TM 9-4935-481-14-1
(c) During normal troubleshooting procedures it may be desirable to repeat certain logic events that would
only happen once in the course of an automatic run thus, a provision has been designed into the test start circuit that allows
the operator to continuously recycle the DMS logic back to Ts without waiting the full 14 seconds each time. The counter
inhibit(sec) run/hold/off switch provides the controlling signal, since it was anticipated that in most cases the clock inhibit
function would be used in the troubleshooting procedure. Regular UUT testing is done with this switch in the off position, but
when the switch is in run, the duration of the signals discussed in paragraph (5) above becomes dependent on the length of
time the switch is held in the actuated position. That is, release of the switch constitutes Ts, instead of Ts being generated by
the internal logic. At 14 seconds, the counter reset and trigger lines return to ground, as in the normal mode of operation.
d.
Tracker. (fig. 3-5)
(1) Purpose. Actual tracker operation is based on the focused image of the missile flare traveling in a circle
through the four quadrants of a silicon detector. The modulated output of each quadrant is then processed by the tracker
control signal comparator board (CSCB) to give the deviation (error) from line-of-sight. In order to check out these
processing circuits (CSCB), the detector out-puts must be simulated, which is the primary function of the DMS-D tracker
section.
(2) Related tracker function, boresight condition. When no error is present, the dot image will scribe a circle
whose center coincides with the center of the detector. This is considered a "boresight" condition, and the outputs of all four
detector quadrants will be equal. Since quadrant 1 is electrically connected to quadrant 3 (detector B output), and 2 to 4
(detector A output), the two signals will be complementary and of equal duration. Any such information must be related to a
time reference, however, and in this case the time base is a 20 Hz sine wave whose 0 crossing (in the positive direction)
coincides with the moment the dot image crosses from quadrant 4 to quadrant 1. The 20 Hz frequency is important because
the dot makes a complete circle over the detector in 50 msec, therefore, the sine wave is synchronized with the dot travel
and the crossing from quadrant 4 to 1 always occurs when the sine wave passes through 0. In addition to being a time base,
(a) Clearing of the DMS logic is performed prior to Ts by a 25 msec pulse that is fed to the direct clear
the sine wave is also used as a reference for determination of the amount of error present. The CSCB processes the
input of the timing flip-flops. When the pulse goes back to the "1" state, the logic is reset and enabled for operation. At this
detector A and B signals and generates sample pulses each time the dot image crosses from one quadrant to another. Since
exact time, the inhibit (ground) is removed from the clock reset line, and the base drive to a resistor switch (that had been
opposite quadrants are connected, two sample pulses per axis are generated for each revolution of the dot image. The
holding the trigger line at ground) is removed, causing the switch to turn off.
vertical error is determined by alternate sampling of the sine reference, and the horizontal error is derived from alternate
sampling of a cosine reference.
(b) Since the timing sequence of the MTS cannot be recycled back to Ts once it has begun, the DMS test
reset circuit is disabled for 14 sec in case the test start switch is inadvertently actuated while a run is in progress. After the
(3) Simulator operation, boresight condition. The sine and cosine references described above are generated in
14 second period, the clock reset and trigger lines are once again clamped to ground to hold the DMS and UUT in a state
the DMS-D along with the simulated detector out-puts. For the boresight condition under discussion, the detector circle and
preparatory to testing.
corresponding simulator outputs are shown in figure 3-6. Since a complete revolution over the detector is completed in 50
msec, the time spent in each quadrant will be
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