or "Vx1," and the frequencies of calibration should
With f representing the frequency of vibration (cycles
per second), V a v e r a g e as the average velocity of
be between 5 and 5000 CPS (or as limited by vibra-
tion transducer frequency response). Many calibra-
vibration (inches per second), and D as the peak-to-
tors are calibrated in terms of RMS velocity, whereas
peak displacement (inches), the equation reads:
the vibration meter is calibrated in terms of average
velocity. Assuming that sine-wave functions are being
used, the following simple conversion factors can
be used:
CHECK OF CIRCUITS. Before performing any meas-
Average inches/second = (0.90) (RMS
urements with the vibration meter, the following
inches/second)
steps should be taken:
RMS inches/second
= (1.11) (average
inches/second)
a. Turn the RANGE switch to the OFF position.
c. These examples may serve to clarify the use of
the conversion factors:
b. Leave the INPUT NETWORK and CHANNEL
selector switches in any position.
(1) Assume that a calibrator is used at a level of
0.5 RMS inches/second. To determine what the vibra-
c. The vibration transducer may be connected or
tion meter should read under this condition, use the
disconnected.
first formula given above:
d. Connect the meter ac power cord to 115 volts ac.
T u r n the OFF power switch to the on position.
Average V = (0.90) (RMS V) = (0.90) (0.5)
= 0.45 inches/second average
e. Perform the zero test by indexing the OPERA-
TION selector switch through the Vx1.0, Vx0.1,
(2) Alternatively, assume that it is desired to
Dx1.0, and Dx0.1 positions. A reading of not more
produce a vibration input corresponding to a full-
than two percent of full scale should be obtained,
s c a l e reading on the 0.5 inches/second average
indicating a noise level of less than two percent.
v e l o c i t y range of the vibration meter. Here the
problem is to determine the RMS velocity of the
f. Perform the calibrate signal test. Turn the OP-
shaker corresponding to this condition. This may be
ERATION selector switch to position C. Depress the
done using the second formula given above:
CALIBRATE SIGNAL control to operate. This con-
trol should adjust the meter indicator from one-third
RMS V = (1.11) (average V) = (1.11) (0.5)
to full scale. Set the meter indicator at 5 on the
= 0.555 inches/second RMS
lower scale and release the CALIBRATE SIGNAL
control, preparatory to step g .
1-44. OPERATING INSTRUCTIONS.
NOTE
1-45. GENERAL. When using Vibration Meter Type
1-117 with a compatible vibration transducer for
The CALIBRATE SIGNAL control taps a por-
measuring purposes, install the equipment as de-
tion of the filament supply voltage. The volt-
scribed in paragraph 1-30.
age regulator for the power supply distorts the
sine wave; however, the resultant wave is
1-46. The vibration meter may be set up to indicate
suitable for setting the gain of the first half
the value of the peak-to-peak amplitude of the vibra-
of the amplifier.
tion. This reading will serve as a check against known
acceptable limits for the equipment being tested. For
g. Perform the sensitivity control test. Index the
production work, monitoring checks at key points are
CHANNEL selector switch to each of its four posi-
usually sufficient to establish product acceptability.
tions. At each position, it should be possible to obtain
a full scale reading on the output meter by adjusting
1-47. If further details pertaining to the nature of the
the applicable channel SENSITIVITY control.
vibration are needed, the average velocity may also
be read directly from the meter. When the vibration
1-49. MEASUREMENT PROCEDURE.
consists of a single frequency, the frequency of vibra-
tion may be calculated from the reading of displace-
a. Make preliminary circuit checks and adjust-
ment and velocity by the use of the following equation.
ments set forth in paragraph 1-48.
