EG&G ORTEC 414A Руководство по эксплуатации и обслуживанию - Страница 8

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For the combination of series and shunt termination, use

the 93n output in the sending instrument for the cable

connection and use 9312 cable. At the input for the

receiving instrument, use a BNC tee to accept both the

interconnecting cable and a 100J2 resistive terminator. Note

that the signal span at the receiving end of this type of

receiving circuit will always be reduced to 50% of the signal

span furnished by the sending instrument.

For

your

convenience,

ORTEC stocks the

proper

terminators and BNC tees, or you can obtain them from a

variety of commercial sources.

4. OPERATING INSTRUCTIONS

4.1. FRONT PANEL CONTROLS

In/Out Toggle switches which allow the input signals to

the coincidence and anticoincidence circuits to be disabled

without the input coaxial cables having to be removed. The

circuit may be effectively changed to either a onefold,

twofold, or threefold coincidence circuit, as desired, by

operating these switches.

Resolving Time 10-turn potentiometer which determines

the 2t resolving time of the coincidence circuit; resolving

time is variable from 10 to 110 nsec.

4.2. TESTING AND OBSERVATION OF WAVEFORMS

Refer to Sections 6.1 and 6.2 for information on testing

performance and observing waveforms.

4.3. CONNECTOR DATA

Inputs A, B, and C The coincidence Inputs A, B, and C are

BNC connectors providing ac-coupled coincidence inputs.

Input impedance is greater than 3000J2. A positive 2-V

pulse

with

20-nsec

minimum width

is required. To

minimize reflections when driving from a low impedance

source into these connectors, a terminator equal to the

characteristic impedance of the driving cable should be

shunted from this connector to ground.

Input D The anticoincidence Input D is a BNC connector

providing

dc-coupled

anticoincidence input. Input

impedance is greater than 3000J2. A positive 2-V pulse with

20-nsec minimum width is required; longer pulse durations,

to dc, are acceptable and determine the anticoincidence

control period. To minimize reflections when driving from

a low impedance source into this connector, a terminator

equal to the characteristic impedance of the driving cable

should be shunted from this connector to ground.

Outputs Two separate, buffered

coincidence

output

signals are provided on BNC connectors. These signals are

greater than 5 V in amplitude and are 500 nsec wide. The

outputs are ac-coupled

with

less than

10S2 output

impedance.

Coincidence Output Test Points (TP1 and TP2) These

oscilloscope test points are for monitoring signals on each

coincidence Output BNC connector, to which they are

connected by a 470S2 series resistor.

Power Connector The Nuclear-standard module power

connector is an AMP 202515-5.

4.4. TYPICAL OPERATING CONSIDERATIONS

The Fast Coincidence circuit measures coincidence-from

the leading edge, or leading portion, of the input waveform.

The input signals are reshaped to a standard pulse width

from the leading edge. Figures 4.1 and 4.2 illustrate that

the input pulses can actually overlap in time but not satisfy

the coincidence requirements as dictated by the front panel

Resolving Time control.

1 1 rr

ny \

t i l l

- • *1-

TT^i

" III -

Fig. 4.1. Illustration of Actual Overlapping of Input Pulses

I and II, but Not During the Leading-Edge Resolving Time;

Trace III Illustrates No Output Pulse.

III

Fig. 4.2. Illustration of Input Pulses I and II Overlapping

During the Leading-Edge Resolving Time and Producing

Output Pulse III.