100 meg resistor thick film- limited time

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Richard Hull
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100 meg resistor thick film- limited time

Post by Richard Hull »

Electronic gold mine is selling as of 8/4/22 this rare item for those scaling voltmeters or doing special electrometer work.

https://www.goldmine-elec-products.com/ ... 3-60335069

Typically they have x number of these and when gone, they are gone.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.
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Aidan_Roy
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Re: 100 meg resistor thick film- limited time

Post by Aidan_Roy »

Not sure if this is the appropriate spot, however I found these a month or so ago and seller negotiates for bulk buying. They look very similar to your find Richard.

100MOhm, 20kV, 2.5 watts, 1 percent axial ohmite resistors

https://www.ebay.com/itm/263777066599?m ... media=COPY
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Richard Hull
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Re: 100 meg resistor thick film- limited time

Post by Richard Hull »

These look great too. Nice find. Tough to find at decent prices. 100meg is an ideal HV voltmeter chaining value.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.
Rex Allers
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Re: 100 meg resistor thick film- limited time

Post by Rex Allers »

I saw those "Goldmine" resistors. They don't provide a voltage rating but they are about 1" long. I checked my stash and found some similar 100M resistors. They are rated at 6.5 kV.

The ebay listing looks better as they are 20 kV parts.

For something like measuring output voltage on a geiger counter, 1 G ohm on the probe divider is usually recommended to not pull down the weak supplies. So it would take 10 of these in series for 1 G ohm.

For a divider to measure fusor voltages, say, 30 to 50 kV, I would prefer using 200 M with the style of the ebay listing ones. I haven't seen any good deals on 200 M and my stash currently has none.

As an example, I have looked at several Glassman HV supplys. (They used to share schematics in their manuals.) Their voltage sensing dividers usually use 200 M 20kV resistors with style of the blue ones in the ebay listing. They implement a max voltage of 10 kV across each stage. So if the supply had a max 50 kV out the divider would have five 200 M resistors in series.

So to use the 100 M in the same way a 50 kV divider would need 10 resistors. If the shorter 100 M were rated 6.5 kV, the chain of ten would be 65 kV so ok. Based on the voltage rating of the ebay 100 M, you could use just 3 to measure 50 kV but that would draw a bit over 8 W which is more than their rated 2.5 W x 3.

When trying to find good deals, you take what you can get, but do the math on application for these. Anything workable is better than nothing.
Rex Allers
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Richard Hull
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Re: 100 meg resistor thick film- limited time

Post by Richard Hull »

Bumble Bee resistors are old school but usually will handle much higher voltages as they are longer, per unit resistance. There tolerance is never better than 5% and a bit of trimming with 10 meg resistors is often needed and calibrated against a known source. I tend to cal. against my glassman 0-30kv 3ma supply with its built in digital meter.

Still, when we are at 45kv what is a kilovolt or two error? We ain't that special or writing any papers for peer review.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.
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