On Fri,8/5/2016 3:19 AM, Rob Atkinson wrote:
Balanced line operators need a pair of identical thermocouple amp
meters arranged so as to be easily inserted in the line to measure the
current on each side simultaneously.
Identical is the key word here. Remember that the coupling of noise in a
system is due to the imbalance, which is the DIFFERENCE of two currents
that are quite close in amplitude. Thus, very small errors in the
measurements of the two currents result in a large error in the common
mode current in dB. Those errors include the precision of the match
between the two ammeters, the precision to which they can be read, the
difference, at the measurement frequency, of any stray L and C in the
coupling to the two thermocouples.
73, Jim K9YC
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