2021-10-21 09:31 AM
Hi,
So I got myself an EVALSTPM34 and decided to test it out with the evaluation software given by ST.
According to the STPM34 datasheet/user manual to read the primary channel current and voltage I have to read the 48th register which contains the data in the following format:
And the LSB values as per the manual in evaluation boars are
Now with this information in hand if I read the voltage/current using the software I get the following
48th Register value: FFFFDAD3
Voltage displayed by software: 142.8
Current displayed by software: 0.93
The values match the actual input to the board. However if we do a calculation according the user manual for the above register value I end up with
voltage: dec( 0x5AD3)*0.036= 837.06
Current : dec (0x1FFFF) * 0.00027 = 35.38
Why is there a discrepancy between the displayed value and the value I calculate according to the user manual?
Some other example values of register 48 for same inputs are:
00000D7A
FFFFDA5E
00000D7A
FFFFDEA8
My source is precise and does not have any variations yet the register values seem to go all over the place.
I am stumped and need some fresh eyes to let me know what I am wrong.
Appreciate your help! Thanks!