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| "Trigger box" for advanced/complex scope triggering? |
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| meretrix:
--- Quote from: rhb on December 05, 2018, 03:45:11 am ---I'm a little surprised a LeCroy wouldn't do what you wanted, but likely it's an option. However, rather than try to capture this on a scope, it seems to me more appropriate to deliberately create worst case conditions, abuse a relay for a large number of cycles and then examine the contacts. Also for this case a spectrum analyzer would tell you if it were arcing. --- End quote --- Yeah, that was another part of the test. The 180° out of phase 277VAC supplies switching at peak was one part, and then it repeated itself every 30s or so for an hour. No arcing, not even damage to the fusible resistor. One theory out the window... |
| boB:
I have needed something like this on and off once in a while for many years. Thought about making a trigger box too a few times. Never did except for a couple times with very simple external combining of filtering or whatever. Can't even remember now. Sometimes you're debugging a circuit and a condition comes up so rarely but you just need to catch it and usually multiple channels are needed for trigger. At least in my work. Usually it's just some combination of logic of pulse conditions that need to be triggered from more than one channel. My Rigol and Pico Scope have pretty advanced trigger functions but every once in a while I wish I had another way to trigger. One of our older Rigol scopes with pulse trigger had/has a bug in one of the modes. I think the newer scopes work though. |
| David Hess:
In the past I have used a word recognizer as part of a solution to do this. Several analog signal conditioning circuits drive the word recognizer which is configured by the oscilloscope to trigger on a specific set of inputs. A modern implementation would use the oscilloscope's logic analyser inputs in place of the external word recognizer. |
| rhb:
For use with a scope that lacks an LA, the pod set from one that does feeding a small FPGA would do quite nicely. A cheap Zynq or Cyclone V dev board with USB and ethernet would be especially easy to setup with the desired trigger conditions. The GW Instek GTL-16E pods are a set of adjustable reference levels and ADCMP581 comparators with input buffers to withstand +- 40 V and output line drivers. I'm sure all of the decent ones are some variant of that. The connector that plugs into the MSO-2000E is just a connector. All the electronics are in the pods. They seem over priced until you lookup the parts on Digikey. The 180 pS delay doesn't come cheap. The Digilent Discovery line are just bare 3.3 V FPGA pins without any protection. I think that a rather cruel prank to play on a novice. |
| meretrix:
--- Quote from: boB on December 05, 2018, 06:02:02 am ---My Rigol and Pico Scope have pretty advanced trigger functions but every once in a while I wish I had another way to trigger. One of our older Rigol scopes with pulse trigger had/has a bug in one of the modes. I think the newer scopes work though. --- End quote --- Heh, I tried to get the guy in charge of purchasing to get one of the higher-end Rigol scopes, but he was adamantly opposed to getting a scope from any company he didn't know about, so it had to be either Agilent, Tektronix or Lecroy. Joke's on him cos we could have gotten a much more powerful and flexible scope for the same amount of money... except, as it turns out, the joke is actually on me because I'm the one who ends up using the thing most often. :-\ |
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