Tektronix 1A5 Instruction Manual page 20

Operating Instructions — Type 1A5
Gain switching in the output amplifier is controlled by
the VOLTS/CM control and is the only factor causing
changes in signal amplification in the 1 to 20 mV switch
settings. Combining gain switching with various attenuators
(in the front end of the Type 1A5 or in the Active Differential
Probe) provides for the wide range of less sensitive settings
of the VOLTS /СМ switch. The VARIABLE control affects the
amplifier gain and can be used to vary the sensitivity between
any of the VOLTS/CM calibrated settings.
VAR BAL and GAIN are used for balancing and gain
calibration of the amplifier.
The trace can be vertically controlled with the POSITION
knob. DC zero reference for signal measurement is estab ­
lished by grounding the signal inputs
trol.
The POSITION control should not be used to offset large
amounts of signal deflection when attempting to make
accurate observations. If the input signal causes the input
amplifier to operate in its maximum limits, distortion may be
introduced. Since the POSITION control affects only the
output amplifier, the distortion would be amplified and
the waveform would be unreliable.
Comparison Voltage feature should be used instead of the
POSITION control to eliminate DC levels at the input. A
less sensitive VOLTS/CM setting (larger deflection factor)
should be used to correct for excessively large AC deflec ­
tions.
TYPE 1A5 DIFFERENTIAL AMPLIFIER OPERATION
First Time Operation
The operating description which follows is designed to
assist in providing a CRT display, and to familiarize the
operator with the features of the instrument.
oscilloscope is used for the following instructions, but the
procedure will be essentially the same for any oscilloscope
with which the Type 1A5 is compatible.
Initial Setup
1. Insert the Type 1A5 into the oscilloscope.
into position with the securing knob.
2. Preset Type 1A5 controls as follows:
COMPARISON VOLTAGE (Vc)
AMPLITUDE
POLARITY
POSITION
AC-GND-DC (A Input)
AC-GND-DC (B Input)
DISPLAY
VOLTS/CM
VARIABLE
3. Set the oscilloscope Intensity knob ccw, preset con ­
trols for a free-running 0.5 ms/cm sweep.
oscilloscope and, after the time delay
increase the intensity until a trace appears on the CRT.
If no trace appears, obeserve the vertical position indicator
2-12
http://manoman.sqhill.com
and using this con ­
AC coupling, or the
A Type 544
Lock it
CCW to 0
0
Midrange
GND
GND
A-B
20 V
CAL
Turn on the
relay operates,
lights and move the STEP ATTEN BAL to bring the trace
to the center of the CRT.
Operation
Become acquainted with the operation of
by manipulating controls as follows. Observe
preciable change occurs in the sweep for any
as noted.
1. Rotate POSITION knob cw and ccw.
and down movement of the trace. Return
center.
2. With VOLTS /СМ knob
At .5 V/ cm position, pull the knob
to .2 and .1 V/ cm position. Return to
position. At 50 mV / cm position, pull the knob out
rotate cw to 20 mV and 10 mV positions. Return to 50 mV/
cm " knob in " position. " Knob out" positions will hereafter
be referred to as "Retained Range" positions.
3. Place A Input and В Input AC-GND-DC switches to
DC and then to AC positions.
4. Switch DISPLAY selector to A-Vc position,
to 20 mV and POLARITY to +.
5. Rotate AMPLITUDE clockwise to 0-0-6.
the trace shifts down to the — 3 cm position. Switch
ITY to — . Observe that the trace instantly moves up to
+3 cm position.
6. Change the DISPLAY control to Vc-B position. Observe
that the trace moves to the
ITY to +. Observe that the trace instantly moves
+3 cm position.
7. Return AMPLITUDE to 0. The trace should
CRT center. Place POLARITY to 0.
8. Rotate the VARIABLE knob through its
that the UNCAL lamp is lighted when
detented. Return VARIABLE knob to CAL.
lamp should go out.
9. Depress the DIFFERENTIAL
button. A Probe On light built into the button should
Depress the PUSH ON/OFF button two more
serve that the Probe On lamp extinguishes, then
Rotate the VOLTS/CM switch to 1 mV /СМ
the Probe On light stays on.
The light should go out. Note that the
button has no effect in the .5 V/ cm position
sensitive setting (higher VOLTS/CM setting).
WARNING
Voltages are present
connector jack whenever the Type 1A5
gized, regardless of the status of the
lamp.
Front Panel Adjustments
These adjustments must be accomplished each time the
Type 1A5 is placed in a different oscilloscope,
the Type 1A5
that no ap ­
setup except
Observe the up
the trace to CRT
"in", rotate it to each position.
out and rotate it cw
.5 V/ cm "knob
and
VOLTS/CM
Observe that
POLAR ­
— 3 cm position. Switch POLAR ­
to
return
range. Note
VARIABLE is
The UNCAL
PROBE PUSH
ON/OFF
light.
times. Ob ­
re-lights.
and note that
Switch VOLTS/CM to .5
PUSH ON/OFF
Or in any less
at the Differential Probe
is ener ­
Probe On
and should
in"
the
to
not
V.
®