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Old 29th January 2011, 02:10 AM   #11
eyoung is offline eyoung  United States
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i'm thinking a #3 pencil lead turned on a lathe...

Regards, El
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Old 29th January 2011, 03:53 AM   #12
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You may find some cheap Chinese condenser microphone with broken capsule on ePay, it should have a pair of them: one for capsule polarization, second for gate leakage.
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Old 29th January 2011, 07:58 PM   #13
Doz is offline Doz  United Kingdom
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Originally Posted by Ty_Bower View Post
I still want to know why he needs such a thing...
Yep, spill the beans ... what's it for?
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Old 29th January 2011, 08:41 PM   #14
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i'm thinking a #3 pencil lead turned on a lathe...

Regards, El
1G resistors are about $3-4 Digikey or ebay. For homemade, pencil lead sounds like the most promising idea.

Test: hook scope (or other meter) across a 10M resistor and hook it in series to your 1G resistor, and hook the series pair to a source (battery, tone generator, power supply). Measure voltage across 10M to calculate current. Measure your source voltage. With V and I calcuate your R.


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Old 29th January 2011, 11:08 PM   #15
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John, that test will require one to know the impedance of the meter, as it will shunt the 10M resistor. Typically Flukes are about 10-11M. I think it would be more accurate to use say a 50VDC supply, so that about 0.5V across 10M. Some lab multimeters have 1G input impedance on low voltage DC ranges.

Ciao, Tim
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Old 30th January 2011, 12:11 AM   #16
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Originally Posted by trobbins View Post
John, that test will require one to know the impedance of the meter, as it will shunt the 10M resistor. Typically Flukes are about 10-11M. I think it would be more accurate to use say a 50VDC supply, so that about 0.5V across 10M. Some lab multimeters have 1G input impedance on low voltage DC ranges.
No problem if you have one already known 1G resistor. Connect it, set up input level to get some even reading on your meter, then play with a DIY one to get the same reading.
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Old 30th January 2011, 12:12 AM   #17
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Originally Posted by trobbins View Post
John, that test will require one to know the impedance of the meter, as it will shunt the 10M resistor. Typically Flukes are about 10-11M. I think it would be more accurate to use say a 50VDC supply, so that about 0.5V across 10M. Some lab multimeters have 1G input impedance on low voltage DC ranges.

Ciao, Tim
Good point. If it truly is 10M, then a 10M shunt is not needed at all. Just put the meter in series with the source and 1G resistor. I've used 10V to measure 1G before, so a 9V or 12V battery would work. Have used 1G, 10G, 100G. Gave away a 1T ohm resistor to a diyaudio member. The signal was too noisy to for me to know if I could actually measure that it was 1T ohms.


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Old 30th January 2011, 12:24 AM   #18
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No problem if you have one already known 1G resistor.
I think the next time I place an order with Mouser or DigiKey, I'm going to have to order one of these things. Just in case I need it some day...

SM106031007FE Ohmite Thick Film Resistors

Digi-Key - SM104FE-1000M-ND (Manufacturer - SM104031007FE)
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Old 30th January 2011, 12:32 AM   #19
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OP is in Denmark, I think but . . .

$5.50 w/expedited shipping five available

Click the image to open in full size.

ebay: New Vishay FHV-150E-1G00FK 1 GIG 1.5 WATT 1% 100 PPM thick film resistors


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Old 30th January 2011, 09:00 AM   #20
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I once saw a 10Gohm or so resistor which was encapsulated in a vacuum glass tube... To keep moisture out...
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