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Post by Deleted on Nov 10, 2008 7:13:14 GMT -8
How do I go about measuring gigaohm+ resistances with a conventional VOM?
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Post by Gary Lecomte on Nov 10, 2008 8:24:56 GMT -8
How do I go about measuring gigaohm+ resistances with a conventional VOM? Possibly I can give you a Simple Circuit to do this. But First I need to Know: 1) Is your meter a Digital VOM, Or an Analoge VOM? 2) Do you Know the "Ohm per Volt" Rating on your Meter? 3) Do you have a Stable, Voltage Power Supply? (100 Volts would be Good, But somewhat lower may also work.) Gary |
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Post by Deleted on Nov 10, 2008 17:50:31 GMT -8
Thanks
1) Is your meter a Digital VOM, Or an Analoge VOM? Triplett 2105 true rms DMM
2) Do you Know the "Ohm per Volt" Rating on your Meter? No
3) Do you have a Stable, Voltage Power Supply? I can build one. My power source from the
(100 Volts would be Good, But somewhat lower may also work.) wall is routed through a used hospital LIM.
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Post by Gary Lecomte on Nov 10, 2008 19:27:28 GMT -8
First you need to determine the Ohm per volt rating of your DVM.
If you don't have the manual, Look it up on the internet.
Or better yet, put it on the DC Voltage Range and using another DVM, Measure the Resistance from the probes.
I have a Fluke 87, True RMS meter.
But mostly I use a Fluke 73 for general measurements, and According to one manual, its 10 Meg, According to another, its 11 Meg, But measuring it, its 11.2 Meg.
With my Method of determining these High Value resistors, It is Important to have an Accurate reading of this probe resistance.
Let me know.....Gary
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Post by Gary Lecomte on Nov 11, 2008 10:23:38 GMT -8
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Post by Deleted on Nov 12, 2008 18:09:16 GMT -8
10.87 mohm
Thanks for the info
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Post by Deleted on Nov 13, 2008 7:14:33 GMT -8
A friend of mine gave me an old VTVM. It needs a new rectifier tube and capacitors but otherwise is good.
Since the input resistance on a VTVM is considered infinite ohms, would it be getter to use it instead?
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Post by Gary Lecomte on Nov 13, 2008 7:46:22 GMT -8
A friend of mine gave me an old VTVM. It needs a new rectifier tube and capacitors but otherwise is good. Since the input resistance on a VTVM is considered infinite ohms, would it be getter to use it instead? It is NOT Infinite Input Resistance! The Input goes to a Resistance Divider Network. I Have a Hewett Packard VTVM, That I use for Certan High Voltage Measurement, as it Far Less succeptable to Damage. |
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Post by Deleted on Nov 17, 2008 6:30:23 GMT -8
My Tripplet fancy dandy TRMS with all the bells and whistles
measures 10.8 megohms. My $12 "wally mart special" measures 10.2 megohms.
Most DMM's are probably made with FET inputs nowadays and and probably
rate in the 10 megohm range.
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Post by Gary Lecomte on Nov 17, 2008 8:24:33 GMT -8
Yes they are mostly in the 10 Meg range, But for this test it is Important to Know the Exact resistance.
Gary
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Post by Deleted on Nov 17, 2008 9:07:47 GMT -8
I know that. The point I was making is that with a cheap meter one can now make accurate readings.
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Post by Gary Lecomte on Nov 17, 2008 16:13:25 GMT -8
I know that. The point I was making is that with a cheap meter one can now make accurate readings. That still Depends on What your measuring? High Impedance circuit can still give considerable errors. Such as a 10 Meg resistor or higher value to the gate of a fet. Reguardless of weither its an old 20K Ohm Multimeter or a 10M ohm DMM, it always important to consider the circuit values and configuration. |
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