Loading... |
Reply to author |
Edit post |
Move post |
Delete this post |
Delete this post and replies |
Change post date |
Print post |
Permalink |
Raw mail |
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
568 posts
|
Gary Hvizdak wrote:
> You can read the full text of Alan's post in the Reflector archives at > http://mailman.qth.net/pipermail/elecraft/2008-February/083794.html Fred wrote: >Ingenious test set up Alan used to measure 1.0E10 ohms. I must be missing something in the test description. Wouldn't the very low internal resistance of the Simpson voltmeter grossly swamp the effects of the very high resistance of the mat? Even the input resistance of a VTVM would be very low compared to the resistance that is to be measured (even if measurement is only periodically made on the circuit). Mike / KK5F ______________________________________________________________ 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 |
Loading... |
Reply to author |
Edit post |
Move post |
Delete this post |
Delete this post and replies |
Change post date |
Print post |
Permalink |
Raw mail |
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
845 posts
|
> I must be missing something in the test description. Wouldn't the
> very low internal resistance of the Simpson voltmeter grossly swamp > the effects of the very high resistance of the mat? Yes. What is happening is that the capacitor is discharging through the meter in a millisecond or so. The meter needle jumps up only a small amount because of the damping in the meter movement. The only reason that technique works is that the absolute meter reading is not important, only the ratio of two readings. The meter jumped to about 1/10 scale when the capacitor was charged to 15V. So a few minutes later when the meter jumped to 1/20V, I deduced that the capacitor voltage must have been 7.5V. Alan N1AL On Sun, 2010-03-28 at 13:45 -0500, Mike Morrow wrote: > Gary Hvizdak wrote: > > > You can read the full text of Alan's post in the Reflector archives at > > http://mailman.qth.net/pipermail/elecraft/2008-February/083794.html > > Fred wrote: > > >Ingenious test set up Alan used to measure 1.0E10 ohms. > > I must be missing something in the test description. Wouldn't the > very low internal resistance of the Simpson voltmeter grossly swamp > the effects of the very high resistance of the mat? Even the input > resistance of a VTVM would be very low compared to the resistance > that is to be measured (even if measurement is only periodically > made on the circuit). > > Mike / KK5F > > > > ______________________________________________________________ > 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 ... [show rest of quote] ______________________________________________________________ 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 |
Free forum by Nabble | Edit this page |