Vaisala HUMICAP MMT162 Guia do Utilizador descarregar pdf (Página 48)

User's Guide _______________________________________________________________________

46 ___________________________________________________________________ M210934EN-D

ppm Conversion

MMT162 ppm Conversion for

Transformer Oils

Traditionally, moisture in transformer oil is measured by using ppm

units. The ppm output shows the average mass concentration of water in

oil.

The moisture and temperature transmitter MMT162 has an option for

ppm-output provided that this has been notified when placing the order

for the transmitter. Vaisala has this conversion readily available for

mineral transformer oils.

Conversion Model with Average

Coefficients

The conversion model of the MMT162 is based on the average water

solubility behaviour of transformer oils. The ppm-output is calculated as

follows:

ppm = aw×10

(A/(T+273.16)+B)

where

water activity

A,B

coefficients (average/oil-specific)

temperature (ºC)

Generally, measurements with MMT162 give accuracy better than 10 %

of the reading. If additional accuracy is needed, refer to section

Conversion Model with Oil-specific Coefficients below.

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Vaisala HUMICAP MMT162 Guia do Utilizador Página 48