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FET voltmeter sought

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Peter Percival
Guest

Sat Mar 12, 2016 10:53 pm   



Suppose a fellow wished to buy a high input impedence voltmeter rather
accurate for low voltages (< 10v, say) but not expensive. Any
recommendations?

Reinhard Zwirner
Guest

Sat Mar 12, 2016 11:31 pm   



Peter Percival schrieb:
Quote:
Suppose a fellow wished to buy a high input impedence voltmeter
rather accurate for low voltages (< 10v, say) but not expensive. Any
recommendations?


What do you mean with "high"? Digital multimeters normally have an
input impedance of 10 MOhms; the lowest measuring range is 0.2 volts.

Best regards

Reinhard

Peter Percival
Guest

Mon Mar 14, 2016 6:40 pm   



Reinhard Zwirner wrote:
Quote:
Peter Percival schrieb:
Suppose a fellow wished to buy a high input impedence voltmeter
rather accurate for low voltages (< 10v, say) but not expensive. Any
recommendations?

What do you mean with "high"? Digital multimeters normally have an
input impedance of 10 MOhms; the lowest measuring range is 0.2 volts.


50 Mohms down to 0.01 volts. Is that too much to ask?
Quote:

Best regards

Reinhard


Phil Hobbs
Guest

Mon Mar 14, 2016 7:06 pm   



On 03/14/2016 08:40 AM, Peter Percival wrote:
Quote:
Reinhard Zwirner wrote:
Peter Percival schrieb:
Suppose a fellow wished to buy a high input impedence voltmeter
rather accurate for low voltages (< 10v, say) but not expensive. Any
recommendations?

What do you mean with "high"? Digital multimeters normally have an
input impedance of 10 MOhms; the lowest measuring range is 0.2 volts.

50 Mohms down to 0.01 volts. Is that too much to ask?


A 50 M precision series resistor (probably a series combination),
measuring on the microamp range. You have 1 pA resolution there, which
is 100 uV. You do have to watch the burden voltage, of course.

Cheers

Phil

Peter Percival
Guest

Mon Mar 14, 2016 7:19 pm   



Phil Hobbs wrote:
Quote:
On 03/14/2016 08:40 AM, Peter Percival wrote:
Reinhard Zwirner wrote:
Peter Percival schrieb:
Suppose a fellow wished to buy a high input impedence voltmeter
rather accurate for low voltages (< 10v, say) but not expensive. Any
recommendations?

What do you mean with "high"? Digital multimeters normally have an
input impedance of 10 MOhms; the lowest measuring range is 0.2 volts.

50 Mohms down to 0.01 volts. Is that too much to ask?


A 50 M precision series resistor (probably a series combination),
measuring on the microamp range. You have 1 pA resolution there, which
is 100 uV. You do have to watch the burden voltage, of course.

Cheers

Phil

Thank you.


JW
Guest

Mon Mar 14, 2016 7:39 pm   



On Sat, 12 Mar 2016 15:53:37 +0000 Peter Percival
<peterxpercival_at_hotmail.com> wrote in Message id:
<nc1e25$eli$2_at_news.albasani.net>:

Quote:
Suppose a fellow wished to buy a high input impedence voltmeter rather
accurate for low voltages (< 10v, say) but not expensive. Any
recommendations?


If you want fairly cheap:
HP 3478A has an input impedance of >100Gohm on it's 3VDC or less ranges.
HP 3456A has an input impedance of >100Gohm on it's 10VDC or less ranges,
but size is a bit large.

amdx
Guest

Sat Sep 24, 2016 5:25 pm   



On 3/14/2016 7:40 AM, Peter Percival wrote:
Quote:
Reinhard Zwirner wrote:
Peter Percival schrieb:
Suppose a fellow wished to buy a high input impedence voltmeter
rather accurate for low voltages (< 10v, say) but not expensive. Any
recommendations?

What do you mean with "high"? Digital multimeters normally have an
input impedance of 10 MOhms; the lowest measuring range is 0.2 volts.

50 Mohms down to 0.01 volts. Is that too much to ask?

Best regards

Reinhard



You could put a 40M resistor in series and divide the reading by 5.
0.002V x 5 = 0.01V So, I guess you would need a 4-1/2 digit multi meter.
Or is that 3-1/2?

Mikek

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