General Operation - Tektronix 1A2 Instruction Manual

Operating Instructions—Type 1A2
502 coaxial cable
with GR connectors
P6034 or
P6035, Probe
Y
ye _ - Y ge
X = GR Type 874
Connectors
Optional Items
'Select length which will move small reflection (due to
input Z of Type 1A2) out of area of interest.
*Used to reduce reflection by a factor of 4. Doubles
probe attenuation factor.
Used to reduce bulk on front of the Type 1A2.
GR Type 874-K
Coupling Capacitor
017-0028-00
Fig. 2-2. Using the P6034 or P6035 Probe with the Type 1A2.,
Variable Attenuator Balance Adjustments
If the VAR ATTEN BAL control of a channel is not properly
set, the position of a no-signal free-running trace will shift
vertically as the VARIABLE control is turned. If there is
a trace shift, set the VAR ATTEN BAL adjustment for each
channel as follows:
1. Set the Type 1A2 front-panel controls to the same
positions as in the Gain Adjustments procedure except the
AC-DC-GND switch must be set to GND and the MODE
switch to ALT.
2. Carefully adjust the Channel 1 VAR ATTEN BAL control
to a point where there is no trace shift as the Channel 1
VARIABLE control is turned back and forth through its full
range.
3. Carefully adjust the Channel 2 VAR ATTEN BAL control
to a point where there is no trace shift as the Channel 2
VARIABLE control is turned back and forth through its full
range.
4. Due to interaction between channels, repeat steps 2
and 3 until there is no further interaction.
GENERAL OPERATION
Either of the two channels of the Type 1A2 can be used
independently by setting the MODE switch to CH 1 or CH 2
and connecting the signal to be observed to the appropriate
input. Table 2-1 lists several input systems compatible with
the Type 1A2 input. Fig. 2-2 shows a block diagram of the
input when using the system outlined in Method 7 of Table
2-1. Figure 2-3 shows the X, and R curves for the Type 1A2.
Use of Probes
A conventional passive attenuator probe with a standard
42-inch cable lessens both capacitive and resistive loading,
but at the same time reduces sensitivity. The attenuation
introduced by the probe permits measurement of signal volt-
ages that would overscan the CRT if applied directly to the
Type 1A2. However, in applying high-amplitude signal volt-
ages to either the probe or Type 1A2, do not exceed their
maximum voltage ratings. When making amplitude meas-
urements with an attenuator probe, be sure to multiply the
observed amplitude by the probe attenuation factor.
To assure the accuracy of pulse or high-frequency measure-
ments, check the probe compensation. To make the adjust-
ment, proceed as follows:
1. Set the oscilloscope Amplitude Calibrator for a calibra-
tor output signal of suitable amplitude (at least 2 cm).
2. Place the MODE switch to the appropriate channel set-
ing (CH 1 or CH 2) to be used with the probe.
3. Touch the probe tip to the calibrator output connector
and adjust the oscilloscope controls to display several cycles
of the waveform.
4, Adjust the probe compensation for best square-wave
response as shown in the right-hand picture of Fig. 2-4.
NOTE
If a square-wave source other than the oscilloscope
calibrator is used for compensating the probe, do
not use a repetition rate higher than 5 kHz. At
higher repetition rates, the waveform amplitude
appears to change as the probe is compensated.
Thus, proper compensation is difficult. If the probe
remains improperly compensated, measurements
will be inaccurate.
2-3