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Operating Instructions— Type 1A1
introduced by the probe permits measurement of signal
voltages that would overscan the CRT if applied directly
to the Type 1A1. However, in applying high-amplitude
signal voltages to either the probe or Type 1A1, do not ex
ceed their maximum voltage ratings. When making ampli
tude measurements with an attenuator probe, be sure to
multiply the observed amplitude by the probe attenuation.
To assure the accuracy of the pulse or high-frequency
measurements, check the probe compensation. To make the
adjustment, proceed as follows:
1. Set the oscilloscope Amplitude Calibrator for a cali
brator output signal of suitable amplitude.
2. Place the MODE switch to appropriate channel setting
(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. 2-5.
NOTE
If a square-wave source other than the oscilloscope
c a lib ra to r is used fo r compensating the probe, do
not use a repetition rate higher than 5 kHz. At
higher repetition rates, the w aveform amplitude
appears to change as the probe is compensated.
Thus, proper compensation is d ifficu lt. If the probe
remains im properly compensated, transient and
frequency response o f the system w ill be poor
and measurements w ill be inaccurate.
INPUT SELECTOR Switch
To display both the DC and AC components of an applied
signal, set the INPUT SELECTOR switch to DC; to display
only the AC component of a signal, set the INPUT SELEC
TOR switch to AC.
In the AC position of the switch, the DC component of
the signal is blocked by a capacitor in the input circuit.
The input time constant of the input circuit is about 0.1 sec
ond and the low-frequency —3 dB point is below 2 Hz.
Some drop in duration response (droop) exists even when
Fig. 2 -4 . Type 1A1 nominal input resistance and capacitive reactance vs frequency at any position of the VOLTS/CM switch. Note that
input impedance (R and X< ) decreases as frequency increases.
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2-5