Probes; Coaxial C Ables; External Triggering - Tektronix 2245A Operator's Manual

Operators Familiarization
P ro bes
A probe provides the most convenient way to connect an input signal to the
oscilloscope. The standard 10X probes supplied with the 2245A are shielded
against electromagnetic interference and have a high input impedance for
low circuit loading. The subminiature probe bodies are designed for probing
circuitry with closely spaced leads.
SCALE FACTOR SWITCHING. The VOLTS/DIV scale factors, displayed
on the crt, reflect the probe attenuation factor when Tektronix coded
probes are used.
OPERATING CONSIDERATIONS. To get the best waveform fidelity,
keep probe ground and signal leads as short as possible.
Misadjusted probe compensation can cause measurement error. Check
and adjust probe compensation whenever a probe is moved to a different
channel or oscilloscope. For the probe compensation adjustment proce­
dure, see Section 4 " Operator Checks And Adjustments" .
For detailed operating considerations and probe maintenance, see the in­
struction sheet supplied with the probe.

Coaxial C ables

Signal input cables can greatly affect the accuracy of a displayed
waveform. To maintain original frequency characteristics of the input sig­
nal, use only high-quality, low-loss coaxial cables. Coaxial cables must be
terminated at both ends in their characteristic impedance to prevent signal
reflections within the cable. Use suitable impedance-matching devices.
E xternal T rig g e rin g
Any of the four vertical channels in the 2245A can be used as a source of A
and B trigger signals. When you need a trigger signal source different from
the one derived from displayed signals, you can use any free vertical input
channel. CH 1 and CH 2 can " condition" a wide range of signals to produce
triggers over the full vertical deflection range from millivolts to hundreds of
volts. CH 3 and CH 4 have two basic attenuation factors (0.1 and 0.5 volts/
division), making them especially useful for triggering on and viewing digital
signal levels.
3-4
2245A Operators