Hello all
I have a question about the sensitivity and stability about the impendance measurement of using the LDC1000 EVM.
Since I need to obtain a precise measurement of the impendance, I set the RpMin 9.25 kOhm and RpMaX 16.16kOhm in order to get a higher resolution this measurement. Resonance frequency is 6kHz. The frequency count setting is 192. voltage 4v.
Also, I have changed to original filter capacitor into a 3.3uF one , whcih gives a voltage about 600mV on the CFB pin with my settings.
The test is carried out by placing my probe at a fixed poistion on the sample. Then I run the test for 20 times (each time I will used the Matlab to collect data and also the bad data will be filter out by digital filter designed in Matlab)
The measurment on the inductance is very accurate but it is not the case for the Impendacne.
For example, I list the measurement of the impendance result as followed.
Test starts
test 1; 12.95196 kOhm
test 2; 12.95349 kOhm
test 3; 12.94662 kOhm
test 4; 12.94618 kOhm
test 5; 12.94465 kOhm
Stop for 1 min, then restart the test.
test 6; 12.95528 kOhm
test 7; 12.95041 kOhm
test 8; 12.94996 kOhm
test 9; 12.94406 kOhm
test 10; 12.94131 kOhm
Stop again, wait for 5 min, then restart the test.
test 11; 12.92854 kOhm
test 12; 12.93317 kOhm
test 13; 12.93353 kOhm
test 14; 12.93079 kOhm
test 15; 12.92880 kOhm
test 16; 12.92445 kOhm
test 17; 12.92105 kOhm
test 18; 12.91708 kOhm
test 19; 12.91755 kOhm
test 20; 12.92028 kOhm
In addition, each test has a very low standard deviation (STD) of about 0.002 kOhm, which means that each test result is quite reliable.
However, as you can see in the mean value listed above, the Rp FLUCTUATE a lot compared to the STD mentioned just now.
So, in you guys's opinion, what is the possible reason for this behavior and any suggestion to improve the performance of the probe.
Thank you very much!
