Tektronix 585 Instruction Manual page 12

Operating nstructions — Type 585
nput Signal Connections
Input signals to the oscilloscope are carried to the input
connector of the Type 80 Plug-In Unit through the P80
high-frequency probe. The Type 585, Type 80 Plug-In Unit
and P80 Probe make up a basic DC to 95 megacycle system.
The gain of this combination is calibrated with a vertical
deflection of 0.1 volts per centimeter at the input to the
probe.
NOTE
A second basic wide-band system includes the
Type 82 Dual-Trace Plug-In Unit with a sensitivity
of 0.1 volts per centimeter. Special probes are
provided with the Type 82, permitting easy con ­
nection into any circuit.
volts per centimeter is available with slightly
reduced bandpass. The rest of this manual was
written for use of the Type 80 Plug-In and P80
Probe. Most of the conditions apply to the Type
82, except the input resistance and capacitance.
See the Type 82 Manual for additional details.
A third system using the Type 81 Plug-In Adapter makes
possible the use of all Tektronix Letter-Series plug-in units.
When using a Type 81 Plug-In Adapter Unit with a Type K
or Type L Plug-In Unit, the system bandpass is de to 3 db
down at 30 M c .
When using the Type 80 Plug-In Unit with the P80 Probe
in cases where the amplitude of the input signal is suffi ­
cient to deflect the spot off the screen, the vertical size of
the displayed waveform can be reduced to a usable level
by using one of the 5 fixed attenuators supplied with the
P80 Probe. The attenuators connect directly to the front
of the probe and provide attenuation factors of 2, 5, 10,
20, and 50 and vertical deflection factors of from 0.1 volt
per centimeter without an attenuator, to 5 volts per centi ­
meter.
The fixed attenuators supplied with the P80 Probe can be
used only one at a time. In cases where additional attenua ­
tion is required, a standardized attenuator is available that
permits the stacking of any one regular attenuator on a
standardized attenuator. The standardized attenuator pro ­
50-ohm Cable with
GR Connector, 017-501
GR to BNC Adapter, 017-024
Fig. 2-4. Accessories required to connect a 50 O system to the Type 80 Probe.
2-4
A higher gain of 0.01
50-ohm 10:1 Atten., 010-314
BNC to UHF Adapter, 103-032
vides attenuation of 10 when used alone. If the XI 0 Stand ­
ardized Attenuator is used with a regular 2-1 attenuator,
the total attenuation will then be 20. See the Accessories
section of this manual for part numbers and ordering in ­
formation.
Accuracy of the deflection factors of any of the attenu ­
ators or attenuator combinations can be checked by connec-
ing the attenuator tip to the CAL. OUT connector and com ­
paring the resulting deflection against the Amplitude Cali ­
brator voltage.
The calibrated vertical deflection factors and the graticule
markings permit accurate voltage measurements to be made
directly from the oscilloscope crt. The procedures for making
voltage measurements are described in the Applications sec ­
tion of this manual.
When connecting the oscilloscope to the signal source,
consider the loading effect produced by the probe on the
signal source. At low frequencies the input impedance of the
P80 probe is 100 kilohms which in most cases limits the
loading effect to a negligible amount. However, as the
frequency of the input signal is increased and approaches
the upper limit of the oscilloscope passband, the input im­
pedance of the probe drops to about 150 ohms. The load ­
ing effect of the probe under these conditions can be con ­
siderable, particularly when the input signal is connected
from a high impedance source. Loading may be sufficient to
adversely affect operation of the signal source.
Loading of the signal source can be reduced through use
of an attenuator head on the P80 Probe. However, this
also has the effect of reducing the vertical amplitude of the
displayed waveform. Consequently, the use of an attenu ­
ator head must be a compromise between reducing the
loading effect and reducing the signal amplitude.
way can the loading effect be completely eliminated. You
must consider this effect when evaluating information ob ­
tained from the oscilloscope. When observing signals from
low impedance sources, loading will usually be negligible.
To prevent reflection of high frequency waveforms and
resulting waveform distortion, all cables and high frequency
signal sources should be terminated in their characteristic
50-ohm Termination, 013-033
The Attenuator is optional.
In no
Type P80 Probe