Page 6 Hum Bug Reference Manual
Quest Scientific
INSTALLATION
The Hum Bug can be immediately put to use by inserting it into your recording system as
illustrated in the diagram below. Input and output connectors are located on the front panel and
the power switch is on the back of the unit. Insert the Hum Bug at any point in the chain of
instruments after the signal from your electrode or sensor is buffered and before the signal is
connected to your oscilloscope, computer, and/or tape recorder. The ideal location is after the
signal is fully amplified and any filtering is complete. This location will maximize the amplitude
of signals passing through the Hum Bug and will ensure that any electrical interference
accumulated along the signal path will be eliminated.
Turn on the Hum Bug and confirm that the green LED on the
Bypass Switch
is
illuminated. If not, press the
Bypass Switch
to toggle the indicator from red to green. Now
ensure that the indicator on the
Hold Switch
is also green. The Hum Bug is now in normal
operating mode.
During your initial evaluation of the Hum Bug it is a good idea to turn off any computer
monitors in the vicinity of your recording setup. This will eliminate possible confusion between
50/60 Hz noise and any additional interference associated with your monitors. See the section on
monitor noise for more details.
After an initial warm up period of approximately thirty seconds the Hum Bug will be
fully operational. It will then start adapting to whatever level of electrical interference happens
to be present in the input signal. As adaptation proceeds, noise in the output signal will
gradually decrease to minimal levels. During this period the
LED Indicator
on the front panel
will flash red to indicate that the noise replica is growing. As noise cancellation approaches
completion the rate of flashing will slow down and stop.
If the characteristics of noise in the input signal are not constant you may notice that the
LED Indicator
occasionally flashes. This indicates that the noise replica is either growing (red)
or shrinking (green) as the Hum Bug adapts to these changing conditions. On other occasions
the LED may remain solid green. This indicates that little or no electrical interference is present