Tektronix Type 82 PLUG-IN Instruction Manual page 11

Operating Instructions—Type 82
(12) As nearly as possible, simulate actual operating condi-
tions in the equipment under test. For example, the equip-
ment should work into a load impedance equal to that which
(13) Consider the loading effect on the equipment under
test due to the input circuit of the Type 82. The input cir-
cuit can be represented by a resistance of 1 megohm
(=:1%) shunted by a capacitance of approximately 15 pico-
farads from dc to about 2 mc. (At frequencies above 2 inc,
the impedance gradually decreases.) If a few feet of un-
terminated shielded cable is used for coupling the signal to
the input circuit of the Type 82, the capacitance added by
the cable might be as much as 80 picofarads. Where such
resistive Gnd capacitive loads adversely affect operation of
the signal source, you might want to use the P6008 Probe
in the manner described next.
Use of Probes
The P6008 Probes, furnished with the Type 82, lessen both
capacitive and resistive circuit loading and, at the same time,
reduce sensitivity 10 times. The 10X attenuation introduced
by each probe extends the calibrated vertical deflection
factor of the Type 82 to 500 volts per centimeter Though
this means that higher amplitude signals can be displayed on
the crt within the graticule area, do not apply signals to the
probe that will exceed the maximum voltage rating of the
probe. (Refer to the P6008 Probe Instruction Manual for the
In general, do not exceed the 600-volt combined de and
peak ac rating of the probe or of the Type 82. If the Ty pe
will not attenuate the dc component of the signal because ac
capacitor of the Type 82. If the dc voltage rating of the
probe is exceeded, the dc input voltage rating of the Ty pe
To assure the accuracy of pulse and high-frequency
measurements, first check the probe compensation by using
the subsequent procedure. Then, when using the probe to
To compensate the P6008 Probe, proceed as follows:
1. Set the Amplitude Calibrator switch on the oscilloscope
for an output of suitable amplitude.
2. Hold the probe body and loosen the locking sleeve sev-
eral turns.
3. Touch the probe tip to the Cal. Out connector on the
oscilloscope.
the locking sleeve, continue to tighten the sleeve, as usual,
until it is hand tight. Then, as a fine adjustment, hold the
repetition rate higher than 5 kc. At higher repetition rates,
the waveform amplitude appears to change as the probe is
compensated, and you will not be able to compensate the
probe properly. If the probe remains improperly compen-
In some high-frequency applications or pulse work, the
frequency can be calculated more easily than the effect
caused by capacitive loading. As a solution to the problem,
use a P6034 or a P6035 probe. These probes have an in-
put capacitance of 0.6 pf (within a tolerance of 0.1 pf).
sistance versus frequency curves of the P6034 and P6035
probes as compared to the P6008. For further information
concerning the characteristics of the P6034 and P6035 probes,
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