HMP378F calculation model with average oil coefficients - HMT370EX

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

ppm_w = a_w × 10 ^{(A/(T+273.15)+B)}

a_w

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.