Section 3 Operating Considerations; Information; Graticule; Grounding - Tektronix 2235 Instruction Manual

Section 3—2235 Operators
OPERATING CONSIDERATIONS
GENERAL OPERATING INFORMATION
GRATICULE
GROUNDING
The graticule Is Internally marked on the faceplate of
the crt to enable accurate measurements without parallax
error (see Figure 3-1). It Is marked with eight vertical and
ten horizontal major divisions. Each major division Is
divided Into five subdivisions. The vertical deflection
factors and horizontal timing are calibrated to the graticule
so that accurate measurements can be made directly from
the crt. Also, percentage markers for the measurement
of rise and fall times are located on the left side of the
graticule.
The most reliable signal measurements are made when
the 2235 and the unit under test are connected by a
common reference (ground lead). In addition to the signal
lead or probe. The probe's ground lead provides the best
grounding method for signal Interconnection and ensures
the maximum amount of signal-lead shielding In the probe
cable. A separate ground lead can also be connected from
the unit under test to the oscilloscope GND connector
located on the front panel.
1ST OR LEFT
VERTICAL
GRATICULE
LINE
RISE AND
FALL TIME
MEASUREMENT
PERCENTAGE
MARKERS
11TH OR RIGHT
VERTICAL
GRATICULE
LINE
7
CENTER
VERTICAL
GRATICULE
LINE
CENTER
HORIZONTAL
GRATICULE
LINE
4207-09
Figure 3-1. Graticule measurement markings.
SIGNAL CONNECTIONS
Generally, probes offer the most convenient means of
connecting an Input signal to the Instrument. They are
shielded to prevent pickup of electromagnetic Interference,
and the supplied 10X probe offers a high Input Impedance
that minimizes circuit loading. This allows the circuit under
test to operate with a minimum of change from Its normal
condition as measurements are being made.
Coaxial cables may also be used to connect signals to the
Input connectors, but they may have considerable effect on
the accuracy of a displayed waveform. To maintain the
original frequency characteristics of an applied signal,
only high-quality, low-loss coaxial cables should be used.
Coaxial cables should be terminated at both ends In their
characteristic Impedance. If this Is not possible, use suitable
Impedance-matching devices.
INPUT COUPLING CAPACITOR
PRECHARGING
When the Input coupling switch Is set to GND, the input
signal Is connected to ground through the Input coupling
capacitor In series with a 1-Mi7 resistor to form a pre-
charglng network. This network allows the Input coupling
3-1