Measuring 6 cells of a battery pack with CN0510 by multiplexing

Hi,

  Excitation can be given at the main terminals alone.

  The AC potential across each battery is measured by ADC of AD5941.

  If this potential is very small or very big (outside allowed voltage input range of ADC), results will be erratic due to ADC saturation.

  You may adjust the gain of input potential

- by opamp stages or bypassing them as shown in CN0510 schematic below:

or by changing ADC PGA gain and RTIA values inside device via code.

Hello Akila,

Thank you for your answer. There is an example measurement on one of the series of my battery pack. when I connect all the cables on the first series the result looks expected and it is consistent, but when I connect the F cables on the main terminals of the battery pack the results is as you see in the graph, it drifts from the reference measurement a lot. I have already checked that AIN2 and AIN3 (from the R17 and R20) signals are within +900mV -900mV. How can i make this result better? What should i modify on CN0510? What could be the reason of this deviation? (the example measurement is performed on cn0510 with the parameters of DC Bias: 1200mV, AC amplitude: 600mV, Frequency: 1Hz-1kHz, Points: 30)

Thank you.

Akila  Can you help about this?

Hi,

 Could you please show your connection with block diagram for clarity?

Here is my connection diagram. Currently Im just using CN0510 and switching the cables manually by hand.

Here is my connection diagram. Currently Im just using CN0510 and switching the cables manually by hand.

The difference between the two configurations is that

- AC current excitation appears across a larger impedance in T2T case versus smaller impedance in differential case.

   There could be deviation from Ohms law in 1st case due to non-linearity at higher impedance.

- EXC_P(see CN0510 schematic) DC value is changed

Behavior of T1B31BG (Darlington pair) in CN0510:

You may change the DC Bias for each case and check.