[volt-nuts] Matched resistors

[George Atkinson]

At risk of being flamed for suggesting scrapping an instrument, selecting
the best pair from the K-V divider of an old Null Voltmeter may be an
option. A simple bridge with the test resistors in a heated oil bath and
the other pair kept constant will give an indication of match. Take care
not to mechanically or thermally stress the resistors when removing them.
The resistors will have been well matched originally and will be well aged.

Robert G8RPI.


On 17 July 2014 05:40, Frank Stellmach <frank.stellmach at freenet.de> wrote:

> Randy,
>
> resistor matched in T.C. are extremely expensive, as the manufacturer (or
> yourself) would have to select these from a batch of many samples.
>
> reistors with very small T.C. (<1ppm/K) would do the job also, but they
> also need to be stable over time, in shelf life opereation mode, i.e.
> P<10mW.
>
> That means, you need those hermetically sealed VHP202Z from Vishay, T.C.
> is typically < 1ppm/K and they are stable to < 2ppm over 5years. But they
> cost already 80€ each, depending on tolerance.
>
> I made a longterm observation of these and found these parameters
> confirmed.
>
> Frank
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