I like the way scope probes have a tip that hooks onto a component lead,
and a little alligator clip for the ground. So I thought I could use a passive scope probe in the X1 position on my DVM too. I hooked one up with a BNC-bannana adapter, but it turns out that there seems to be a series resistance of about 250 ohms, which is inconvenient for resistance measurements. I got the same result from several probes. My question is, what's going on here? Schematics of probes I found all showed that in the X1 position they were straight through. -- 73, Victor, 4X6GP Rehovot, Israel Formerly K2VCO CWops no. 5 http://www.qsl.net/k2vco/ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
On 5/4/2020 7:47 AM, Victor Rosenthal 4X6GP wrote: > ... My question is, what's going on here? Schematics of probes I found > all showed that in the X1 position they were straight through. Check the resistance of the adapter without the probe. Gus Hansen KB0YH ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
In reply to this post by Vic Rosenthal
Look at this article: "THE SECRET WORLD OF OSCILLOSCOPE PROBES" by Doug Ford.
It will explain where the extra resistance is coming from and what it is for (TLDNR - it's for suppressing ringing of 1:10 probe at high frequencies where the cable of the probe starts looking like a transmission line). http://www.dfad.com.au/links/THE%20SECRET%20WORLD%20OF%20PROBES%20OCt09.pdf On Mon, May 4, 2020 at 6:48 AM Victor Rosenthal 4X6GP <[hidden email]> wrote: > > I like the way scope probes have a tip that hooks onto a component lead, > and a little alligator clip for the ground. So I thought I could use a > passive scope probe in the X1 position on my DVM too. I hooked one up > with a BNC-bannana adapter, but it turns out that there seems to be a > series resistance of about 250 ohms, which is inconvenient for > resistance measurements. I got the same result from several probes. > > My question is, what's going on here? Schematics of probes I found all > showed that in the X1 position they were straight through. > -- > 73, > Victor, 4X6GP > Rehovot, Israel > Formerly K2VCO > CWops no. 5 > http://www.qsl.net/k2vco/ > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] -- Alexey Kats (neko) ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Thank you, that explains it (and more)!
73, Victor, 4X6GP Rehovot, Israel Formerly K2VCO CWops no. 5 http://www.qsl.net/k2vco/ . On 04/05/2020 20:28, demindor . wrote: > Look at this article: "THE SECRET WORLD OF OSCILLOSCOPE PROBES" by Doug Ford. > > It will explain where the extra resistance is coming from and what it > is for (TLDNR - it's for suppressing ringing of 1:10 probe at high > frequencies where the cable of the probe starts looking like a > transmission line). > > http://www.dfad.com.au/links/THE%20SECRET%20WORLD%20OF%20PROBES%20OCt09.pdf > > On Mon, May 4, 2020 at 6:48 AM Victor Rosenthal 4X6GP > <[hidden email]> wrote: >> >> I like the way scope probes have a tip that hooks onto a component lead, >> and a little alligator clip for the ground. So I thought I could use a >> passive scope probe in the X1 position on my DVM too. I hooked one up >> with a BNC-bannana adapter, but it turns out that there seems to be a >> series resistance of about 250 ohms, which is inconvenient for >> resistance measurements. I got the same result from several probes. >> >> My question is, what's going on here? Schematics of probes I found all >> showed that in the X1 position they were straight through. >> -- >> 73, >> Victor, 4X6GP >> Rehovot, Israel >> Formerly K2VCO >> CWops no. 5 >> http://www.qsl.net/k2vco/ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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