This thread was a SPIN-OFF by the mods. I asked the question in the thread listed above. I DID NOT CREATE THIS TREAD AND I WAS SIMPLY ASKING A RHETORICAL QUESTION!!
I was not aware of that since no mention was made and took it to be a legitimate thread.This thread was a SPIN-OFF by the mods. I asked the question in the thread listed above. I DID NOT CREATE THIS TREAD AND I WAS SIMPLY ASKING A RHETORICAL QUESTION!!
Well, at least my math was right.Yes, it would but if you read the title of the thread.
You may get it from here.Where does one get a 100GΩ resistor?
Obsolete ionization chambers are an inexpensive yet high quality source for such components (e.g. CDV-715 and its ilk) -- the high value resistors (typically up to 220GΩ) are encased in glass envelopes to facilitate maintenance of cleanliness...Where does one get a 100GΩ resistor?
I´d still blame this to poor reading skills, posts #4 and #17 were the clues.... Poor writing skills on your part does not imply poor reading skills on our part. ...
I ran into this problem recently while sorting through a large batch of LDRs looking for units that had exceptionally high dark resistance. My bench DMM only goes up to 50 MΩ, and many of the LDRs had dark resistance well above 1 GΩ, with some approaching 100 GΩ.Rethorical it was; here is the logical follow up: how to measure it? A true Georg Simon moment.
Aha, a divider. I should have thought of that...! Wondering how the actual value of the small one would affect the measurement of the big one. I will try something later. On paper, I mean.I ran into this problem recently while sorting through a large batch of LDRs looking for units that had exceptionally high dark resistance. My bench DMM only goes up to 50 MΩ, and many of the LDRs had dark resistance well above 1 GΩ, with some approaching 100 GΩ.
Easiest solution I came up with was to form a voltage divider with the unknown resistance (the LDR) on top and a 1 MΩ resistor on the bottom, then calculate the unknown resistance from the applied voltage and the voltage measured across the 1 MΩ resistor.
I'm sure you can buy instruments that will directly measure and display such large resistances, but I shudder to think what they must cost. The voltage divider method is cheap, easy and accurate, though a bit slow. But being retired, I've got lots of time on my hands...
Don't feel bad. After doing analog circuit design for a living for over 40 years, I can't BELIEVE how much head-scratching I had to do before that simple idea came to me.Aha, a divider. I should have thought of that...!
It just comes down to using the voltage divider formula, taking into account the DMM's input resistance being in parallel with the 1 MΩ resistor. Given that my DMM's input resistance is 100 MΩ, the 1 MΩ resistor had a 1% tolerance, and I wasn't really interested in getting a terribly precise measurement anyway, I did a simplified calculation:Wondering how the actual value of the small one would affect the measurement of the big one.
Rethorical it was; here is the logical follow up: how to measure it? A true Georg Simon moment.
Surprisingly, the price of acceptably accurate (± 2%) instruments is quite reasonable!I'm sure you can buy instruments that will directly measure and display such large resistances, but I shudder to think what they must cost.
Wow, 2TΩ!! All secured to a two mundane (are they?) crocs?? And then the sandapaper... Not a game I could expect to play in this life, it seems.Surprisingly, the price of acceptably accurate (± 2%) instruments is quite reasonable!
For instance, I can personally vouch for the offerings of Alphalab for accurate resistance measurement up to 2TΩ (2000GΩ) -- especially useful where application of EHT is contraindicated...
Best regards
HP
How much Vin was?Runknown ≈ 1 MΩ ⋅ Vin / Vmeter.
Accurate enough for my purposes...
Many megger units will read to 2 G (1999 meg) easily enough and I have seen a few 'Giggers' (1999 G) for HV utility cable and related testing before as well.I ran into this problem recently while sorting through a large batch of LDRs looking for units that had exceptionally high dark resistance. My bench DMM only goes up to 50 MΩ, and many of the LDRs had dark resistance well above 1 GΩ, with some approaching 100 GΩ.
by Jake Hertz
by Aaron Carman
by Duane Benson
by Jake Hertz