SECTION III TECHNICAL PRINCIPLES OF OPERATION

TM 55-4920-430-13

SECTION Ill TECHNICAL PRINCIPLES OF OPERATION

1-12. Principles of Operation.

a. The test set consists of a large number of independent test circuits. These circuits share, a common

digital voltmeter display and internal power supply voltages to operate external valves and actuators.

There are common excitation voltage supplies for external position transducers and sensors. Signals are

developed to simulate feedback and position signals.

b. Test set circuits are functionally divided into 12 distinct sections. These divisions are indicated by

the grouping of switches and indicators on the test sets control panel. (See fig. 1-1. ) The switches and

indicators in each of these groups are listed and described in para 2-4. The manner in which they are

interconnected within the test set is illustrated in the schematic diagram. (See FO-1.) A detailed

description of test circuits are provided in para 1-13 thru 1-18.

1-13. AC/DC Voltmeter Circuitry. (See fig. 1-3.) Meter M2 is a self-contained multimeter. Test set

switching is used to select type of voltage (ac/dc) and range (.2, 2, 20, 200) for measurements. (See fig.

1-3.) A hold signal from sample and hold CCA A4 provides a preselected time interval between initial

application of an unknown input and the time that the signal is measured. Decimal point position is de-

termined by the setting of METER RANGE switch S6.

1-14. Pitch, Roll, and Yaw Integrated Lower Control Actuator (ILCA) Series Simulator Cir-

cuits. Circuit card A1 includes three circuits which simulate the servo valves and feedback devices of

the pitch, roll, and yaw ILCA. Three feedback outputs are developed, two self and one cross. A com-

bination of these outputs is selected by external switches to simulate the position feedback signal of the

actuator for a particular axis. Except for reference designations, the pitch, roll, and yaw circuits on the

card are identical.

a. Pitch ILCA Servo Simulator Circuit. (See fig. 1-4.)

(1) The impedance of the extensible link servo valve is simulated by resistors R1, R2, R3, and R5

and amplifier U18, with pin 14 of card A1 grounded through a 200-ohm resistance. This is the value of

the circuit sense resistor in the servo amplifier. The gain of amplifier U18 from pin 10 to TP1 is - 2 vdc/

ma.

(2) The output of amplifier U18 is fed to an integrator, made up of amplifier U17, resistor R4,

and capacitor C2. The integrator simulates the servo valve of the extensible link. Zener diodes VR1 and

VR2 simulate the limits of extensible link travel. The transfer function of the integrator is -20 vdc/

second. Output is limited to -12.5 to +12.5 volt dc by VR1 and VR2. Resistor R8 is selected to establish

the drift of the integrator at zero.

(3) Analog multiplier U16 simulates the extensible link position transducer. The gain of the mul-

10. When 13 volt ac is applied to pin 1, the voltage at Y1 is fixed at 5 volt

tiplier is (X1-X2) (Y1-Y2)

ac by voltage divider resistors R13, R14, and R15. Resistors R11 and R12 form a 3:1 voltage divider

vider which fixes the maximum input voltage to the multiplier at about 9 volt when integrator output is

maximum. Modulator gain from the integrator output to pin 32 is 0.76 x 0.5 vrms/vdc = -0.38 vrms/

vdc. The normal output at pin 32 is 15 vrms/sec-ma. This output controlled by the current input at pin

10, which is limited to about 4.75 volt rms or 6.7 volt peak. Resistor R14 is selected to control the gain

of the modulator. Resistor R17 is selected to establish the dc offset of U16 at zero.

1-6