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Hello,
I'm trying to use an INA780 for measuring charge, and although I'm capable of correctly measuring current, when converting the charge register value, the result doesn't match the expected.
According to Table 7-4 present on the device datasheet, the LSB value of the charge register equals to 150uC. Also on the same table, the example shown doesn't appear to be correct. Considering LSB = 150uC, and a register value of 13500000d, the expected charge value would be 2025000C, however, the result shown in the "Calculated Value" column doesn't match.
After comparing the obtained results with the expected ones, it was discovered that the obtained value was 2.4 times larger than the expected.
I would be grateful for any help regarding this issues.
Best regards,
André Costa
Hello Appreciated Engineer,
I am looking this over and will respond shortly.
Best,
Peter
Hey André,
Would please show me how you obtaining the 2.4x value? Specifically, what you read from charge register and the subsequent calculations? Also, how are you calculating the true charge value?
The table you mentioned does have an error. For the Charge row, the "RETURNED VALUE" cells should read: "216000000d, CDFE600h". These equate to 32,400 C with the 150uC LSB. The charge should be 32,400C because it equals energy/voltage (1.552MJ/48V). To clarify, these values in the table are the converted 1's complement. You will need to first convert Charge register contents from 2's complement to 1's complement.
Sincerely,
Peter