EG&G ORTEC 552 Посібник з експлуатації та обслуговування - Сторінка 10

Переглянути онлайн або завантажити pdf Посібник з експлуатації та обслуговування для Вимірювальні прилади EG&G ORTEC 552. EG&G ORTEC 552 16 сторінок. Pulse-shape analyzer and timing single-channel analyzer

Друкувати сторінку

A Fraction 50%

,._ri

Channel B Trigger

"T"

Delay -

Channel B Neg Out

Channel 8 Pos Out,

J~L

I /»

Int mode only

Fig. 4.1. Timing Relationships for Input and Output Pulses

for Operation with Internal Strobe.

each of the first two input pulses but none would be gen

erated for the third pulse because it is too large to satisfy

the single-channel criteria. If the 552 is set for Integral

mode, the responses would be generated for the third

input pulse, as shown by the broken line output pulses.

For any mode of operation, the LL Out and UL Out pulses

are generated when the input pulse amplitude exceeds

the related discriminator level.

The adjusted lower-level threshold is furnished from

either the front panel Lower-Level control or an external

source that is furnished through the rear panel LL Ref

connector; selection of the source is made with the rear

panel LL Ref toggle switch. In either case, the range (for

an unattenuated input signal) is from Oto+IO V, measured

from chassis ground.

The adjusted upper-level threshold is determined by the

setting of the front panel Upper-Level control and by the

mode selector toggle switch. When the switch is set at

either Int or Norm, the range of the variable control is

from 0 to +10 V, measured from chassis ground. When

the switch is set at Win, the range of the variable control

is 0 to +1 V, measured above the adjusted lower-level

threshold.

When the rear panel Strobe switch selects Ext, operation

of the 552 is the same as it is for Int except for the time at

which a channel B output is made available. For this mode

of operation, an external strobe pulse must be furnished

after the channel B CF trigger time and before an auto

matic reset, and the channel B outputs are furnished

promptly at the strobe time. The time window, during

which the strobe can be effective, is from the trigger time

to 10 ms after the trigger. If no strobe is furnished within

the time window, the internal logic is reset without gen

erating an output through channel B.

For optimum time-significant outputs, each front panel

Walk Adj control must be trimmed for 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 each control to provide the minimum

walk for its respective channel; walk is the variation of

time of occurrence vs input pulse amplitude.

Using internal strobe, the decay shape of an input pulse

can be reconstructed. Use the following steps.

1. Select the same fraction for both channels of outputs,

and adjust the Delay control as desired.

2. Connect the channel A output to the Start input of a

time-to-pulse-height converter (TPHC).

3. Connect the channel B Neg output to the Stop input of

the TPHC.

4. Furnish the shaped input pulses to the 552 and meas

ure the time difference between the channel A and

channel B outputs. This is an accurate measurement of

the Delay time adjustment.

5. Switch the B-Fraction selector to each of its active

settings, 10% through 90%, and measure the time differ

ences at each level; use the adjusted Delay time to correct

each measurement.

Note; Do not use the Bl setting of the B-Fraction se

lector unless the input pulse is bipolar, since a zero

crossover is necessary to obtain a channel B output

when this selection has been made.

6. Plot the decay curve for the input pulses, using the

set of data obtained in step 5.

CIRCUIT DESCRIPTION

5.1.

GENERAL

Refer to block diagram 552-0101-B1 and schematic dia

gram 552-0201-S1, both included at the back of the

manual.

Figure 5.1 is a simplified block diagram of the 552 Pulse-

Shape Analyzer and Timing SCA. It shows that each input

pulse is furnished through an attenuator (attenuation

factors XI, X10, and X100). The resulting input pulse is

applied to each of four discriminators and its peak is also

stretched and attenuated for each of the two CF (con

stant-fraction) discriminators. The UL (upper-level) and

LL (lower-level) discriminators form the single-channel

analyzer. When the SCA logic is satisfied, it gates the

timing outputs of the two channels for their respective

outputs. Each of the four discriminators independently

triggers a response when the amplitude of its noninverted

input exceeds the amplitude of its inverted input. The

response of the UL and LL discriminators is latched until

an internal reset occurs. The stretcher for the constant-

fraction discriminators is also reset internally.

Reference levels for the UL and LL discriminators are set

independently for either Normal or Integral mode opera

tion. For Window operation, the threshold for the UL dis

criminator is based on the LL setting instead of ground.