Quick question, look at the attached circuit. At 500 Hz the calculated impedance phase is -88.2 but when you measure across R1 (channel B) in comparison to the input (channel A) you read 88.2. Why is the measured reading 180 out? Any help would be appreciated.

Thanks,

Tony D.

 

Tony

Is the oscilloscope triggering off A or B Channel ?

 

You are not measuring impedance, but you are measuring voltage at a point. Use the voltage divider rule and you'll see the total series impedance is in the denominator. Do out the math and you'll see the oscope is correct.

Also, note that you are not a full 180 deg out from what you expect. It's actually 176.4 deg.