Z_Logger: Erroneous Z Values

Question

Z_Logger: Erroneous Z Values

Closed this issue 10 years ago · 5 comments

I spoke too soon about Z_Logger working consistently. When no load is placed across Vin and Vout (pins 5 &6), the impedance increases dramatically (as expected). However, when I try another resistor (e.g 10K, 1K), I get results near the calibration resistor value. I'll add some checks on the measurements after the gain factor calculation.

Answer 1 · 2014-08-05T20:49:21.000Z

I think your program measure the impedance as soon as get the gain factor without changing resistors. Did you let the program prompt to change the resistor? Otherwise, you need to put the "Gain Factor" manually each time.

Answer 2 · 2014-08-05T20:52:20.000Z

Also, did you put the Feedback resistance between pin 4 and 5? You need to read the datasheet.

Answer 3 · 2014-08-05T21:15:18.000Z

Actually, I do not recommend to store and input the gain factor manually because it differs by the atmosphere temperature.

Answer 4 · 2014-08-05T21:18:23.000Z

I suspect the reason is the current between V_in and V_out is saturated to distinguish the difference. The feedback resistor is important in that matter.

Answer 5 · 2014-08-05T21:21:34.000Z

Refer AN-1252 (application note by Analog Inc.) to get the formula to calculate the proper feedback resistor and calibration resistor.