REW Beta Release Calibrating impedance measurements

[Vladimir123]

Lets start from the diagram at the start of Impedance Measurement topic in the REW help. First step - open circuit calibration. As far as I understand, the diagram change is to short the sence resistor and disconnect two wires (test leads) from the driver, so the inputs L and R of soundcard are connected together and both measure the voltage from the power amplifier (in my case it is Gryphon Diablo). The second step - short sircuit calibration. The short from the sence resistor must be removed and test leads instead of the driver are connected to each other. So left input of the soundcard measures the voltage from amplifier and the right input measures the voltage across the impedance of the test leads. The third step - reference resistor calibration. The test leads are connected to the reference resistor and sence resistor is not shorted. So the left input measures the voltage from amplifier and the right input measures the output voltage of the voltage divider made of sence and reference resistors. AM I rigth?

 

[John Mulcahy]

No. Do not short the sense resistor at any time. The open circuit measurement means what it says, make a measurement with the leads open, nothing else changes.

 

[Vladimir123]

Would you please provide some examples of the typical graphs of all three measurements. Maybe some comments. I have some difficulties understanding what they show. Thank you in advance.

 

[John Mulcahy]

The open circuit graph shows relative gain of the input channels. The others show the measured impedance.