EG&G ORTEC 553 Посібник з експлуатації та обслуговування - Сторінка 9

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4. OPERATING INSTRUCTIONS

After the 553 has been connected into a system accord

ing to the installation information in Section 3, the

operating mode can be selected and the discriminator

thresholds can be adjusted as required for each appli

cation.

Figure 4.1 illustrates the timing relationships that will be

effective in the 553 for each of three possible input pulse

amplitudes. The first two pulses exceed the lower level

threshold without also exceeding the upper level, and the

third pulse exceeds both threshold levels. Superimposed

in each of these input pulses in Fig. 4.1 is an internally-

generated signal that rises to 50% of the input peak

amplitude and is stretched at that level. When the input

pulse decays through the 50% level, the CF discriminator

resets and, when delayed by a fixed interval, triggers the

SCA outputs if the analysis criteria have been satisfied.

The delay interval can be adjusted within the range of 0.1

to 1.1 (us using a front panel control. If the pulses of Fig.

4.1 were furnished to a 553 that was set for its Normal or

Window (differential) mode, time-significant SCA output

pulses would be generated for each of the first two input

pulses but none would be generated for the third be

cause its amplitude was greater than the upper level

threshold. If the pulses were furnished to a 553 that was

set for its Integral mode, a time-significant output pulse

pair would be generated for each of the three input

pulses. In either mode of operation, a ULD output will

result when the corresponding discriminator threshold is

exceeded by the input pulse amplitude.

The adjusted lower level threshold is furnished either

from the front panel Lower Level control or from an

external source through the rear panel LL Ref connector;

the alternate selection is made with the rear panel LL Ref

toggle switch - either Int for the front panel control or

Ext for the rear panel 8NC. In either case, the range is

from 0 to +10 V, measured from chassis ground, of the

input signal.

The adjusted upper level threshold is determined by the

setting of the front panel Upper Level or Window control

and by the front panel mode selector toggle switch.

When the switch is set at either Int or Nor, the range of

the variable control is from 0 to +10 V, measured from

chassis ground. When the toggle switch is set at Win, the

range of the variable control is 0 to +1 V, measured above

the adjusted lower level threshold.

For optimum time-significant SCA output timing, the

front panel Walk Adj must be trimmed to the combined

effects of the input shaping and its time constants and of

the expected dynamic range of operation. Using a dupli

cate of the minimum and maximum amplitudes for

shaped input pulses, set the control to provide the

minimum walk (variation of time of occurrence vs input

amplitude).

ULD

CF TRIGGER

Delay adjusted in range

of 0.1 to 1.1 jjs

—•

(DIFF) SCA POS OUT

(DIFF) SCA NEC OUT

(INT) SCA POS OUT

rL_

(INT) SCA NEG OUT

-Ih

■ih

Fig. 4.1. Timing Relationships for Input

and Output Pulses.