Uncalibrated source to calibrated meter, then compare to UUT


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I would love some opinions on a practice I will describe here:

Uncalibrated voltage source

check setting versus calibrated 6.5 digit dmm, this is the nominal/true value

connect voltage source to unit under test dmm

test result is the unit under test value.

Is this an acceptable practice?
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i'm thinking along the lines of this.

Do you take a resistance box

connect to 3458 and get the up to date resistance values

use those values as the nominal

connect to unit under test that is only a 4 digit dmm

measure resistance versus the 3458 values (nominal).

that way you carry on the accuracy of the 3458 not the resistance box. you always have up to date values of the resistance.

this is not a current practice I am just asking.


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And the definitive answer is..... maybe.

Using "transfer standards" is an acceptable practice. But a lot depends on the devices being used.

Using a resistance box can work, but it depends on the stability of the output. It can vary with switch settings (repeatability), temperature, etc. It may be stable enough for your requirements, but you need to check first.

Transferring the accuracy using a fixed resistor works better than a resistor box because the error from the box's switching is eliminated - better stability.

Your first message concerning a voltage source has the same issue. You can accurately measure the voltage, but when you move the leads to another instrument has the output remained stable?

For voltage, current, RF power, temperature, etc. it is common to to comparison readings so that you can simultaneously see what you are sourcing and measuring. Simultaneous takes out the stability question.
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