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Triggering scope with foot pedal switch
slugrustle:
Thanks for that. Turns out my local copy of the datasheet is one rev older and doesn't have that info. It's good to know.
I'm pretty sure the 1M/50Ω different for the "Ext Trigger Channel input voltage" line has to do with the EXT channel input impedance, not the source impedance.
In any case, the circuit I'm building runs from a 9VDC source, has slightly under 5V output voltage unloaded, about 50Ω output impedance, and the overvoltage crowbar should trip at around 6V, but only if there is some kind of fault condition.
I'll keep the EXT input impedance at 1MΩ though based on this info from the datasheet; the extra headroom shouldn't hurt.
tautech:
--- Quote from: slugrustle on July 29, 2023, 01:55:04 am ---I'm pretty sure the 1M/50Ω different for the "Ext Trigger Channel input voltage" line has to do with the EXT channel input impedance, not the source impedance.
--- End quote ---
From datasheet:
Ext Trigger Channel input voltage 1 MΩ ≤ 42 Vpk, 50 Ω ≤ 5 Vrms
To me seems very clear this ^ indicates source impedance.
Therefore a series resistor in the source of your switching output can keep the signal within limits without need of a crowbar.
BTW, threshold levels that you set when selecting Ext Trig:
EXT: ±0.61 V
EXT/5: ±3.05 V
slugrustle:
Max input voltage for the other channels, the normal scope channels, is listed as
1 MΩ ≤400 Vpk(DC + AC), DC~10 kHz
50 Ω ≤5 Vrms, ±10 V Peak
Do you think 1MΩ and 50Ω for the normal input channels represents the output impedance of an external source? I'm pretty sure it's the channel input impedance on the scope. The same 5V limit applies to normal input channels and to the EXT channel at 50Ω, presumably due to a power limitation.
Perhaps you mean something different than I do by source.
The scope can set the input impedance of the normal channels and of the EXT channel to 1MΩ or 50Ω, and the input voltage limits are listed for both input impedance settings. It would be really weird for the scope to be able to set its inputs to these two specific impedance values, list max voltage limits according to these two impedance values, and then intend the impedance values to refer to the output impedance of some external source...
jmw:
--- Quote from: dobsonr741 on July 11, 2023, 02:10:14 am ---Food for thought: voice assistant triggering single shot trigger over SCPI.
--- End quote ---
https://github.com/jmwilson/ollie
Snips is gone, but it's an offline voice assistant, so the image will continue to work indefinitely.
Psi:
If I was going to do that I'd probably have a switch mounted on the underside of the desk where I can press it with my knee.
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