HMP378F calculation model with average oil coefficients - HMT370EX

HMT370EX User Guide

Document code
M212305EN
Revision
B
Language
English
Product
HMT370EX
Document type
User guide

The oil moisture calculation model in HMP378F probes is based on average water solubility behavior of transformer oils. The ppmw output is calculated as follows:

ppmw = aw × 10 (A/(T+273.15)+B)

aw
water activity
A, B
coefficients (average or oil specific)
T
temperature (°C)

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 coefficients.