Is this dangerous for my scope/awg? - Page 1
Forum section: electronics / beginners

author: jfharper
author_rank: Contributor
timestamp: March 06, 2025, 03:44:11 pm
content: I need to add a low pass filter to an opamp booster I made and would like to learn my scope and awg more using a bode plot.A youtube commentor wrote this on this video"I tried this a different way. I used a 10 X probe on channel 1 across the resistor, capacitor combination and a 10X probe on channel 2 across the output capacitor. Setting DUT input on channel 1 and the DUT output on channel 2 gives me the same Bode plot as connecting AWG channel 1 to scope channel 1 and DUT output to channel 2. Difference is that I do not have to worry about matching the cable's 50 ohm impedance into the scope and do not have to synchronize channel 1 and channel 2 of the function generator as only one channel is being used."Heres and image of how I think I should setup (I'm not sure I need the USB connection between the awg-scope or need to enable tracking). I don't have any 50ohm terminators and would like to try without waiting for them to ship to me.Can someone confirm this is safe so I don't damage my scope and/or awg?

author: gamalot
author_rank: Super Contributor
timestamp: March 06, 2025, 03:59:48 pm
content: Don't worry at all, it's safe.

author: tggzzz
author_rank: Super Contributor
timestamp: March 06, 2025, 04:10:37 pm
content: That's not a bode plot. Bode plots have logarithmic amplitude and frequency scales, so that simple filter roll offs are straight lines, e.g.Whether that matters for your use case is a separate issue.Apart from that, the 50ohm load doesn't appear necessary....The sig gen's output voltage will be stated presuming a 50ohm load, i.e. a potential divider with the output resistance and load resistance. If the load is open circuit, then the voltage will be double that indicated on the sig gen.Correctly terminated cables become important at high frequencies. "High" depends on the combination of cable length plus frequency (sine waves) or risetime (rectangular/trapezoidal waves). I doubt that is important at 200kHz.

author: TomWinTejas
author_rank: Regular Contributor
timestamp: March 06, 2025, 09:39:26 pm
content: Dave had a video about mismatched impedance causing ringing at higher frequencies and he showed that you can use a 51 ohm resistor in a pinch so long as it's properly rated for the load.With regards to how to interconnect them, I've already got both on my network so I just let them talk via IP.

author: tautech
author_rank: Super Contributor
timestamp: March 09, 2025, 08:54:31 am
content: Quote from: jfharper on March 06, 2025, 03:44:11 pmSee this post for detailed Bode plot/FRA use and configuration of connections:https://www.eevblog.com/forum/testgear/siglent-sds1x04x-e-bodeplot-ii-(sfra)-features-and-testing-(coming)/msg2453661/#msg2453661Siglent DSO's that support Bode plot do certainly require LAN or USB connection between the Siglent Arb and DSO for the scope to take control of the Arb and its amplitude and frequency sweep.While getting the hang of Bode plot you could follow these simple examples:https://www.eevblog.com/forum/testgear/siglent-sds1204x-e-released-for-domestic-markets-in-china/msg1435854/#msg1435854https://www.eevblog.com/forum/testgear/siglent-sds1204x-e-released-for-domestic-markets-in-china/msg1436912/#msg1436912