Choosing oscilloscope probes - diyAudio
Go Back   Home > Forums > Design & Build > Parts
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Parts Where to get, and how to make the best bits. PCB's, caps, transformers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 7th May 2007, 07:28 PM   #1
diyAudio Member
Join Date: Dec 2003
Location: Montreal
Default Choosing oscilloscope probes

I bought two "oscilloscope+FFT analyzer+logic analyzer" ISA cards recently on eBay without probes. These are my first "'scopes" and I'd like to know what kind of probes I should buy. With these cards, I can either choose to have one single 200MHz channel or two 100MHz channels per card.

But, since they are not linked together, if I put both in 200MHz mode, they act as two separate 'scopes, so comparing between both signals is not possible.

I know absolutely nothing to probes, what should I get?
  Reply With Quote
Old 8th May 2007, 11:44 AM   #2
diyAudio Member
Join Date: Mar 2007
You shold be able to use virtually any scope probe, but best to get them both for 200 Mhz since your cards will go up to 200 Mhz sample rate. This is assuming that the cards or some part of your system have two BNC connectors, one for each probe, one on to each channel input.

There are always loads of Scope probes available on Ebay at about 5- 10 each.

Hope this helps
  Reply With Quote
Old 8th May 2007, 11:44 AM   #3
diyAudio Member
Join Date: Mar 2007
Further to my last regarding Scope probes with BNC connectors, I have realized that there are available scope probes for sound card scopes and these have Phono plug connectors so these should be available also.

There should be no reason why you should not be able to cut off the BNC connectors and fit Phono's instead but the BNC is better at high frequency than Phono. There may be a difficulty with getting suitable plugs to fit the thin wire that is used, definately better to get the correct type in the first place. It all depends on your card input requirements.

There is another post regarding PC sound card scope probes just down the page, click on the link to see Phono connector scope probes.
  Reply With Quote
Old 8th May 2007, 03:07 PM   #4
diyAudio Member
Join Date: Dec 2003
Location: Montreal
Well, it's not a sound card, it's some real dedicated scopes with BNC connectors.

The thing is, I know I can buy almost any probes out there, but there is also is the fact that there are X1, X10, X100 ones, different coax cables, different connectors, and a big price difference between the probes.

I'd like to narrow the amount of choice to more specific things / what's the most useful, etc.
  Reply With Quote
Old 8th May 2007, 03:13 PM   #5
diyAudio Member
I_Forgot's Avatar
Join Date: Jan 2005
Location: Phoenix, Az.
Probes with phono connectors are definitely not suitable for a 200 MHz sampling scope.

Tektronix has at least one good app note on their web site about choosing scope probes. I suggest you start there.

Decent scope probes have a trimmer capacitor in the little box with the BNC connector. The trimmer is adjusted to match the probe capacitance to the scope's input capacitance using the reference 1 KHz clock on the scope. You typically adjust the capacitance to make the square wave look square. Don't even think about a high frequency measurement without trimming the probe.

  Reply With Quote
Old 8th May 2007, 03:45 PM   #6
diyAudio Member
Join Date: Dec 2003
Location: Montreal
Well, I can't seem to find any interesting info on Tek's site, but I found these:

Much cheaper than Tektronix's $100+ 200MHz probes!
  Reply With Quote
Old 8th May 2007, 03:51 PM   #7
diyAudio Member
jackinnj's Avatar
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
you can make a phono plug which has decent impedance to 150 MHz or so -- it takes a little bit of 5/32" brass tubing and RG-188 coax --

if you aren't going to roll your own connector with an RCA plug and brass tubing -- this is the effect of one RCA phono connector from 100kHz to 200 MHz -- the trace was normalized at 50 ohms -- the vertical scale is 0.05dB/interval.

"A bad probe is worse than a bad wife..."
Attached Images
File Type: png rca.png (29.5 KB, 282 views)
  Reply With Quote
Old 8th May 2007, 04:03 PM   #8
Hartono is offline Hartono  Indonesia
diyAudio Member
Join Date: Nov 2002
Location: currently in China
1.get a cheap x10 probe first, you will always need spare probe later on
x10 is good compromise for start, I'll always have at least 2 of those

typical worst case you will get at least 25 mhz bandwith with cheap 10x probe. make sure it has adjustment.

since higher quality probe is prohibitively expensive, In practice I use the cheap much more to prevent damage from overvoltage, or mishandling.

2.Next step will be high impedance active probe,. you will get at least 100Mhz bandwith for decent price + high impedance input, or you can even make it yourself if you can find a schematic/guide.

3.Differential probe is nice, but expensive.

4.DC+AC current probe is nice to have but extremely expensive.

get number 1 first and study to use it maximally, higher speed probe is useless if not properly used, learn how to use grounding near the tip to get best measurement result at high speed circuit ( 20Mhz ++).
  Reply With Quote
Old 8th May 2007, 07:11 PM   #9
diyAudio Member
Join Date: Dec 2003
Location: Montreal
Again, the cards use BNC, not RCA.

I'll look into what you say Hartono.
  Reply With Quote
Old 8th May 2007, 08:48 PM   #10
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
EC8010's Avatar
Join Date: Jan 2003
Location: Near London. UK
Decent 100MHz probes are cheap. As has been pointed out, it's essential to calibrate them. Avoid switched x1, x10 probes like the plague. Most x10 probes have a voltage limit of only 300V, sometimes less. Worse, there are some x100 probes with the same voltage limit. Only buy a x100 probe if it is good for 2.5kV or more.
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Advice on probes for a oscilloscope.... darkmoebius Chip Amps 6 20th July 2012 05:51 AM
Probes for Tektronix oscilloscope T935A ? 00940 Equipment & Tools 1 14th May 2009 06:09 PM
First scope/buying oscilloscope probes rockgardenlove Equipment & Tools 9 7th November 2008 02:59 PM
Oscilloscope Probes for Tube Work tgorham3 Tubes / Valves 2 18th March 2008 09:20 PM
Oscilloscope probes for sound card stef1777 Parts 4 9th May 2007 09:55 PM

New To Site? Need Help?

All times are GMT. The time now is 02:54 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2