Buying good quality oscilloscope probe - Page 1
Forum section: electronics / testgear

author: msimunic
author_rank: Contributor
timestamp: January 25, 2020, 10:07:07 am
content: Hi,I want to buy a 50 MHz - 100 MHz bandwidth oscilloscope probe(s) (1 or 2 pieces) for My 50 MHz scope. It is an analog scope with a plain simple BNC connector and 1 MOhm || 25 pF input impedance.I need a good quality probe suited for 300 V AC line measurements. I prefer probe with 1x/10x switch, but 10X only would also be ok. Probe with 100X attenuation, ~kV rated are also an option. Although, 90% of measurement I will do will be in 50 MHz and 20 Vpp range.With little experience, I'm not sure which brands are good (except Tektronix nad Keysight). I'm considering to buy a new probe or a used one.I'm just not sure is used probe a good choice, because ... well, who knows what happened to it.Any advice would be helpful. Thank you.

author: tautech
author_rank: Super Contributor
timestamp: January 25, 2020, 10:45:28 am
content: Quote from: msimunic on January 25, 2020, 10:07:07 amDo yourself a big favor and get 100:1 probes for mains work.For general LV work cheap P6100 probes are just fine.

author: bd139
author_rank: Super Contributor
timestamp: January 25, 2020, 10:55:18 am
content: Totally agree with tautech. On the cheap probes the P6100s are actually better than a lot of the brand ones these days. But yes 100X

author: nctnico
author_rank: Super Contributor
timestamp: January 25, 2020, 11:09:26 am
content: For measuring mains I'd recommend getting a differential probe. The ones from MicSig are very affordable.General purpose probes are pretty cheap nowadays. I like the ones from Testec. Consider general purpose probes to be consumable; the cable will break at some point.

author: tggzzz
author_rank: Super Contributor
timestamp: January 25, 2020, 11:41:58 am
content: Quote from: msimunic on January 25, 2020, 10:07:07 amThe first thing to do is to define what you want the measurement to show. It may be that an oscilloscope is the wrong rool for your job.There are many dangers, some subtle, associated with measuring mains voltages. Most are avoided by using an HV differential probe. When people without such a probe run into difficulties, they sometimes disconnect the scope's protective mains earth - that islethaland shouldneverbe done.QuoteSooner or later the switch will be in the *1 position when you want/need it in the *10 position. With high voltages that is a real problem!QuotekV probes are another issue. You will need a separate probe for that.QuoteMake sure you understand theprobe'smax voltage as a function of frequency. Get that badly wrong and the probe will meltI strongly suggest you look a the safety references inhttps://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/before spending money and before doing experiments.

author: msimunic
author_rank: Contributor
timestamp: January 25, 2020, 04:18:19 pm
content: More or less I understand issues about mains measurement, but yes, thank you for advice. It's good to remember a few things.There are four brands of probes that seem ok, but which I know nothing about: TENMA, POMONA, TESTEC and Cal Test Electronics.Anyone has experience with those probes? - I mean, quality of build, quality of material and ergonomy.

author: tggzzz
author_rank: Super Contributor
timestamp: January 25, 2020, 04:28:39 pm
content: Quote from: msimunic on January 25, 2020, 04:18:19 pmYour first post mentions 300Vac and preferring *1/*10 probes.Beverycareful that you reallydounderstand how to probe mainssafely.

author: joeqsmith
author_rank: Super Contributor
timestamp: January 25, 2020, 04:39:17 pm
content: Quote from: tggzzz on January 25, 2020, 11:41:58 amYou could tape the switch it it's a concern.QuoteI looked at a cheap 100X probe and damaged it well below their published derating curve. If you really need a 100X probe, I suggest getting something from a reputable source.