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| Why is my oscilloscope showing a signal? |
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| nigelwright7557:
I did some work on an electronic dog flap, like a cat flap but bigger. The door output a pulse and the collar had a LC on it that rang back if close enough. I found after lunch every day the circuit got swamped with about 15KHz signal. Turned out next door turned their TV on about that time and the TV line oscillator ran at that speed ! Spent a good couple of hours tracking down oscillation in a power amp. Turned out to be my desktop lamp had a CFL lamp in it that radiated badly. Used to work on modems in the 1980's and one day the modem oscillated instead of just amplifying signals. Someone had put the sig gen on top of the scope and it interfered with the scope. Had trouble with 50Hz in a power amp. Turned out my amplifier testbed was poorly laid out with the transformer beneath the amplifier. The magnetic field of the transformer got into the power amp pcb. |
| rf-loop:
--- Quote from: hermitengineer on November 18, 2019, 06:19:46 pm --- --- Quote from: StillTrying on November 17, 2019, 09:16:47 pm ---With only 2.5 samples per division and in dots mode, and going by its large amplitude for that high a frequency, is that 84MHz real or could it just be an aliasing effect. :-\ ...I'm going for aliasing. :popcorn: --- End quote --- It may even be half that. Isn't the 500Ms/s divided between the two channels? If so, each trace gets 1.25 samples per division. Or does the scope sample one trace on each pass and alternate between them? I remember old analog scopes that did that. --- End quote --- No. There is not "may be" things. There is facts how it works exactly. Siglent 1GSa/s ADC is divided to Ch1 and 2. Also as can see in image it display sampling rate and it is 500MSa/s. (and IF it is 4 channel model it have two 1GSa/s ADC's, one for CH1+2 and other for Ch3+4 and these models can run 2 channels simutaneously, both using 1GSa/s. For make this possible user need select ch1 OR 2 AND ch3 OR 4 for use) |
| StillTrying:
--- Quote from: hamster_nz on November 21, 2019, 03:58:14 am ---Last time I had something like this it was a "Baby Monitor" on the other side of the wall, in the room next door. --- End quote --- I'd bet it wasn't 5Vpp. What did the 84.11MHz @ 5Vpp turn out to be. :-// |
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