BASIC INSTRUMENT OPERATION
OPERATING CONSIDERATIONS
To ensure optimum measurement accuracy, the following
information should be considered before operating the
instrument.
Signal Connections
Generally, probes offer the most convenient means of
connecting an input signal to the instrument Oscilloscope
probes are shielded to prevent pickup of electrostatic inter
ference. The supplied 10X probe offers a high input im
pedance, which minimizes circuit loading and allows the
circuit under test to operate very close to normal conditions
providing accurate measurements. Conversely, it also at
tenuates the input signal amplitude by a factor of 10.
Coaxial Cables
Cables used to connect signals to the input connectors
have a considerable effect on the accuracy of a displayed
waveform. To maintain the original frequency character
istics of an applied signal, high quality, low loss coaxial
cable should be used. Also, the cable should be terminated
at both ends in its characteristic impedance. If this is not
possible, use suitable impedance matching devices.
Grounding
The most reliable signal measurements are made when
the 305 and the unit under test are connected together by a
common reference (ground) lead in addition to the signal
lead or probe. The ground strap on the probe provides the
best ground. Also, you can connect a ground lead to the
chassis ground connector located on the right side panel
of the instrument.
Graticule
The graticule is internally marked on the faceplate of
the crt to provide accurate measurements without parallax.
The graticule is marked with eight vertical and ten horizon
tal major divisions. In addition, each major division is divid
ed into five minor divisions. The vertical deflection and
horizontal timing are calibrated to the graticule, so accurate
measurements can be made directly from the crt.
REV A SEP 1979
305 Operators
15
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