Probing question - Page 1
Forum section: electronics / beginners

author: tony3d
author_rank: Frequent Contributor
timestamp: November 24, 2013, 06:38:49 pm
content: Ok, i'm about to buy my first scope. Haven't used one since high school.Could I'm bit concerned about blowing up my first scope do to inexperience with scopes. I have read things about the probe ground wire can cause damage if connected to the wrong part of a circuit or something. I would never try reading ac off the wall. So how can I accidentally damage my scope by probing?

author: DL8RI
author_rank: Regular Contributor
timestamp: November 24, 2013, 06:52:19 pm
content: Hi,for example:You probe a Amplifier. For this you insert a signal with a function Generator via RCA.Then you want to look at the ripple of the Power-Supply while the Amplifier is working.... well, ground wire to the pos rail and BAM.If you ground your circuit somehow, you have to be careful what to do with the Scope-GND-Wire.

author: tony3d
author_rank: Frequent Contributor
timestamp: November 24, 2013, 08:44:04 pm
content: Quote from: DL8RI on November 24, 2013, 06:52:19 pmSo long as you always connect the ground of the probe to the negative side if the circuit you should be fine correct?

author: Unknown
author_rank: Unknown
timestamp: November 24, 2013, 08:51:52 pm
content: Wasn't there some crazy bloke from Austria or something that made a video about how not to blow up your scope?

author: JOERGG
author_rank: Contributor
timestamp: November 24, 2013, 08:54:59 pm
content: Quote from: alm on November 24, 2013, 08:51:52 pmAustralia, not Austriahttp://www.eevblog.com/2012/05/18/eevblog-279-how-not-to-blow-up-your-oscilloscope/

author: tony3d
author_rank: Frequent Contributor
timestamp: November 24, 2013, 09:10:52 pm
content: Thanks I missed that one. I am still undecided as to which one of these scopes to order.Owon SDS5032ESiglent SDS1072CMLSiglent’s SDS1102CMLHANTEK DSO5102BI guess I'm leaning towards the Rigol, but the Siglent, and Hantek both look good as well. If the Owon wasn't so slow, that would probably be my choice. Any input would be great! Plan to order in the next few days.

author: Avotronics
author_rank: Regular Contributor
timestamp: November 24, 2013, 10:03:46 pm
content: If you haven't already watched the video above from Dave, watch it.It's a good idea to have an isolation transformer for the device under test, especially when working with high voltages, but don't be fooled into thinking that one will make everything okay. You really need to be awake when working with scopes because its very easy to attach your ground clip to the wrong part and boom. If you are working with power supplies, specifically the primary side, then you need to look at the alternative methods for keeping yourself and the scope safe. Placing your ground clip on the primary side (hot) ground will fry your scope and maybe also you. The two options commonly used are differential probes and floating the scope, but many folks here with advise you not to float it for safety reasons. Differential probes are wickedly expensive however.Two more options. Find a scope with isolated inputs (channels) these are usually expensive bench scopes or handheld scopes, or, find a bench scope with a battery like some of the Owon ones. Note: Owen specifically advise use of the earthed mains plug even when on battery, because you are effectively floating the scope otherwise.Much reading you must do young skywalker.Out of interest, me and my colleague have always floated scopes (I am not endorsing it mind) but once in our new workshop he forgot to remove the scopes earth but told me he had. Next time I probed the smps primary side there was a bang, the rcd tripped and I thought, shucks, that's the scope fried. Luckily, it was fine and I just needed to reset the rcd. Scopes been calibrated since with no problem, but it is a great tektronixs scope of ten years, doubt the Rigol or any modern DSO would stand the same.

author: sdg
author_rank: Regular Contributor
timestamp: November 24, 2013, 10:55:46 pm
content: Quote from: tony3d on November 24, 2013, 09:10:52 pmGet yourself a cheap old scope, learn how to fry (and repair) it and buy one of these once you've grown out of being a padawan...

author: DL8RI
author_rank: Regular Contributor
timestamp: November 24, 2013, 11:08:20 pm
content: Quote from: tony3d on November 24, 2013, 08:44:04 pmNo, it's all about where you "earth"-ground-reference your circuit.If you want to, you can ground-reference the 16kV acceleration Voltage of a Tube. You should not touch anything after that, but in theory you can do it(if your measurement-EQ can isolate it)If you have one floating circuit, you can do whatever you want (nearly), but if you have another connection besides the scope, you have to watch what you're doing.

author: Filter_head
author_rank: Contributor
timestamp: November 25, 2013, 12:29:36 am
content: A good reason to spend a few bucks on an isolation transformer for the DUT!

author: Six_Shooter
author_rank: Regular Contributor
timestamp: November 25, 2013, 12:30:35 am
content: Quote from: JOERGG on November 24, 2013, 08:54:59 pmI was just about to post that same link.Dave has some other equipment tutorials on his Youtube channel as well.