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| UNI-T UT-P06 300Mhz passive Probes. Are they any good? |
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| battlecoder:
--- Quote from: KungFuJosh on October 07, 2023, 10:24:17 pm ---Like I said, you're not lacking probes. 😉 --- End quote --- I mean... I also like to keep them compensated (and color coded) to the channels of the scope I use them with. I don't normally switch probes around even on the same device. The only probe that was not strictly associated to a scope/channel was the 350 Mhz probe. But yes, true, It's not like I would struggle to find a probe (or an oscilloscope) here. |
| Performa01:
--- Quote from: battlecoder on October 07, 2023, 04:33:08 pm ---Thanks for the detailed response. This is my first dive into the depths of probe performance, so all of the information you've shared and detailed comparisons are extremely useful to me. I think the Texas 250 Mhz probes have two adjustable capacitors, so I assume they are for LF and HF adjustment. Would that be a better option if I were to pick a set of probes that can eventually work with other scopes? --- End quote --- Yes. Like I said, matching a random probe with a random scope is sort of a gamble. Having a user adjustable HF compensation helps a lot in this regard, but still cannot guarantee perfectly flawless performance, as my test with the TesTec TT-MF312 has demonstrated. Furthermore I wanted to remind you on another problem - it's not the probe, but the probing. For all my tests, I have used a probe-coax adapter, connected to a 25 ohms source, which does not even remotely resemble the normal use case. In practice you might have higher impedance nodes and you use the supplied ground leads. This way you cannot get any meaningful results at high frequencies anyway, see reply #62 here: https://www.eevblog.com/forum/testgear/siglent-sds1104x-e-in-depth-review/msg1435196/#msg1435196 Look at the awful pulse responses - any pulse measurements the scope might have will be meaningless with heavily distorted signals like this. To cut a long story short, as long as you are not measuring low impedance nodes and stick to short ground springs instead of the crocodile clips, probe quality doesn't matter and resuls above some 30 MHz will be just visual indicators, but not measurements. And do not forget, this is valid for sine waves only. Even a 1 MHz square wave with short rise time will be distorted, because its harmonics might extend up to several hundred MHz. |
| battlecoder:
--- Quote from: Performa01 on October 08, 2023, 09:24:55 am --- --- Quote from: battlecoder on October 07, 2023, 04:33:08 pm ---Thanks for the detailed response. This is my first dive into the depths of probe performance, so all of the information you've shared and detailed comparisons are extremely useful to me. I think the Texas 250 Mhz probes have two adjustable capacitors, so I assume they are for LF and HF adjustment. Would that be a better option if I were to pick a set of probes that can eventually work with other scopes? --- End quote --- Yes. Like I said, matching a random probe with a random scope is sort of a gamble. Having a user adjustable HF compensation helps a lot in this regard, but still cannot guarantee perfectly flawless performance, as my test with the TesTec TT-MF312 has demonstrated. Furthermore I wanted to remind you on another problem - it's not the probe, but the probing. For all my tests, I have used a probe-coax adapter, connected to a 25 ohms source, which does not even remotely resemble the normal use case. In practice you might have higher impedance nodes and you use the supplied ground leads. This way you cannot get any meaningful results at high frequencies anyway, see reply #62 here: https://www.eevblog.com/forum/testgear/siglent-sds1104x-e-in-depth-review/msg1435196/#msg1435196 Look at the awful pulse responses - any pulse measurements the scope might have will be meaningless with heavily distorted signals like this. To cut a long story short, as long as you are not measuring low impedance nodes and stick to short ground springs instead of the crocodile clips, probe quality doesn't matter and resuls above some 30 MHz will be just visual indicators, but not measurements. And do not forget, this is valid for sine waves only. Even a 1 MHz square wave with short rise time will be distorted, because its harmonics might extend up to several hundred MHz. --- End quote --- Thanks again for the incredibly insightful response. I've been made extremely aware of how probing at "high" frequencies is problematic during the last several days, due to this very same thread. In fact, I don't quite remember how I originally measured that the probes were limiting my bandwidth (the reason I started looking for >250Mhz probes), but I'm 99% sure it was due to bad probing, as I later did a proper bandwidth test with a probe-bnc adapter and a 25 ohms source that confirmed that the probes were pretty OK up to the whole oscilloscope bandwidth. As you say, "proper" bandwidth checks are done in conditions that are far from normal circuit probing, though, so that's also something to keep in mind. |
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