Electronics > Beginners
1V Reference @ 1ppm
spec:
Doesn't a Harmon divider just provide an accurate, and stable potential divider? If that is the case, doesn't that still leave the inaccuracies cause by the 10M Ohm load of the meter under test?
Doesn't the same problem of loading apply to all reference cells too? Presumably, they have a significant output resistance (in terms of 1ppm).
spec:
Can I ask a question of the experts in this field: When you are checking the precision of an instrument, what is the shortest time that the instrument could be connected to the reference source? I have a reason for asking. :)
Kleinstein:
A mercury reference cell would need a butter for a 10 M input impedance meter. This usually also applies to a Hamon divider, unless rather low impedance, which would call for self heating problems. However 6 Digit DMMs often have more than 10 M input impedance in the low voltage ranges.
tggzzz:
--- Quote from: spec on January 29, 2019, 04:32:04 pm ---Can I ask a question of the experts in this field: When you are checking the precision of an instrument, what is the shortest time that the instrument could be connected to the reference source? I have a reason for asking. :)
--- End quote ---
I would suggest "until the reading is stable and repeatable", where you have to supply the two obvious definitions.
Are you thinking of a mechanical multimeter and a Weston standard cell?
spec:
--- Quote from: tggzzz on January 29, 2019, 05:36:00 pm ---
--- Quote from: spec on January 29, 2019, 04:32:04 pm ---Can I ask a question of the experts in this field: When you are checking the precision of an instrument, what is the shortest time that the instrument could be connected to the reference source? I have a reason for asking. :)
--- End quote ---
I would suggest "until the reading is stable and repeatable", where you have to supply the two obvious definitions.
Are you thinking of a mechanical multimeter and a Weston standard cell?
--- End quote ---
My thought was to use a capacitor to lower the effective output impedance of a precision voltage divider but, in view of your and K's, remarks it is clear that a fair amount of time would be required to do the calibration so that idea goes down the tubes as only a film capacitor could be used. A supercap, which could allow sufficient time, would be too leaky, I think :)
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version