The purpose of this lab was to calibrate a vibration meter using an electrodynamic exciter and a vibration pickup. This experiment for a Mechanical Measurements Lab was intended to validate that our calculated data was within reasonable accuracy to that of the vibration meter.

1. Vibration Meter Readout Calibration
Paul Gibson
John Winchester
Fahad Khan
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2. Table of Contents:
Purpose 3
Abstract 4
Background 5
Apparatus 7
Diagram(s) 8
Procedure 9
Results 10
Appendix 15
2

3. Purpose:
Calibrate a vibration meter using an electrodynamic exciter and a
vibration pickup. The standard for displacement will be a ‘V’ scope.
The standard for frequency will be an oscilloscope (time). Compare ‘V’
scope and oscilloscope derived values of displacement, velocity and
acceleration with meter values.
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4. Abstract:
Vibration occurs if displacement and time are continuous with a
repetitive nature. Vibration is not an event that occurs one time;
furthermore, it is not an event that may show vibratory characteristics
that slowly decay with time. The latter case would be an example of a
shock. Velocity, acceleration and displacement are not examples of
vibration.
Vibration was measured in this lab using a vibrating wedge; it
is nothing more than a piece of paper with a scale drawn on it. This
wedge is taped to the vibrating member and used to measure the
amplitude of motion. A picture of this device is provided on the next
page. Both measured gravitational force and measured velocity in sec
in
were compared with calculated values using predetermined formulas. The
results of these comparisons are provided in tabular form in the
results section of this report.
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5. Background:
As everyone already knows, there are many different types of
motion. Some of the more common forms of mechanical motion are
velocity and acceleration. Vibration is a special kind of motion
however. Vibration occurs if displacement and time are continuous with
a repetitive nature. Vibration is not an event that occurs one time;
furthermore, it is not an event that may show vibratory characteristics
that slowly decay with time. The latter case would be an example of a
shock.
Although shock and vibration are not similar types of motion they
do share several characteristics, they both, possess frequency,
amplitude and some kind of waveform. Measuring of both shock and
vibration usually consists of a common method of using time-based
relationships for velocity, acceleration and displacement.
Assuming that the amplitudes of motion are greater than about
32
1
inches than a rather simple, almost archaic tool known as a vibrating
wedge may be used to measure the amplitude. Literally, all this
measuring device is a piece of paper or other thin material attached
the vibrating apparatus. This wedge has a scale drawn on it that is
used to measure the amplitude. As vibration occurs, the wedge moves to
two extreme positions, resulting in a double image that is very
defined. The center of the image, which is shown in the diagram below
as ‘X’, appears noticeably darker (as it pertains to this diagram. Our
actual wedge was not exactly this) than the surrounding area of image.
You can obtain a measurement of amplitude by noting the location of
this center position; it is at this point where the width of the wedge
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6. is equal to twice the amplitude. A diagram of this simple device and
how it operates is provided below.
This lab also used an electronic meter to measure the mils, sec
in ,
and gravitation force. Both measured gravitational force and measured
sec
in were compared with calculated values using predetermined formulas.
The formulas used for this process are below.
( )
frequencyf
amplitudedoubleDA
sec
=
=
=





fDA
in
velocity π
6

7. ( ) ( )
frequencyf
amplitudedoubleDA
051.0 2
=
=
= fDAgonaccelerati
7

8. Apparatus:
The equipment needed for this experiment is as follows (Refer to
figure):
1. Oscilloscope
2. Vibration Meter
3. Digital Counter
4. Oscillator
5. Power Amplifier
6. Shaker
The oscilloscope is manufactured by Hitachi. The model number is
VC-6224. The serial number is 1120276.
The vibration meter is manufactured by Vitec. The model number
is 654. The serial number is 14870-qm.
The Oscillator is manufactured by Hewlett Packard and is model
number HP 209.
The manufacturers of the power amplifier and the digital counter
are unknown. The model number of the power amplifier is 2125MB.
The shaker is produced by MB electronics and its model number is pm 25.
The serial number is 372.
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9. Diagrams:
9

10. Procedure:
1. Setup the apparatus as shown in the diagram above.
2. Construct a vibrating wedge to measure displacement. Its
dimensions should be 2 inches by 150-200 thousandths. Place
the wedge on the shaker and be sure it is horizontal.
3. Set the frequency on the HP oscillator to 20 Hz. Confirm this
setting on the oscilloscope. Turn up the power to maximum on
the power amplifier.
4. Slowly turn up the gain on the HP oscillator, and you will see
the shaker will begin moving. Turn up the gain until the
displacement on the vibrating wedge reads 0.04 inches.
5. Take the reading for mils, g’s and velocity from the vibration
meter.
6. Raise the gain to produce the following displacements: 0.08,
0.12, 0.16, and 0.2. Take the same readings as above at each
increment and record all data.
7. After going through all of the set displacements for 20 Hz,
follow the same procedure for 30 Hz, 40 Hz, 50 Hz, 60 Hz, and
80 Hz. Record all data.
8. Plot the following data on charts: Vibrating Wedge
displacement versus Vibration meter displacement, Calculated
velocity versus Vibration meter indicated velocity, and
Calculated acceleration versus Vibration meter indicated
acceleration.
10

11. Results:
The following tables show all the data we collected for this
experiment. Some of the data reads maximum. This is where either the
power amplifier would shut off, or the vibration meter would not give a
reading. The remaining data was linear, as it should be. This
confirms that the vibration meter confers with our calculated data, and
is measuring data with reasonable accuracy and precision. There is one
area where the calculated data and measured data were not relating very
well. This was for a frequency of 30 Hz. This could have occurred
because of calculation errors or because of lack of familiarization
with the vibration meter.
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12. Frequency Wedge Scope Meter Calculated Meter Calculated Meter
Displ. Frequency Displ. Velocity Velocity Accel. Accel.
20 0.04 20 49.7 2.50 2.9 0.81 1.00
0.08 20 81.8 5.03 5.0 1.63 1.70
0.12 20 117.5 7.54 7.3 2.40 2.45
0.16 20 161.4 10.05 10.0 3.26 3.50
0.20 20 188.2 12.57 11.7 4.08 4.10
30 0.04 30 49.9 3.77 6.1 1.84 3.80
0.08 30 78.8 5.03 9.6 3.67 6.10
0.12 30 114.2 11.31 13.8 5.51 8.80
0.16 30 156.5 15.08 14.2 7.34 6.80
0.20 30 198.2 18.85 18.0 9.18 8.70
40 0.04 40 53.9 5.03 6.5 3.26 4.10
0.08 40 86.1 10.05 10.4 6.53 6.60
0.12 40 126.6 15.08 15.3 9.79 9.70
0.16 40 165.3 20.11 20.0 13.06 12.60
0.20 40 max 25.13 24.7 16.32 15.60
50 0.04 50 42.7 6.28 7.4 5.10 6.00
0.08 50 84.8 12.57 13.0 10.20 10.40
0.12 50 123.0 18.85 18.8 15.30 15.00
0.16 50 162.8 25.13 25.2 20.40 20.10
0.20 50 max 31.42 31.2 25.50 25.00
60 0.04 60 59.3 7.54 10.9 7.34 10.50
0.08 60 91.3 15.08 17.0 14.69 16.20
0.12 60 127.3 22.62 23.4 22.03 22.50
0.16 60 max 30.16 max 29.38 max
0.20 60 max 37.70 max 36.72 max
80 0.04 80 47.5 10.05 11.7 13.06 15.00
0.08 80 max 20.11 max 26.11 max
0.12 80 max 30.16 max 39.17 max
0.16 80 max 40.21 max 52.22 max
0.20 80 max 50.27 max 65.28 max
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13. Wedge Displacement vs. Meter Displacement
0.00
0.05
0.10
0.15
0.20
0.25
0.0 50.0 100.0 150.0 200.0 250.0
Meter Displacement (mils)
WedgeDisplacement(inches)
20 hz
30 hz
40 hz
50 hz
60 hz
80 hz
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14. Calculated Velocity vs. Meter Velocity
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0
Meter Velocity (in/sec)
CalculatedVelocity(in/sec)
20 hz
30 hz
40 hz
50 hz
60 hz
80 hz
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15. Calculated Acceleration vs. Meter Acceleration
0.00
5.00
10.00
15.00
20.00
25.00
30.00
0.00 5.00 10.00 15.00 20.00 25.00 30.00
Meter Acceleration (g's)
CalculatedAcceleration(g's)
20 hz
30 hz
40 hz
50 hz
60 hz
80 hz
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16. Appendix:
The appendix section follows from here on.
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