Typically, moisture in transformer oil measurement with HMP378F has a ppm accuracy of
±10 % of the reading. If additional accuracy is needed, see HMP378F calculation model with oil-
specific coecients (page 118).
9.4.2 HMP378F calculation model with oil-specific coecients
For additional accuracy, an oil-specific calculation model can be used in HMP378F for mineral
transformer oils. A specific model is always needed for other transformer oil/fluid types. Note
that the calculation is only supported for stable dielectric fluids.
For oil-specific coecients, an oil sample has to be sent to Vaisala for modeling. As a result,
the specific coecients (A and B: see formula in HMP378F calculation model with average oil
coecients (page 117)) for the oil are determined by Vaisala. Using these coecients increases
measurement accuracy.
You can configure the determined coecients of the oil into use with Insight PC software, or
contact Vaisala about setting the coecients. For configuration instructions, see Configuring
calculation coecients (page 117).
HMT370EX User Guide M212305EN-B
118