a suitable audio generator, and monitor the rms
the R37/R38 divider network. Check to be sure the
values of R37 and R23 are within 1% of the marked
input voltage with an accurate ac VTVM. Using a
test frequency of 500 cps, adjust the input level to
values.
obtain a full-scale reading with the OPERATION
c. Inject a signal of approximately 15 mv rms
selector switch set on Vx1.0. The rms input should
between pin 7 of V2 and ground. Adjust this signal
be 833 mv + 3% when the full-scale reading is obtained.
level until the vibration meter reads full-scale
exactly. (CALIBRATE SIGNAL control released; OP-
d. Set the OPERATION selector switch to Vx0.1
ERATION selector switch on Vx1.0 position; range
and again adjust the input for full scale. The rms
switch OFF.) Use a 500 cps test signal. The input
input should be 83.3 mv + 3% when the full-scale
signal level should be 15 + 0.3 mv rms at the time a
reading is obtained.
full-scale reading is obtained. If not, trouble exists
in the output/meter circuitry.
e. Set the OPERATION selector switch to Dx1.0
and adjust the input voltage for a full-scale reading.
1-61. DEFINITION OF TERMS AND FUNDAMEN-
The rms input should be 833 mv + 4% when the full-
TAL RELATIONSHIPS, SIMPLE HARMONIC
scale reading is obtained.
MOTION.
NOTE
If the test frequency is not exactly 500 cps
and the waveform is not purely sinusoidal,
readings will be incorrect when testing the
displacement ranges.
f. Set the OPERATION selector switch to Dx0.1
and adjust the input for a full-scale reading. The
rms input should be 83.3 mv + 4% when the full-scale
reading is obtained.
g. Repeating steps a through c should be adequate
to check the remaining channels.
1-60. LOCALIZING TROUBLES IF INTERNAL
CALIBRATION IS INACCURATE.
a. Connect an rms-reading ac VTVM between the
end of variable resistor R37 nearest switch S6 (the
CALIBRATE SIGNAL control microswitch) and ground.
With the CALIBRATE SIGNAL control depressed,
OPERATION selector switch on C, and the CALI-
BRATE SIGNAL control adjusted for full scale meter
reading, the measured rms voltage should be 833 mv.
If this reading is correct, shift the VTVM to read
the rms voltage between pin 7 of V1 and ground.
This reading should also be 833 mv rms when the
CALIBRATE SIGNAL control is released. If it is
not, the trouble exists in the V1 circuits.
b. If the reading obtained between the end of vari-
able resistor R37 and ground differs from 833 mv
rms (step a above), readjust the CALIBRATE SIG-
NAL control until this reading is obtained. Then shift
the VTVM to read between the junction of variable
resistor R37 and R23 and ground. This reading should
now be 15 0.3 mv rms. If it is not, trouble exists in
1-30
