88 • Reference Section
MultiClamp 700A Theory and Operation, Copyright 2000, 2001 Axon Instruments, Inc.
• Experiment. While hum can be explained in theory (e.g. direct pickup, earth
loops), in practice empiricism prevails. Following the rules above is the best start.
The final hum level can often be kept to less than 0.1 pA
p-p
. One technique that
should not be used to reduce hum is the delicate placement of cables so that a
number of competing hum sources cancel out. Such a procedure is too prone to
accidental alteration.