Single frequency test on CN0510/AD5940 issue

HabonRoof on Oct 28, 2021

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

Top Replies

JellenieR
Dec 6, 2021 +1
Hi,

Apologies for missing this item, however I think we can move this to (+) Q&A - Reference Circuits - EngineerZone (analog.com) so someone there can be better assist you.

Thanks,

Jellenie
MLambe
Dec 9, 2021 +1
Hi,

Reduce DC bias to something like 1200mV. This is the DC bias used by the excitation and measurement circuit that is set by the AD5941.
MLambe
Dec 23, 2021 in reply to HabonRoof +1 verified
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…

0 andreialejandro

on Oct 29, 2021 8:00 AM
Hi,

We will look into this, I'll contact the product owner and get back to you.

Regards,

Andrei
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0 JellenieR

on Dec 6, 2021 8:33 AM
Hi,

Apologies for missing this item, however I think we can move this to (+) Q&A - Reference Circuits - EngineerZone (analog.com) so someone there can be better assist you.

Thanks,

Jellenie
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0 MLambe

on Dec 9, 2021 8:51 AM
Hi,

Reduce DC bias to something like 1200mV. This is the DC bias used by the excitation and measurement circuit that is set by the AD5941.
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0 HabonRoof on Dec 15, 2021 11:14 AM in reply to MLambe

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?
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+1 MLambe

on Dec 23, 2021 11:04 AM in reply to HabonRoof
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.
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