fra not giving exact result

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tauquir

10 Sep 2022
Posts: 1

i have two 47 ohm resistance in series. say pin1 R of R1- pin 2 of R1 connected to pin 1 of R2 and then pin 2 of R2.
when i connect signal generator and channel 1 to pin 1 of R1 and pin 2 of R2 as said in the document. and channel 2 to the pin 2 of R1 or pin 1 of R2. i am getting resistance of 33 ohm

bartschroder

12 Sep 2022
Posts: 471

Hi,
It sounds like you are using Circuit A.

Make sure the Coax Termination is set to Open, and R ref is set to 47.

Please check, and let us know what you find. If you do a File/Save As.. and send us the .apc of your setup, we can check it, and make sure it is ok. Use support@cleverscope.com.

bartschroder

13 Sep 2022
Posts: 471

Hi,
there is also another possibility.
If you have the Amplitude/Power in dB led turned on (top right of FRA control panel), the result will be in dBOhms. The reference is set in Settings/Analog Names and Units, and defaults to 1.

20 x log(47/1) = 33.4 Ohms. So perhaps you had this turned on. If so, the amplitude axis would have been in dBOhm.

Bart

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