Vaisala HMP228 User's Guide download pdf (Page 33)

Chapter 4 _________________________________________ MENU OPERATIONS AND SETTINGS

If additional accuracy is needed, more information is found below in

the section Calculation Model with Oil Specific Coefficients on page

31.

Calculation Model with Oil Specific

Coefficients

For additional accuracy, oil specific calculation model can be used

both for mineral and silicon based oils. An oil sample has to be sent to

Vaisala for modelling. As a result, the specific coefficients (A and B,

see formula above) for the transformer oil are determined by Vaisala.

Using these coefficients the accuracy of measurements is increased.

The determination of specific coefficients shall be agreed with the

Vaisala representative.

The determined coefficients of the transformer oil can be programmed

to the MM70 by Vaisala or by a user according to the following

instructions.

NOTE

Calculation Model with Oil Specific Coefficients is always needed

for silicone based oils.

Feeding the Coefficients to the

MI70 Memory

You can save in the memory specific coefficients for 4 different oils.

As shipped from factory the average coefficients are set for the

number 1 type (H2O oil: 1). Add your own coefficients as follows:

1. Open the MENU. First press the right arrow key, then press the

OPEN key.

2. Select Settings and press the right arrow key.

3. Select Measurement Settings and press the right arrow key.

4. If you want to keep the average coefficients under identification

number 1 (set in the factory), press the SET key and key in

number for the second oil type.

5. Select the A value (A:0.0000) and press the SET key.

6. Set the value A by using the arrow keys up/down/left/right,

press the OK key.

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Vaisala HMP228 User's Guide Page 33