Electronics > Beginners
Scope probe to bnc adapter-type panel mount socket.
Greg Robinson:
Hi everyone.
Bit of an odd question, I'll start with some context.
I'm putting together a simple curve tracer to use with my scope. Now, I could make the horizontal and vertical outputs 50 ohms, use BNC connectors and coax and 50 ohm feed through terminators on my scope, but that would mean some extra expense - I don't have any 50 ohm feed throughs (not much use for them until now) so I'd need to purchase those, and I'd also need a circuit capable of driving 50 ohms (100 ohms), which would add significantly to my BOM compared to if I were able to say, drive a 1Meg/10Meg scope probe which any old op amp can manage.
So, my plan is to use regular 10:1 scope probes rather than use coax. All good so far.
Now, I do already have probe tip to BNC adapters, but it got me to wondering if there are purpose built 3.5mm or 5mm panel mount probe sockets? I haven't been successful in my searches, but if they do exist, I'm sure someone here would know, though I would not be at all surprised if they don't.
If they do exist, it would just mean I wouldn't need to dedicate more adapters to a single piece of equipment with the potential for them to go missing, etc.
I also welcome any feedback about my intentions, if my thought process is flawed, please let me know. Thanks again for any help.
tggzzz:
Curve tracers, unlike VNAs, are low frequency and don't need impedance matching. Indeed, that would be impossible since your UUT will have undefined and varying impedance.
The signal source will need to supply whatever current is required by the UUT, so ideally it will have a low output impedance.
You don't want the UUTto be disturbed by the measuring devices, so they need a high input impedance. Usually 1Mohm is high enough, but that will depend on the UUT.
So, to over simplify, the ideal source is a PSU or high current opamp, and the input can be a scope input connected to the UUT by pieces of wire or coax. No 50ohm terminations needed.
Greg Robinson:
Thanks tggzzz, but I'm not talking about the probe from the curve tracer, rather the horizontal and vertical outputs from the curve tracer to the scope.
tggzzz:
So am I. Or isn't the scope part of the curve tracer?
Greg Robinson:
Ok, then I'm completely misunderstanding what you're saying. How on earth would the horizontal and vertical outputs effect the DUT? There'll be mixers/buffers between them. I'd already been planning for the probe input to have a high impedance, and I wasn't asking about that and certainly not suggesting I would make it 50 ohms. I'm very confused.
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