a through h above. In each case, the appropriate
f. Set the INPUT NETWORK switch to OUT.
channel SENSITIVITY control should be used.
g. Adjust the proper channel SENSITIVITY control
1-42. CALIBRATION WITH STANDARD AC VOLT-
until the meter is at full scale indication. The fre-
AGE SUPPLY. To calibrate the vibration meter using
q u e n c y used must be between 5 and 5000 CPS.
a standard ac voltage supply, proceed as follows:
1-43. CALIBRATION USING A VIBRATION TABLE.
a. Determine the corrected sensitivity rating of the
Calibration of the vibration meter using a vibration
vibration transducer (s) to be used. From this figure,
table is the most conclusive method of calibration,
determine the vibration transducer output in milli-
and may be performed either with a standard vibra-
volts when operation is at 5 inches/second average
tion table equipped with standardized monitoring means
v e l o c i t y (or 50 degrees/second for torsiographs).
or with special calibrators equipped with an accurate
b. The calculation in step a above is based on an
i n t e r n a l velocity-sensing coil. In either case, the
a v e r a g e velocity figure; therefore, the calculated
channel SENSITIVITY control should be set to provide
vibration transducer output will be in average milli-
a reading equal to the known average velocity or
volts. Since most available voltage sources and/or
peak-to-peak displacement of the vibration transducer.
voltmeters are calibrated in RMS levels, correct the
calculated output level as follows:
a. DISPLACEMENT CALIBRATION: Displacement
can be accurately determined by optical or other
means. In calibrating the vibration meter by this
RMS millivolts = (1.11) (average millivolts)
technique, the OPERATION selector switch should
be set to "Dx0.1" or "Dx1." Note that the frequencies
c. Adjust a standard sine-wave voltage to the value
of calibration must fall within the following ranges:
calculated in b above and apply this voltage to the
vibration transducer input of the meter.
on "Dx0.1": from 50 to 1000 CPS
on "Dx1":
from 5 to 1000 CPS
d. Set the OPERATION selector switch to V x 1.
b. VELOCITY CALIBRATION: In this technique, the
e. Set the RANGE switch to 5.
OPERATION selector switch should be set to "Vx0.1"
