Canberra 2015A, Руководство пользователя

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When the SCA MODE jumper plug (J6) is in the SCA position the timing monostable
(A7a) is now triggered from the LLD discriminator. The SCA OUTPUT will be gener-
ated as before, however the timing information is lost. The timing monostable trigger
point is now dependent on the AMP OUTPUT signal rise time and LOWER LEVEL
(E) discriminator setting.
Disc Output
Depending on the DISC A (J7) jumper plug position, the DISC OUTPUT can provide
LLD or ULD information. With the DISC A jumper plug (J7) in the LLD position,
DISC monostable A11b is triggered from the lower level discriminator through pulse-
former Al2a and A6a. Monostable A11b generates a 500 nanosecond pulse every time
the AMP OUTPUT signal crosses the LOWER LEVEL (E) discriminator threshold. If
the DISC A jumper plug (J7) is in the ULD position, monostable A11b is triggered
through inverter A12c from the WINDOW discriminator. Monostable A11b is in-
verted by Q23 with Q24 and Q25 forming a pair of complementary low OUTPUT im-
pedance emitter followers. The DISC OUTPUT is nom5 volts (unterminated);
however will increase to approxi8 volts (unterminated) if resistor R
A
(3.9k
ohms) is removed.
Lower Level (E) Threshold Circuit
The raw +12 volts is attenuated by a 3:1 divider network composed of R114, RV4, and
RV5. RV4 is calibrated so that 4 volts appears across RV5. Some fraction of this volt-
age is picked off, using the LOWER LEVEL discriminator control (RV5), and buf-
fered by the high input impedance amplifier A15. The, OUTPUT of A15 provides the
reference voltage for the LOWER LEVEL discriminator A13.
When the DISC B jumper plug (J8) is connected to the IN position and the LLD
jumper plug (J5) connected to the EXT position, control of the LOWER LEVEL (E)
discriminator is now possible by an external voltage source (0 to +10 volts) through
the rear panel DISC BNC.
The external sweep input voltage is attenuated by the 2.5:1 divider network R167 and
R168. This voltage is buffered by amplifier Al 5 providing an external reference volt-
age for the Lower Level discriminator A13. RV7 calibrates the low end of the
LOWER LEVEL (E) adjustment range.
35
SCA Section