[volt-nuts] Reference Calibration Options - Solartron 7081andFluke 731B and 335A

[Charles P. Steinmetz]

Fred wrote:

>How do you know the standards drift and not the meters ? In worst 
>case they could drift the same amount in the same direction.

One needs to be able to trust something to be within a known 
tolerance band, based on either historical calibration data or a 
reliable manufacturer's guarantee (i.e., you bought it brand new and 
it is guaranteed to be within +/- x right now, within +/- y after a 
month, and within +/- z within one year).

Lacking either of these, one is feeling his or her way in the 
dark.  Even a used item, purchased and then calibrated, cannot really 
be trusted until it has been through several calibration cycles in 
one's own hands, because one never knows what indignities it may have 
suffered in its earlier life.  (The same applies to a 
newly-constructed reference, which has not been burned in to reach 
operating stability and also has just been through soldering trauma.)

Best regards,

Charles