ORTEC 420 - Operating Procedures; Front Panel Control Functions

4-1
4. OPERATING INSTRUCTIONS
4.1 Front Panel Control Functions
"E" DISC.
The function of the "E" (or energy) discriminator is the some as with any discrimi
nator, i.e., to prevent discriminator triggering by those signals which are below
the selected threshold. The threshold range of this discriminator is from approxi
mately 100 millivolts to 10 volts direct reading on the dial.
"AE" DISC.
The "AE" discriminator forms the upper level of the single channel analyzer. The
dial of this discriminator reads the difference in voltage or energy between the
"E" discriminator and the upper level; therefore, it reads "AE." Since this forms
the upper level of the single channel analyzer, the output from this discriminator
is placed in anticoincidence with an output from the lower level or "E" discrimi
nator so that when triggered, there is no output. Therefore, to obtain an output
from this unit a signal must be bigger than the "E" setting but less than "E"
+ "AE." (When the Differential/Integral (DIFF./INT.) switch is set to the INT
position, the "AE" function is disabled, and the unit becomes an integral dis
criminator which is controlled by the "E" dial.)
Delay Control
When the bipolar signal passes from a positive to a negative value, or when the
unipolar signal recrosses the "E" discriminator setting (depending upon the selec
tion of unipolar or bipolar operation by means of switch SI), a logic signal to be
used for timing or counting operation is generated. The delay control allows the
output logic signal to be delayed in time from this reference time, to+ a constant
propagation delay, over a range of 0 to 1000 nanoseconds. This delay is con
tinuously variable by means of a 10-turn potentiometer.
UNIPOLAR/BIPOLAR Switch (SI)
Switch SI selects the mode of operation of the timing unit, and should be set to
correspond to unipolar or bipolar signals at the input; i.e., if the input signal is
a singly differentiated pulse this switch should be in the UNIPOLAR position, and
if the input signal is a bipolar signal the switch should be in the BIPOLAR posi
tion. Precise timing is available only when the signal is a bipolar signal.