Keyboard Shortcuts
ctrl + shift + ? :
Show all keyboard shortcuts
ctrl + g :
Navigate to a group
ctrl + shift + f :
Find
ctrl + / :
Quick actions
esc to dismiss
Likes
Search
Cheap differential probe ?
|
Bob Albert
Try ebay.
toggle quoted message
Show quoted text
Bob On Thursday, March 1, 2018, 6:11:02 PM PST, David Slipper <softfoot@...> wrote:
Can anyone suggest a source of the above ?? DC to 20MHz would be more than adequate. I don't even need a high voltage device - 30V would be OK, 100V would be better. I'd even consider a DIY or kit implementation. Any suggestions? TIA Dave |
|
There is no such thing as a cheap differential probe. They have to be matched across a wide frequency range to have good CMRR. If you want a cheap CMRR the solution may be on your scope. All dual trace scopes have an ADD function for both traces. They all haave a way to invert a trace on one of the channels. So switch to Add, Invert one channel, and use the gain knob of one channel to adjust the trace to a straight line when you put a signal in through two same number probes - any two will do as long as they are the same (two P6109 probes for example).
toggle quoted message
Show quoted text
Voila, a poor man's Differential probe. As long as there isn't too much of a voltage difference between the two channels the waveform will stay on the screen where this will work OK. It isn't much but that is probably the best you are going to get when you require "cheap" Dennis Tillman W7PF -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of David Slipper Sent: Thursday, March 01, 2018 6:45 PM To: [email protected] Subject: Re: [TekScopes] Cheap differential probe ? Sadly, nothing under ?100 on fleaBay :-( Anything in the DIY arena ?? Dave -- Dennis Tillman W7PF TekScopes Moderator |
|
Dave-
toggle quoted message
Show quoted text
You might consider going to ham radio swap meets. A really great FET differential probe is the Tek P6046. I picked up one for less than $50 if I remember correctly and it is perfect. Many people do not know what they are and that accounts for them selling so cheaply. It takes some time to find one but at least you'll be rewarded with a great tool once you do. Phil On 3/1/2018 6:10 PM, David Slipper wrote:
Can anyone suggest a source of the above ?? |
|
Dennis' suggestion of using add and invert mode on the oscilloscope
toggle quoted message
Show quoted text
works well depending on how much sensitivity you need. If you have a 7000 mainframe, then a 7A13 combined with standard x1 probes may be acceptable. Standard x10 probes have the problem of not having matched attenuation which spoils the common mode rejection. Another alternative I have occasionally used is to build the probe into the circuit using a fast instrumentation or difference amplifier. On Fri, 2 Mar 2018 02:10:49 +0000, you wrote:
|
|
Dave, if you want to roll your own get a copy of 'Electronics and Wireless World"
DEC 2001 from yr local library. Page 922 has article 'Differential-in 100Mhz scope probe" by Cyril Bateman. PC boards would not be available from him now, but his fully specified circuit and construction methods should help you achieve your aim. and be easily down gradable to your target of 20MHz bandwidth with lower spec'd IC's Some Specs are : CMR : < 10Mhz >80dB>,70dB at 10MHz, 49dB at 120MHz (Ref 1V input and 10:1 attenuation set) MAX4005 used inside the probes,MAX 4144 and MAX4107 used inside the direct input to scope box. Copper pipe used for probe bodies. Its also easy to calibrate and adjust. Cyril is (was?) a professional design engineer and a consultant on capacitor design. He produced quite a few bits of pro spec'd test instrumentation in E&WW and his Cap esr tester is likely to have been (and still be ) the most accurate esr meter so far ever designed for both enthusiast and semi pro work I considered getting his PC boards at the time, but got myself a TEK P6046 and amplifier unit which both worked and were in spec (If you are thinking of buying these be aware that not many are now in fully specified or even in working condition) John |
|
Thank You!!
toggle quoted message
Show quoted text
After persevering with Google Search I have found a few designs of varying complexity that could suit me, good old WW - now the fun begins. Regards, Dave On 03/03/2018 02:59, hpxref wrote:
Dave, if you want to roll your own get a copy of 'Electronics and |
|
Hello,
May or may not be a fit for your application or budget, but I saw this on page 69 of the March 2018 RSGB magazine: Micsig DP10013 100 MHz high voltage differential probe, about GBP150 Also found on amazon.com for about $170 I do not have one, and have no affiliation with that company (I just subscribe to RSGB). Hope that it helps. Scott |
|
Jim Williams tackled this
On Thu, Mar 1, 2018 at 9:54 PM, Dennis Tillman W7PF <dennis@...> wrote: There is no such thing as a cheap differential probe. They have to be |
David Hess
to navigate to use esc to dismiss