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# CN0510 - AD5941BATZ: Measure of a known resistance

Category: Hardware

Hi,

me and  are trying to measure the impedance of a known resistor (220 Ohm) with the AD5941BATZ, using the example code of impedance measurement, but we're getting measurements that are not consistent with the resistor impedance value. Do you know why it doesn't work?

• Can you provide a sketch for how you've hooked up the resistor? (A photograph is also often helpful.) What measurement values are you reading back? Are they off by some "reasonable" tolerance (10%, even 20%), or do they vary wildly? Are you biasing it to some voltage, or simply connecting it across the input terminals? The CN0510 current sink requires some compliance voltage.

this seems to be a common question - do we have any documentation on how to test the CN0510 with a benchtop power supply and fixed resistors? If not, it would be a good idea to add this to the wiki page (which only shows testing with an actual battery)

-Mark

• Hi,

Note that the ADC of AD5941 can take voltages only within the range

1) 0.2V to 2.1V on each pin

2) Within +/-0.9V differential voltage for ADC PGA gain = 1 or 1.5,

within +/-0.6V differential voltage for ADC PGA gain=2,

within +/-0.3V differential voltage for ADC PGA gain =4,

within +/-1.33V differential voltage for ADC PGA gain =9.

If voltage values are beyond this range, result will be erratic due to saturation.

If may check these voltages at AIN2, AIN3 and across AIN2 and AIN3 pins on AD5941BATZ board and verify.

• Sorry. We’re using the example code of battery impedance measurement to measure a resistor of 220 Ohm.

• Yes. Since you are using the example code of battery impedance measurement to measure a resistor of 220 Ohm, you may check these voltages at AIN2, AIN3 and across AIN2 and AIN3 pins on AD5941BATZ board and verify if they are within allowed range.