EG&G ORTEC 442 Operating And Service Manual - Page 7

Browse online or download pdf Operating And Service Manual for Measuring Instruments EG&G ORTEC 442. EG&G ORTEC 442 16 pages. Linear gate and stretcher

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The ORTEC 442 may be operated outside the 401/402

Bin and Power Supply, using a power extension cable. Be

sure that the cable used accounts properly for the grounding

circuits recomrrtended in AEC standards of TID-20893

(Rev.). Both clean and dirty ground connections are

included to ensure proper reference voltage feedback into

the Power Supply and must be preserved by the remote

cable. Be careful to avoid ground loops when the module

is operated outside the Bin.

3.2 LINEAR INPUT CONNECTION

Linear input pulses can be furnished from any ORTEC

linear module of the 400 Series. These include amplifiers,

delay circuits, biased amplifiers, gates, and other pulse-

handling equipment. It is recommended that the 442 be

used ahead of the biased amplifier when both modules are

used in a system. The effective input range will be from the

adjusted discriminator level (-tO.1 to 1 V) up through-i-lO V.

When the linear input signals are furnished through a cable

more than 4 ft long (approximately), the input should be

terminated with the characteristic impedance of the cable.

This can usually be avoided by the use of shorter cable

lengths.

3.3. LINEAR OUTPUT CONNECTIONS

The shaped linear output pulses can be furnished into any

other ORTEC Series 400 linear module or directly into the

ADC input of a multichannel analyzer. It is important to

preserve the pulse shape and linear amplitude relationship

of the output, as it appears when accepted into subsequent

instrument modules. Either of two standard output imped

ances may be selected according to the type and length of

interconnecting cable and the input impedance of the instru

ment to which it is connected. The output is available

through a front panel connector, with an output imped

ance of less than 112, or through a rear panel connector,

with Zo = 9312. For most applications the 112 front panel

output connector can be used, with a short cable length, to

transfer the output signal into the (normally) high input

impedance of the next module.

When the output signals must be furnished through cable

lengths greater than approximately 4 ft, proper resistive

termination of the cable is required in order to preserve the

linear output pulses and prevent oscillations. Either of two

convenient methods can be selected for the 442 outputs,

when termination is required. One method is a series type

termination, using the rear panel 9312 Output connector

and an appropriate length of 9312 coaxial cable to transfer

the signal into the next module or instrument. The input

impedance of the next equipment wil l probably be of the

order of 100012 or more. The total amplitude of each

output pulse will be divided between the 9312 output

impedance of the 442 and the input impedance of the next

module; so a high input impedance is desirable when this

series-termination method is used. An alternate method

depends upon shunt termination at the remote end of the

cable. For this, use the front panel 112 Output connector

and whatever type of coaxial cable is desired. Then use a

BNC tee at the input to the next module to accept both the

cable and a BNC Terminator, selected to match the charac

teristic impedance of the cable when connected in parallel

with the instrument's input impedance. For convenience,

ORTEC stocks a limited quantity of BNC tee connectors,

and both 50 and 10012 BNC Terminators.

3.4. GATE INPUT

When Gate Input signals are required, they will be furnished

through the BNC connector on the front panel of the 442.

The function of an input pulse will be to trigger the 442

Linear Input gate for an adjusted Gate Period. The function

must be selected as either Coinc or Anticoinc by a rear

panel slide switch.

Gate Input pulses are effective when they rise through -)-3 V

for a period of at least 100 nsec. A standard NIM Slow

Logic positive pulse source may be used. The Gate Input

circuit is protected to ±25 V; so a wide variety of alternate

sources can also be used to initiate this control. When

operating in the Coinc mode, the Gate Period must

be triggered before the peak of the linear input pulse and

must be continued until after the peak. When operating in

the Anticoinc mode, the Gate Period must be triggered

prior to a discriminator response to the linear input and

must be continued until the discriminator has been reset.

No Gate Input is required if the front panel Normal/Gated

switch is set at Normal. Likewise, if the front panel switch

is set at Gated and the rear panel mode selector is set at

Anticoinc, a Gate Input pulse is not required except when a

linear input signal is to be rejected. Whan these switches are

set for Gated and Coinc, respectively, a linear input

pulse will be accepted only if it is accompanied by a time

coincident Gate Input pulse.

3.5. CONNECTION FOR BUSY OUTPUT

The duration of each Busy Output signal is from the time

that an input pulse peak is detected unti l the resulting

output pulse has been furnished and the input discriminator

has been reset. This identifies each period during which a

new input pulse cannot be accepted in the 442. This output

can be integrated externally to indicate the average dead

time.