TM 55-4920-429-13
b. With the 2000 ohm valve load connected between the valve-drive outputs, amplifier output is +
3.299 volts dc. The gain of the amplifier is linear throughout its operating range. Output current is the
same for 1 volt of command plus 0 volt of feedback or for 0 volt of command plus 0.5 volt of feedback.
Valve-drive current varies inversely with the value of the command input resistor. The ratios of output
current to demand voltage for the three circuits are as follows:
Yaw: 1.556 ma per demand volt
Roll: 1.008 ma per demand volt
Pitch: 0.7747 ma per demand volt
c. A graph of command voltage and feedback voltage versus demand voltage is provided in fig. 1-3.
Several instantaneous values of command voltage and feedback voltage are plotted to indicate the cor-
responding instantaneous demand voltage.
1-24. Digital Multimeter CCA A2.
(See FO-7 and FO-8.) This circuit encodes input signals that are sent to digital display CCA A1. Card
CCA A2 includes analog and digital sections.
a. Analog. Analog inputs cause the meter to indicate in ac volts, dc volts, or K-ohms. There are four
ranges for each mode.
(1) Mode selection is controlled by relays K5 and K6. K5 and K6 are operated by input signals
OHM SEL– and AC SEL- gates U17-12, 13 and U17-4, 5. The gates provide decoding and control relay
operation. Without a logic ground at the mode inputs, the circuits measure dc voltage.
(2) The meter measures unknown voltage (VX) within the range of the reference voltage (Vref).
Range selection is controlled by relays K1, K2, K3, K4, K10 and analog multiplexer (4053B) U19X
and U19Y. Table 1-3 gives the status of relays K1 through K10 for each range in each mode. The table
also gives the Vref supplied to U20, pin 2, and the constant current supplied by VR2 to the unknown
resistance in K-ohms mode.
Table 1-3. Digital Multimeter Mode and
Range Select Data
RELAYS
CURRENT
MODE
RANGE
K1
K2
K3
K4
K5
K6
K7
K8
K9
K10
VREF
SOURCE
K OHMS
0 to 1.999K
2.0 to 19.99K
20 to 199.9K
200 to 1999K
ACV
o to 0.1999
0.2 to 1.999
2.0 to 19.99
20 to 199.9
DCV
0 to 0.1999
0.2 to 1.999
2.0 to 19.99
20 to 199.9
x
x
2.0V
1000 ua
x
x
x
2.0V
100 ua
x
x
x
2.0V
10 ua
x
x
x
x
2.0V
1 ua
x
x
0.2V
x
x
2.0V
x
x
x
2.0V
x
x
x
x
2.0V
x
0.2V
x
2.0V
x
x
2.0V
x
x
x
2.0V
X = relay energized.
1-13
