what type of probe for such scope - Page 1
Forum section: electronics / testgear

author: paul18fr
author_rank: Contributor
timestamp: October 04, 2014, 06:19:37 pm
content: dear allI've an opportunity to buy a 2nd hand 20 MHz scope (see picture), low price and probably enough in a first step for the beginner and the hobbyist I am ; this scope is provided without the probes and from the picture, there're 2 BNC connectors per channel if I'm right ...So what kind of probe I'll need ? All the probes I find have a single connector ... probably a basic mounting can be used ...Thanks for you point(s) of viewPaul

author: JDubU
author_rank: Frequent Contributor
timestamp: October 04, 2014, 06:36:01 pm
content: This scope has differential inputs.The display will show the difference between the + and - inputs for each channel. Each of these inputs is expecting a separate probe.Normally a differential input for a scope will have a switch which can ground each of these inputs separately so that you can use it single ended (non-differential) mode. If yours doesn't, you could use a "BNC shorting cap" to make the ground connection (do a google search).

author: WVL_KsZeN
author_rank: Regular Contributor
timestamp: October 04, 2014, 06:36:13 pm
content: Wow! that's a differential scopeNice find, I don't know about the probes, but I'd definately get it! You could probably use a normal probe, if you short the - of each channel to the GND of your probe.

author: MadTux
author_rank: Frequent Contributor
timestamp: October 04, 2014, 07:09:32 pm
content: Any cheap 20MHz probe will do it. You need 2 if you want to use the differential input.Else you could also connect a variable voltage DC source (e.g. +/- 0-300V) to the second input so you can use it to see small DC coupled voltages on a high voltage line, useful to check for PSU ripple or high side MOSFET drivers. I have a few 7A13 for that, which I really like

author: tautech
author_rank: Super Contributor
timestamp: October 04, 2014, 07:51:58 pm
content: Nice scope, quite unusual with dedicated Differential inputs for floating and isolated measurements.These are the type of probes it is intended to be used with:http://www.probemaster.com/index.php?cPath=21Usually quite expensive.Have a study of the attached Tek pdf.What probe is connected for the sinewave image in the OP?It looks like it can be used as a standard 2 ch scope.Does it come with user & service manuals?As it is a bit unique, I would be a little nervous without them.For general use get 4 of the P6100 probes, they are acknowledged as perfectly good quality.http://www.ebay.com/itm/P6100-DC-100MHz-Oscilloscope-Scope-Clip-Probe-100MHz-For-Tektronix-HP-x1x10-600V-/191201837365?pt=LH_DefaultDomain_2&hash=item2c84848135

author: paul18fr
author_rank: Contributor
timestamp: October 04, 2014, 09:01:18 pm
content: Thanks for the feebacks and the documentation.Regarding differential probes prices ... definitively out of the possibilities of a basic hobbyistI had a look on internet (ebay or other websites) and one can find the probes by pair .... many have China origin (fake ?)ThanksPaul

author: tautech
author_rank: Super Contributor
timestamp: October 04, 2014, 09:13:54 pm
content: Quote from: paul18fr on October 04, 2014, 09:01:18 pmNot fake. The P6000 series are all ex China.Have a look on Aliexpress too, you might find a lot of 4 for a good price.

author: paul18fr
author_rank: Contributor
timestamp: October 04, 2014, 09:15:50 pm
content: Not fake. The P6000 series are all ex China.Have a look on Aliexpress too, you might find a lot of 4 for a good price.I saw it; thanks for the information

author: edavid
author_rank: Super Contributor
timestamp: October 04, 2014, 09:35:29 pm
content: The problem with trying to use 2 regular scope probes (P6000 or whatever) as a differential pair is that they do not have matched gain, or a gain trim, so the CMRR will suffer a great deal. It's not very practical unless the scope has a differential gain adjustment.

author: Lunasix
author_rank: Regular Contributor
timestamp: October 04, 2014, 10:06:44 pm
content: I have had a Tektronix with differential inputs, but with very high sensibility, probably not the case here. For normal use, you need to connect only one probe (+input, unless you want to see your signal inverted) and select corresponding input. But I don't see on photo (too small) such switch. If not available, simply use a BNC connector shorted on the - input. 50€ is a good price, the scope seems to be in good condition. Probe :http://www.ebay.fr/itm/New-1-Pair-Oscilloscope-Scope-Clip-Probe-100MHz-Measurement-Test-Detector-B98B-/400759343081?pt=FR_YO_MaisonJardin_Bricolage_ElectroniqueComposants&hash=item5d4f1e47e9On the photo, the cable is connected only to - input, it works ! So, don't worry for that.And don't forget : even with differential input and 2 classical probes, reference is always ground. For high voltage, use a special différential probe, powered with battery.