Measurement unit problem on 2206B

michael.farmer · Post by **michael.farmer** » Mon May 25, 2020 11:24 am

I have noticed an apparent discrepancy between a sine wave amplitude displayed in scope view and the corresponding component displayed in spectrum view. If I select a 100mV amplitude signal fixed at 20kHz and connect the AWG port directly to the channel B port (no probe or external attenuation), the scope trace shows 100mV peak (200mV pk to peak) as expected but the 20kHz response on spectrum trace shows an amplitude of -20dBu. I would expect to see -20dBV under these conditions (or better yet -23dBV, this being the value corresponding to the RMS amplitude). My scope is a 2206B running software version 6.13.7.706 on a MacBook Pro. What am I doing wrong, please? And as a final question, what is the effective output impedance (source impedance) of the AEG port?

michael.farmer · Post by **michael.farmer** » Tue May 26, 2020 9:09 am

I think I have partially solved my own problem. If I select the "Y" axis scale window and select "dBV" I get the correct reading but I am a little surprised that the scaling doesn't adjust automatically to match the input signal. Sorry about the typo on AWG but the question about source impedance still stands.

Post by **Martyn** » Tue May 26, 2020 10:52 am

The AWG output impedance is 600 Ω

michael.farmer · Post by **michael.farmer** » Tue Jun 02, 2020 7:59 am

Thank you, Martyn, that's all I needed to know.

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Measurement unit problem on 2206B

Measurement unit problem on 2206B

Re: Measurement unit problem on 2206B

Re: Measurement unit problem on 2206B

Re: Measurement unit problem on 2206B