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second method is series termination at the sending
end. The third is a combination of series and shunt
termination, where the cable impedance is matched
both in series at the sending end and in shunt at the
receiving end. The most effective method is the
combination, but termination by this method
reduces the amount of signal strength at the
receiving end to 50% of that which is available in
the sending instrument.
To use shunt termination at the receiving end of the
cable, connect the 1-
S
through 93
cable to the input of the receiving
S
instrument. Then use a BNC tee connector to
accept both the interconnecting cable and a 100-
resistive terminator at the input connector of the
receiving instrument. Since the input impedance of
the receiving instrument is normally 1000
more, the effective instrument input impedance with
the 100-
terminator will be of the order of 93
S
and this correctly matches the cable impedance.
4.1. PANEL CONTROLS
PULSE HEIGHT — The pulse height potentio-
meter controls the output pulse height from zero
volts to the maximum determined by the
attenuation factor toggle switches and the
termination load. This 10-turn potentiometer has a
calibration linearity of ±0.1%.
NORMALIZE — This 10-turn, 0.25% linearity
potentiometer varies the output pulse height
continuously over a 2.5 to 1 range (approximately)
to allow for normalization of the PULSE HEIGHT
dial setting. This control is ineffective when the
reference voltage switch is in the EXT position.
RELAY — This switch allows the internal relay to
be driven from either the ac line (AC FREQ.
position) or the internal oscillator (INT. OSC.
position). The frequency of the ac line will be 50 to
60 Hz, and the frequency of the internal oscillator
will be approximately 70 Hz. The RELAY switch has
a center OFF position which allows the relay to be
inoperative while leaving the power on to the pulse-
1
See Section 6.1 for test performance data on pulse waveforms.
output of the sending device
S
4. OPERATING INSTRUCTIONS
4
For series termination, use the 93-
sending instrument for the cable connection. Use
93-
cable to interconnect this into the input of the
S
receiving instrument. The 1000-
input impedance at the input connector represents
an essentially open circuit, and the series
impedance in the sending instrument now provides
the proper termination for the cable.
For the combination of
termination, use the 93-
instrument for the cable connection and use 93-
cable. At the input for the receiving instrument, use
a BNC tee to accept both the interconnecting cable
and a 100-
S
S
signal span at the receiving end of this type of
receiving circuit will always be reduced to 50% of
or
the signal
instrument.
,
S
For your convenience, ORTEC stocks the proper
terminators and BNC tees, or you can obtain them
from a variety of commercial sources.
forming circuitry. This position minimizes thermal
transients in the pulse forming network.
POLARITY — The polarity of the output signal will
be either positive (+) or negative (-) as determined
by the setting of the polarity switch. This control is
ineffective when the reference voltage switch is in
the EXT. position.
ATTENUATION FACTOR — The attenuation
switches control pi-attenuators in the attenuated
output line. The maximum attenuation is 2000:1.
The attenuation factor switches have an accuracy
controlled by 0.1% metal film resistors, and depend
upon the attenuated output being terminated in
100
.
S
RISETIME — The rise time of the attenuated
output signal is controlled by this 6-position switch.
The rise time marked on the front panel is elapsed
time for amplitude rise from 10 to 90% of the peak
value.
S
(or more) normal
S
series and shunt
output in the sending
S
resistive terminator. Note that the
span furnished by the sending
1
output of the
S
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