STPM33/34 shows current 60x lower than real

[Afra_mabrouk]

Hi,
I have a working 3-phase STPM33/34 energy meter. Voltage is correct. The current is wrong by a fixed factor of approximately 60.
Setup:

CT: 80A primary / 5A secondary
Burden resistor: 6.8 Ω
Gain: x2
Mode: UART with auto-latch
Expected reading: 0.6A → Actual reading: 0.01A

Why I think this is a calibration/formula issue and not a hardware fault:

The error is consistent and proportional (not random)
Voltage on same chip reads correctly
CRC passes on every frame
No register corruption detected
My question to the community:
Has anyone seen a x60 error factor on STPM33/34 current channels? Which misconfigured parameter — CT ratio in firmware, KI calibration register, Kint constant, or gain setting — would produce exactly this ratio?

[Didier HERROUIN · Accepted solution]

Dear Afra_mabrouk,

It could be a calculation (the gain is part of the formula) or a CT ratio error (a calibration error can not generate such a high error).

Please provide the reference of your CT (you provided the burden resistor but not the number of turns).
Also, please join the values of your registers (configuration and data) so that I could check the calculation.
You can also use the excel file attached (tabulation “Data registers calculation”) to check your own calculations.

Best regards,

Didier Herrouin 

[Afra_mabrouk]

Thank you for your response.

I confirm that the issue has been resolved. It turned out that the problem was indeed related to the CT ratio, as you mentioned.

I appreciate your support.

[Didier HERROUIN]

Thanks for your quick and positive feedback !