1
Fig. 1.1. Typical Timing Calibration Spectrum Using
256 Analyzer Channels.
ORTEC 462 TIME CALIBRATOR
1. DESCRIPTION
1.1. PURPOSE
The ORTEC Model 462 Time Calibrator generates
logic signals at precise time intervals that can be
used to test and calibrate a time-to-pulse-height
converter such as the ORTEC Model 437A, 447, or
457. The time base is a precision 100-MHz crystal-
controlled oscillator that is calibrated against WWV,
the National Bureau of Standards frequency, and is
temperature-compensated for accuracy throughout
the normal operating range of 0 to 500C. The time
intervals, their range, and their repetition rate are all
selectable in the Model 462.
Each output from the 462 consists of a pair of start
and stop pulses for the time-to-pulse-height
converter. Each pair of pulses is exactly Nintegral
time intervals apart, where Nis a multiple (2 or
more) of the selected period set on the 462. The
period selection consists of 11 binary steps from
10 ns to 10.24
µ
s. For example, if the period
selected is 40 ns, the intervals produced would
include 80 ns, 120 ns, 160 ns, 200 ns, 240 ns, etc.
Each timed interval is triggered by a random
generator,andthe462 circuit isarrangedsothatthe
probability that N= any multiple greater than 2 is
about equal, and the probability for N = 2 is about
doubled. The time spectrum that can be obtained
from the time-to-pulse-height converter then
consists of a series of sharp peaks at the multiples
of the selected period, and the first peak will have
about twice the count total as each of the other
peaks in the spectrum to simplify its identification
and ensure that the lower end of the spectrum has
not been biased off in the electronics.
Figure 1.1 is a time spectrum that was obtained
from a 462 output. The 462 PERIOD switch was set
at 80 ns (0.08
µ
s) for this spectrum. The first peak
in the spectrum, for 160 ns, has accumulated about
twiceasmanycounts as anyof theotherpeaks, and
peaks have been obtained for 160, 240, 320, 400,
560, 640, 720, 800, and 880 ns. Note that each
peak except the one for 800 ns has been
accumulated into just one of the 256 analyzer
channels that were used. The 800-ns peak has
been counted into two adjacent channels.
ARANGEswitch on the462permits selectionofthe
maximum multiple, N, for a given application and
must logically be set for an interval that is greater
than the selection with the PERIOD switch. The
RANGE switch selections are also binary steps
starting at 80 ns, with a maximum setting of
81.92
µ
s. In Fig. 1.1 the RANGE switch was set at
1.28
µ
s, and time intervals were produced that were
greater than the 880-ns maximum peak shown in
the spectrum. However, the range of the Model 457
Time to Pulse Height Converter was set for 800 ns
full scale, which accounts for the lack of any of the
longer time intervals in the spectrum even though
they were produced by the 462.
A RATE adjustment is included on the front panel to
control the average rate of the random generator
and thus control the average output rate of the start
and stop output pulse pairs. The range of this
control is from about 100 to 10,000 counts/sec.
An ON/OFF switch on the front panel, when set at
ON, permits operation to be gated through an
EXTERNAL ENABLE INPUT rear panel connector
if desired or to be continuous (without any gating).
An indicator on the front panel lights when the
instrument is actually producing the start and stop
output pulse pairs.
The 462 also includes a peak dispersion amplifier
that can mix semi-Gaussian noise with the analog
output of the time-to-pulse-height converter before
