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Single frequency test on CN0510/AD5940 issue

Hi, I've using CN0510 battery impedance measuring board, and it works fine with correct battery holder.

When I measure the impedance using sweep frequency function (like sweep the frequency from 1 to 10kHz), the result is fine. 

But if I test the specific frequency, the impedance is not as precise as using sweep method.

Also, when I using frequency larger then 3kHz, the measurement data is useless, since the RCAL voltage is wrong.

I check AIN1 point at CN0510, the excitation signal is correct as using sweep function.

 

The console result is like below:

** Set frequency to 3792.68Hz
Hello AD5940-Build Time:20:48:12
This AD594x!
Note: Current Silicon is S2
AD5940LIB Version:v0.2.1
RcalVolt:(2.000000,0.000000)
Fix frequency : 3792.689941
Test condition, AC Vpp: 300.00 mV, DC bias: 3200.00 mV
Freq: 3792.689941 (real, image) = ,0.000000 , -25.000000 ,mOhm
Freq: 3792.689941 (real, image) = ,0.000000 , -25.000000 ,mOhm
Freq: 3792.689941 (real, image) = ,25.000000 , -25.000000 ,mOhm

** Change frequency to 1438.44Hz **
Hello AD5940-Build Time:20:50:42
This AD594x!
Note: Current Silicon is S2
AD5940LIB Version:v0.2.1
RcalVolt:(-37.000000,33.000000)
Fix frequency : 1438.448975
Test condition, AC Vpp: 300.00 mV, DC bias: 3200.00 mV
Freq: 1438.448975 (real, image) = ,11.391376 , -0.650936 ,mOhm
Freq: 1438.448975 (real, image) = ,11.391376 , -0.650936 ,mOhm
Freq: 1438.448975 (real, image) = ,11.391376 , -0.650936 ,mOhm

So, the sweep measurement is good, but single frequency test is failed, I'm wondering why this happened?

I want to test the specific point in EIS so that I can get the optimize frequency faster.

Thanks all of your help!

Have a nice day

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  • Thanks for your reply, but even I set bias to 1200mV, the single frequency test also lost accuracy in some specific value. 

    The experiment result is like below:

    The Y axis is impedance, X axis is frequency.

    Reduce bias can fix accuracy at most frequency, but at 1128Hz, 2335Hz the impedance is not as same as frequency sweep method.

    Also, at high frequency (<500kHz) region, the data is not useable so they are not plot in the figure.

    Is there something like build-in filter is not setup correctly?

  • Apologies for the slow reply. I have just pushed some updates to the repository. There was indeed a bug in the code that did not set the ADC filters properly when a sweep was not enabled. See line 423 in the BATImpedance.c file for updates.