1
ORTEC MODEL 567 TIME-TO-AMPLITUDE CONVERTER/SCA
1. DESCRIPTION
1.1. PURPOSE AND FEATURES
The ORTEC 567 Time-to-Amplitude
Converter/Single-Channel Analyzer (TAC/SCA)
measures the time interval between pulses to its
start and stop inputs, generates an analog output
pulse proportional to the measured time, and
provides built-in-single-channel analysis of the
analog signal. Additional gating modules are not
necessary with this unit, and timing experiments
requiring time ranges of 10 ns to 2 ms may be
performed with single-channel analysis, giving the
experimenter unparalleled flexibility in analyzing
random nuclear events that occur within a selected
time range. Time ranges from 50 ns to 2 ms are
provided via the front panel controls.
Separate gating (anticoincidence or coincidence) of
the start and stop inputs eliminates unwanted
events from time spectra via externally imposed
energy or timing restrictions. The 567 also
incorporates a built-in SCA inhibit feature in which
a TAC output is available only if the output pulse
falls within the window restrictions imposed by the
SCA. This feature may be switched in or out by a
convenient front panel switch.
In addition to its start and stop gating capabilities, after a valid start has been identified and after a
the 567 provides for a pulsed or dc-level stop pulse has arrived within the selected time
Reset/Inhibit signal via a front panel input range. The start input is disabled during the busy
connector. A Reset/Inhibit input signal terminates interval to prohibit pileup; the stop input is disabled
the conversion cycle and maintains a reset after the first accepted stop signal. An inhibit/reset
condition, inhibiting further TAC conversions for the circuit permits the operator to abort and cancel a
duration of the Reset/Inhibit pulse. A TAC output measurement after a true start has been
pulse which is in process at the time a Reset/Inhibit recognized. The input gate for the start circuit can
input is received will be completed before converter be operated in either an anticoincidence or a
reset is initiated. coincidence mode.
Valid Start and Valid Conversion outputs are Time ranges may be switch-selected for full-scale
provided on the rear panel for each accepted start intervals from 50 ns to 2 ms. Each time
and stop input respectively. The duration of the measurement is analog-stored in a low-loss
Valid Start output indicates the interval from the stretcher amplifier until a linear gate is opened by
accepted start until the end of reset. Valid either an internal or an external strobe. The internal
Conversion occurs from the end of the internal strobe can be obtained from either the start or the
delay after stop to the end of reset. stop input pulse and in either case occurs
The selectable TAC output width and variable reference. An external strobe can be used for a
delay, which are easily adjustable, further serve to prompt output at the strobe time provided that a
make the 567 a flexible instrument. The output of time measurement has been completed and reset
the TAC may be synchronized with the stop signal has not occurred. A rear panel switch can select
or an external strobe signal to further enhance its
versatility.
The SCA section of the 567 allows the
experimenter to place very specific time restrictions
on the timing spectrum. The SCA is operated in the
Window position where the upper-level
discriminator setting is added to that of the lower-
level discriminator. The SCA output pulse width is
equal to the time from the occurrence of the TAC
output until the end of the reset pulse or the end of
the TAC output. The synchronization of the SCA
output with the stop input virtually eliminates any
time walk in the SCA output.
All 567 inputs are printed wiring board (PWB)
jumper selectable to accept either negative or
positive NIM-standard signals. All inputs and
outputs are dc-coupled so that changing input count
rates will not hinder normal operation of the 567.
The TAC output should be connected to the dc-
coupled input of a multichannel analyzer (MCA) for
optimum high-count-rate performance.
1.2. OPERATION
Start-to-stop time conversion is accomplished only
automatically at a selected delay following the
To Next Page
Loading...