EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: cncjerry on November 18, 2017, 01:16:33 am
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So I have two HP probes that came in a nice plastic box will all the adapters, etc and pods for use in an HP scope. I use them in a 5371A TIA. They are really nice, all kinds of adapters, etc, very small, easy to use in tight places.
Setting aside the pod, can you use these on a Tek scope? TDS744 or TDS3054C? I realize the Tek won't recognize them. Any drawbacks?
thanks
Jerry
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Which probes are we talking? HP used to make these little external power bricks for scope probes, you can often find them on eBay. If you're using one of those it doesn't really matter much which scope you're using in most cases. Just keep in mind what the output of the probe actually means! But yeah, it's certainly possible for some probes, I commonly use HP current probes on a Tek scope.
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If they are standard 10:1 probes be aware that the compensation adjustment range that the probe covers must match the scope input capacitance. So, if your scope has a 10 pF input capacitance and the probe is spec'd for 15-30 pF you will have problems.
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If they are standard 10:1 probes be aware that the compensation adjustment range that the probe covers must match the scope input capacitance. So, if your scope has a 10 pF input capacitance and the probe is spec'd for 15-30 pF you will have problems.
1. If the compensation adjustment range doesn't match does that mean even if a probe is adjusted with a scope's square wave calibrator that the combination of probe and scope won't work accurately?
2. Does this mean that a probe that works on Tektronix 22XX with 20pF inputs might not work accurately on a Tektronix 24XX with 15pF inputs?
3. I noticed that a Tektronix P6137 probe has a spec of 10.8pF and it is marked as suitable for a "2400" scope, but the inputs on a 2467B say 15pF. Does this mean that as long as the probe is spec'd at less pF than the scope input the probe should work ok? So for example, the P6137 should work with a 22XX as well as a 24XX?
Thanks
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I am referring to HP 54003A probes. I'll have to take a look at the cap and impedance. These things have more adapters than any I've ever seen.
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Setting aside the pod, can you use these on a Tek scope? TDS744 or TDS3054C? I realize the Tek won't recognize them. Any drawbacks?
The frequency response beyond 200 MHz or so will likely be less accurate because high-impedance passive probes will have been specifically designed to the (not very flat) input impedance of the scope front-end. This is why Tektronix used to make the pretty similar P6131, P6134, P6136, P6137, P6138a and P6139a: to match the different front-ends used in various of the high-bandwidth scopes. After that, they started to use one common front-end design, which is why the P6139a was recommended for most newer digital scopes. See here (https://groups.io/g/TekScopes/message/106275) for a more detailed explanation by an ex-Tektronix employee.
1. If the compensation adjustment range doesn't match does that mean even if a probe is adjusted with a scope's square wave calibrator that the combination of probe and scope won't work accurately?
If the compensation adjustment range does not match, you will not be able to compensate the probe for a good square wave response from the probe compensation output.
2. Does this mean that a probe that works on Tektronix 22XX with 20pF inputs might not work accurately on a Tektronix 24XX with 15pF inputs?
Yes, it may not compensate properly. That said, these trimmers are not know for particularly tight tolerances. I have gotten Tek P6137s to compensate on nominally 20 pF input scopes. But obviously it is not guaranteed.
3. I noticed that a Tektronix P6137 probe has a spec of 10.8pF and it is marked as suitable for a "2400" scope, but the inputs on a 2467B say 15pF. Does this mean that as long as the probe is spec'd at less pF than the scope input the probe should work ok? So for example, the P6137 should work with a 22XX as well as a 24XX?
Look at the compensation range, not the probe input capacitance. The P6137 is specced (https://www.valuetronics.com/pub/media/vti/datasheets/Tektronix%20P6131,%20P6137,%20P6138A.pdf) as compensating to scopes with an input capacitance of 12 to 18 pF.