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Operating Instructions-PG 506 (SN 8040000 & up)
Gain adjustments for oscilloscope amplifiers are usual
ly made at low levels, for example; at a 10 mV/div
deflection factor and a 50 mV signal from the PG 506. This
ratio corresponds to five major graticule divisions of beam
deflection.
If the gain of the oscilloscope amplifier system
is low, the indicated deflection will be less than five major
graticule divisions, for example; 4.8 major
division.
The
VARIABLE AMPLITUDE (OUT) control on the PG 506 can
then be used to increase the output amplitude until the
total deflection is exactly five major divisions. At this poi
nt,
the DEFLECTION ERROR readout will read 4.0% LOW.
Conversely, if the oscilloscope amplifier system gain is too
high, the indicated deflection on the crt will be above the
proper reference line, for example; 5.2 major divisions.
Using the VARIABLE AMPLITUDE control on the PG 506
to reduce the output ampliutde for exactly five major
divisions of deflection will produce a DEFLECTION
ERROR readout of 4.0% HIGH
.
For some oscilloscopes the deflection factor may not
be constant throughout the full vertical dimensions of the
graticule, due to compression or expansion nonlinearities.
To check for this type of nonlinearity; center a two
division display, then position the display to the top of the
graticule. Measure any deflection errors with the PG 506
VARIABLE AMPLITUDE control.
Next,
position the two
division display to the bottom of the graticule and measure
the deflection errors. These nonlinearities should be taken
into account when making measurements with full
graticule deflection, or with the crt trace positioned
towards the top or bottom graticule limits and using small
deflection factors.
Current Loop
One end of the Current Loop is grou nded and ter
minates a precision voltage divider. The direction of the
arrow is oriented for conventional current. To obtai n a
calibrated 5 mA from the Current
Loop,
set the mode
switch to STD AMPL position and the AMPLITUDE
control switch to the 100 V position. The DEFLECTION
ERROR readout should be off, or adjusted to read
0.0%.
The current signal can be either dc or
1
kHz square-wave
current, as selected by an internal switch.
PULSE GENERATOR MODE
General
In
order to ensure waveform fidelity when using the
Pulse Generator function of the PG 506, the following
precautions should be observed.
1. Use high quality 500 coaxial
cable,
connectors,
and terminations (where applicable). Make all connec
tions as tight and short as possible.
@
2. Reduce capacitive
and
inductive loads to a
minimum. Risetime degradation occurs with long cable
lengths.
3.
Minimum risetime and pulse aberrations are ob
tained with 500 loads and loads must be capable of
dissipating the power available at any output connector in
any operating mode.
4. The external equipment is assumed to have no dc
voltage across the
load
to which the PG 506 is connected.
If a dc voltage exists, the output amplitude from the
PG 506 will be in error by the amount of the dc offset. To
prevent dc-offset errors, couple the PG 506 outputs
through a dc blocking capacitor to the load. The time
constant of the coupling capacitor and the total resistance
in series must be long enough to maintain pulse
flatness.
High Amplitude Output
To use the PG 506 Pulse Generator system to produce
high amplitude square-waves, set the mode switch to
HIGH AMPL pOSition and connect external equipment to
the AMPL OUTPUT HIGH connector. Set the Period
controls for the period or frequency desired. The output
amplitude of this signal can be adjusted with the PULSE
AMPLITUDE control.
This signal can be used to adjust oscilloscope amplifier
input
capacitance,
attenuator compensation networks,
and other internal frequency compensation networks. The
AMPL OUTPUT HIGH signal is negative with respect to
ground,
with its risetime related to the riSing portion (from
a negative potential) of the waveform. Refer to Fig. 2-3.
The absolute peak-to-peak val ue of the square-wave is
determined by the load resistance and the setting of the
PULSE AMPLITUDE control. Table 2-1 lists the typical
amplitudes available when the PG 506 is terminated into
three different load resistances.
Table
2-1
OUTPUT LOAD VS. VOLTAGE OUT
HIGH AMPL OUTPUT
PULSE AMPLITUDE Control'
Termination
MIN
MAX
500 Load
0.3 V p-p
5.2 V p-p
6000 Load
1.9 V p-p
32.5 V p-p
1 MO Load
3.8 V p-p
~
60.0
V p-p
'Approximate amplitudes.
2-5
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