Power line and low frequency pick up and noise – Transmille 1000-Series User Manual
Page 96
1000 SERIES OPERATION MANUAL
TRANSMILLE LTD.
Version 1.30
Page 96
Power line and low frequency Pick up and noise
These effects are most noticeable when using high resistance (100kohms and
above) and low current. All constant current sources have a very high output
impedance which will pick up noise just like the high value resistance. To reduce
pickup, use screened leads and try earthing the low side of the calibrator output.
For high value resistance it is essential that the cables insulation resistance will not
affect the accuracy. Most PVC cables will only have insulation resistance of around
10G
; this will give an error of 1% on the 100mohm output.
Low AC Current is particularly difficult, as the capacitance of screened leads will
shunt some of the current away.