C4
TM 9-4935-481-14-1
-25 Vdc into 115 Vac, 400 Hz sine wave power.
A1 with its associated resistors forms a "current-summing" type of comparator, wherein the ratio of R1 to R determines the
(c) Performance testing of the TTS requires the use of 14 Vdc power, which is generated in the DMS-D
threshold (switch point) of the comparator. If, for example, R1 is 8% higher in value than R, the comparator will change state
by two series-pass dc regulators located next to the component board assembly. +25 Vdc is the input for regulator VRI,
when the signal exceeds the reference by 8%, Since R would then set the upper comparison limit at +8%, R2 could be used
whose output is adjusted (by means of a 2K potentiometer on the component board) to a nominal value of +16.50 Vdc to
1
to set the lower limit at -8%, thus forming an acceptance window about a nominal signal input. The signal and reference
compensate for voltage drops caused by a series blocking diode and wiring to the UUT. VR2 similarly regulates -25 Vdc
inputs must be of opposite polarity, however, which dictates a need for two sets of comparators; one set to evaluate a
down to -16.50 Vdc.
positive signal and the other for a negative signal.
(d) 25 Vdc and +5 Vdc power ground terminals El through E13 are ch ssis mounted next to the card file,
a
and are in electrical contact with the chassis. Analog (+13 V return) ground is the TB1 copper buss, which is made up of two
(b) The reference pulses occur at timed intervals and have a duration of 200 msec. An example of the
sections joined together and to the chassis at a single point on the front plate of the card file. The front panel ground lug E14
pulses used to evaluate the right stationary function curve is shown below:
is connected to TB1 and can therefore be considered a true signal ground monitor.
c.
Trainer. (fig. 3-4)
(1) Mode switch. Automatic and manual testing of the MTS is accomplished by programming the appropriate
UUT and stimuli signals through mode switch S6. Switch positions versus test function are as shown in table 3-3.
(a) Evaluation of the function curves and divide network is accomplished by comparing reference voltage
pulses to the monitoring set signals, and displaying go or no-go comparison results by means of the status lamps. The
voltage pulses are routed through the mode switch to the reference input of a window comparator, and the UUT signal is
applied through scaling resistors to the high and low inputs of the comparator, as shown below:
Actual sampling of the comparator outputs is done only during the last msec of each pulse, when the curve voltage would
nominally be the same as the pulse. For the above example, this would place the logic sample pulses at 0.201sec, 1.901sec,
and 10.101sec. If the high and low limit comparators are in a state corresponding to an in-tolerance condition at those exact
times, the go lamp will illuminate. Conversely, if either comparator showed the curve to be out of tolerance, the no-go lamp
would illuminate and remain on until reset by the test start switch. The go lamp indicates the status of each sample, thus it is
possible for both lamps to be on simultaneously if the curve fluctuated in and out of tolerance.
3-6
