Use of Oscilloscope Probe x100 Vs x1000 - Page 1
Forum section: electronics / testgear

author: 2X
author_rank: Frequent Contributor
timestamp: April 03, 2024, 09:12:58 pm
content: Hello,I want to buy one of the below oscilloscope probes in order to measure 230Vac and the output voltage of backlight inverter for driving CCFL lamps (~1000Vrms) but I am little confused when I am looking their specs.I beileived that the difference between x100 Vs x1000 probe is that with x1000 probe can be measured higher voltages in respect with x100 probe, but on the specifications (page 7) of the two below probes the probes rating voltages are same. So, what is the purpose of the x1000 probe?x100 probeR&S®RT-ZH101409.7720.02x1000 probeR&S®RT-ZH111409.7737.02

author: DaneLaw
author_rank: Frequent Contributor
timestamp: April 03, 2024, 11:58:23 pm
content: Why have you singled out these two x100 & x1000 probes from R&S?Im not familiar with them, just briefly looked them up. they both seem to be 400MHz X100 (ZH10) around 740$ and the X1000 (ZH11) around 1300$ [Farnell, though incl. VAT.]

author: Psi
author_rank: Super Contributor
timestamp: April 04, 2024, 01:12:24 am
content: There's a few things to consider with high voltages and probes.There is the x10 x100 x1000 etc. Which controls what voltage the scope input will see, and source loading.If your scope input can handle 200V peak to peak then using a x10 probe means you scope wont see 200V until the probe is at 2000v p-p. But obviously you have to take into account spikes on the signal you're measuring, as they will be above your signal voltage. So actually putting 2000V p-p on that x10 probe would be stupid, any spikes would overvolt your scopes 200v max input. So maybe you decide to only use it for measuring 1000V p-p so you have 1000V extra for spikes without damaging your scope.Or you might choose to use a 100x probe just because your signal is very sensitive to external loading. So you use a 100x probe even through the voltage of your circuit is low enough for even a 1x probe. In this case you may not be dealing with high voltages at all, so you don't want a probe with a huge amount of insulation that is big and cumbersome to use.The second thing is the probes size/shape. How safe is it to use it on your circuit.If you're working on tiny 0.5mA high voltage supply then maybe a typical looking small 10x probe would be fine for that at 1000V. On the other hand, if you are measuring 1000V that can supply 100A then using that same probe would be crazy. You will see 10x or 100x probes that are huge with large red plastic insulation and others that look like normal probes. It's not just the voltage the probe and scope can handle, it's the dangers from what you are measuring.Just because a probe says 10x, 100x or 1000x you can't assume it's ok to use that probe to measure high voltage.It maybe ok for the scope (voltage wise), but may not ok for you (safety wise)

author: bdunham7
author_rank: Super Contributor
timestamp: April 04, 2024, 01:33:01 am
content: Quote from: 2X on April 03, 2024, 09:12:58 pmIt's a good question. Both are 50M 7.5pF input and the only difference seems to be the final divider value. They have peak or pulse ratings of 6kV so perhaps if you don't want to deal with the resulting 60V peak with the 100X probe (most scopes can't display that), you'll use the 1000X version instead.

author: Circlotron
author_rank: Super Contributor
timestamp: April 04, 2024, 02:27:31 am
content: The voltage rise time of the circuit under test is something to watch out for too. I've blown x10 probes that are rated at 400V with a voltage that jumps to 400V in 1uS. Fast rise times can be a probe killer.

author: 2X
author_rank: Frequent Contributor
timestamp: April 04, 2024, 08:07:11 am
content: Can you see what is the purpose of existing 2 probes x100 & x1000 with same characteristics? There is a positive advantage of x100 in contrast to x1000?

author: Phil1977
author_rank: Frequent Contributor
timestamp: April 04, 2024, 10:35:48 am
content: Please don't get me wrong, but as long as you need help to understand the probe characteristics I wouldn't recommend connecting the scope to mains or to any inverter...What you probably need to do it safe is a high voltage differential probe. With that utility, you do much harder to destroy anything just by its connection. And though it costs around €200,- it seems cheaper than a decent scope or the hospital bill.Trying to be constructive: Do you know "high voltage differential probes"? Do you want more information about them?The thing with mains voltage and non differential probes just is that grounding the probe easily causes catastrophy. Even with an isolation transformer, sometimes even with a galvanically isolated scope. With the HV differential probe you really do not need to worry about ground, and even better their inputs are symmetrical. It´s the only way to measure common mode signals, and mains and inverters are always good for (unexpected) common mode distortions.

author: bdunham7
author_rank: Super Contributor
timestamp: April 04, 2024, 01:58:39 pm
content: Quote from: 2X on April 04, 2024, 08:07:11 amThe 100X probe shows small signals 10X higher at the scope. So if you needed the probe to work for 2kV and for 2V, at 2V the 100X probe gives you 20mV at the scope vs 2mV (which may not look as clear) for the 1000X.

author: 2X
author_rank: Frequent Contributor
timestamp: April 04, 2024, 07:26:26 pm
content: Do you suggest this probes for measuring the output voltage of backlight inverter for driving CCFL lamps where is ~1000Vrms? Both probes they have Maximum Input Voltage 1000Vrms, so I beileive it is on the probe limits. If you agree on that and you know any other good quality brand with probes x100 & x1000 please suggest me.

author: 2X
author_rank: Frequent Contributor
timestamp: April 04, 2024, 07:28:56 pm
content: Quote from: bdunham7 on April 04, 2024, 01:58:39 pmFor similar reason because my oscilloscope when I bought it had only two probes x10 and I want to see a small signal without noise from the x10 attenuation I bougth x1 probe.

author: DaneLaw
author_rank: Frequent Contributor
timestamp: April 04, 2024, 09:40:27 pm
content: Quote from: 2X on April 04, 2024, 07:28:56 pmWhat oscilloscope do you have?

author: 2X
author_rank: Frequent Contributor
timestamp: April 04, 2024, 09:48:55 pm
content: Quote from: DaneLaw on April 04, 2024, 09:40:27 pmhttps://www.rohde-schwarz.com/ae/products/test-and-measurement/oscilloscopes/rs-rtc1000-oscilloscope_63493-515585.html

author: 2X
author_rank: Frequent Contributor
timestamp: April 05, 2024, 10:37:02 pm
content: I found the below probe where have 2000V@3MHz & 1000V@7MHz (DC + AC Peak) max input voltage. Have anyone used it on 1000Vrms? I beleive his specs are good enough for these that I want to measure. Whatever product I have used from BK it was good quality.BK Precision PR2000B 200 MHz 2 kV Oscilloscope High Voltage Probehttps://www.instrumentation2000.com/b-k-precision-pr2000b.htmlhttps://www.instrumentation2000.com//media/pdf/bk-pr2000b-manual.pdfAlso, I found and the below but I beileve is too much.https://www.instrumentation2000.com/cal-test-ct4432-oscilloscope-probe.html

author: bdunham7
author_rank: Super Contributor
timestamp: April 05, 2024, 10:46:46 pm
content: Quote from: 2X on April 05, 2024, 10:37:02 pmThat should work, but since you're in the EU, the very similar looking Testec TT-HV 250 might be easier to come by.https://www.testec.de/en/products/product-categories/standard-probes/How much current loading can your CCFL driver take? These probes have good input impedances--100M and 4 or 5pF--but you need to make sure that even the small 5pF won't cause too much loading. You'd need to know approximately the frequency and current capability of your CCFL system to calculate whether loading will be an issue.

author: 2X
author_rank: Frequent Contributor
timestamp: April 05, 2024, 10:57:58 pm
content: Quote from: bdunham7 on April 05, 2024, 10:46:46 pmI found the BK precision probes on mouser electronics so it is not a problem the shipping. I have never used Testec probe or any other product of this brand... It has better, same or lower quality and safety from BK precision?From searching on the internet and from the below waveform I found that the frequency is approximatelly ~50KHz and the current ~10mA, so I beleive the loading from the probes will be imperceptible.https://www.researchgate.net/figure/Measured-CCFL-voltage-05-KV-div-and-current-33-mA-div-when-driven-by-a-PT-based-HF_fig2_3281120

author: bdunham7
author_rank: Super Contributor
timestamp: April 05, 2024, 11:05:58 pm
content: The BK/Cal Test probes are made in Taiwan, the Testec say they're made in Germany and I haven't heard anything bad about either. Others have recommended the Testec TT-HV 250 but I haven't tried it.At 50kHz and 1000VRMS, you'll have an input impedance that is dominated by the capacitor at about 636k and a resulting current of about 1.5mA (90 degrees leading). Note that this does not mean the probe is dissipating 1.5 watts! This may have some effect on the circuit but it isn't too bad and it may not mind at all since it gets most of the energy back--the 1.5mA is mostly recirculating. Circuit loading can make it very difficult to accurately scope HF/HV signals!

author: KungFuJosh
author_rank: Super Contributor
timestamp: April 05, 2024, 11:09:58 pm
content: I have the BK probe, and it's good, but I've never gone over ~500V with it.

author: 2X
author_rank: Frequent Contributor
timestamp: April 05, 2024, 11:19:31 pm
content: Quote from: bdunham7 on April 05, 2024, 11:05:58 pmThanks for the reply. One thing I didn't catch... Why the probe will not dissipating 1.5 watts ... it gets most of the energy back--the 1.5mA is mostly recirculating?

author: 2X
author_rank: Frequent Contributor
timestamp: April 05, 2024, 11:20:39 pm
content: Testec TT-HVP-40https://www.batronix.com/shop/measurement/probes/Testec-TT-HVP-40.htmlTestec TT-HVP-2739https://www.batronix.com/shop/measurement/probes/Testec-TT-HVP-2739.html

author: bdunham7
author_rank: Super Contributor
timestamp: April 06, 2024, 12:00:04 am
content: Quote from: 2X on April 05, 2024, 11:20:39 pmThe first is useless for you (it is only a low BW tool) and the second is massive (literally) overkill. I would use my Tek P6015s for this, but I happen to have them--I wouldn't buy them for this occasion.As far as recirculating or reactive currents, that's just basic AC circuit theory that you should get acquainted with. When you put a capacitor across a sinusoid AC source, there is in fact a current and it is also a sinusoid, but it is out of phase by 90 degrees (leading the voltage) and therefore half of the time energy is being transferred to the capacitor and half them time it is being transferred from the capacitor, less any losses of course. If losses are low, there is very little energy actually lost in the process. If your signal is not sinusoidal, things get more complicated but the same basic principles apply.

author: 2X
author_rank: Frequent Contributor
timestamp: April 06, 2024, 07:46:17 am
content: Quote from: bdunham7 on April 06, 2024, 12:00:04 amI didn't combine the 90 degrees out of phase with you wrote. Thanks for your reply. Also, I found and the below that you told me.https://www.batronix.com/shop/measurement/probes/Testec-TT-HV-250.html

author: Phil1977
author_rank: Frequent Contributor
timestamp: April 06, 2024, 07:47:28 am
content: That´s exactly the reason why I think you can get good results only with a differential probe.With high voltage and high frequency, you have capacitors literally everywhere. If you use your probe without grounding, you have no idea about what your reference plane is doing - except you use two identical probes and do the differential math in the scope.If you use probe grounding, you ether blow up your circuit or *massively* change the circuit by inducing a new low-z-connection where there is none in the original circuit. Galvanic isolation works only for DC or very low frequency AC, never for HF.Please appologize if the first answer to your question was not very nice, but - without knowing special details - you just can not meassure with non-differential probes. And please don't think I didn't try to...

author: Phil1977
author_rank: Frequent Contributor
timestamp: April 06, 2024, 08:20:39 am
content: PS: A possible answer why x1000-probes exist: If you work a lot on HV-stuff you may also have unintentional discharges. A x100-probe transfers by design 10 times as much of the transient to the scope than a x1000-probe, so if the datasheet values are exceeded anyhow, then it´s of advantage to protect the scope instead of the probe.Maybe there are also some instruments that just don't have a -/-50 V input range.But as long as you use everything in spec, I can't see a good reason why the probe attenuation factor should make a great difference.

author: 2X
author_rank: Frequent Contributor
timestamp: April 06, 2024, 08:25:21 am
content: Quote from: Phil1977 on April 06, 2024, 07:47:28 amThanks for you replies. I have made quite experiments with oscilloscope but fortunately I hadn't blow up something yet and because I know all the danger with the grounding I ask to many things here. In same cases the the groung was not so clear how is arranged on the PCB I have used two identical probes and I 've done the differential math in the oscilloscope but I had noise on the measured signal because the ground clips are not connectioned. I have used differential probe but I would like to risk and measure with "ordinary" probes. Always there is something to new even with risk.I am close to select the two below for buying. They have good specs for what I want to experiment/measure.Testec TT-HV-250https://www.batronix.com/shop/measurement/probes/Testec-TT-HV-250.htmlTestec TT-HVP-2739https://www.batronix.com/shop/measurement/probes/Testec-TT-HVP-2739.html

author: tooki
author_rank: Super Contributor
timestamp: April 06, 2024, 09:50:40 am
content: Quote from: 2X on April 05, 2024, 10:57:58 pmI have used many Testec probes and quite like them. Great quality at reasonable prices. The grips are a bit fatter than many probes, which I happen to like. I have some Testec at work and some at home.Hameg (the test equipment company R&S purchased in order to break into the general test and measurement industry) shipped rebadged Testec with their scopes. (R&S now ships probes from another German manufacturer, PMK, which is more focused on high-bandwidth probes.)

author: Phil1977
author_rank: Frequent Contributor
timestamp: April 06, 2024, 10:04:21 am
content: Quote from: 2X on April 06, 2024, 08:25:21 amOkay, to learn abouts whats happening it absolutely makes sense to do the math in the scope. But if you (also) want to learn from other peoples experience, usually the quality of the results with a "analouge computer" in the probe circuitry is much better than whatever the scope can do digitally.Personally I´d rather *only* use the differential probe, and if I want to measure against instrument ground I can also connect the "-"pole of the differential probe to instrument ground. It´s just THE big advantage of any differential probe, you can always select by yourself what part of the circuitry should be ground now. With the conventional probe you just don't have this choice.Of course there are always many valid ways to many valid targets

author: 2X
author_rank: Frequent Contributor
timestamp: April 06, 2024, 07:51:26 pm
content: Quote from: tooki on April 06, 2024, 09:50:40 amHameg oscilloscopes are very robust oscilloscopes... lifetime equpment.