Geokon 4200 Series Instruction Manual page 33

6. Combining the equations from steps four and five gives:
Substituting the given values for E, g, and ρ yields:
7.
8. In position A, (which displays the period of vibration, T) multiplied by a
6
factor of 10 :
9. Combining the equations from steps seven and eight gives:
10. The equation from step nine must now be expressed in terms of the strain in
the surface of the body to which the gauge is attached. Since the
deformation of the body must equal the deformation of the wire:
Where:
Ɛ is the strain in the body.
L
is the gauge length in inches.
g
11. Combining the equations from steps nine and ten gives:
Where: (for Model 4200)
L is 5.875 inches.
w
L is 6.000 inches.
g
12. Therefore:
13. The display on position "D" of the readout is based on the equation:
The squaring, inverting, and multiplication by the factor 3.30410
internally by the microprocessor of the readout so that the displayed reading in
position D is given in microinches per inch ().
Note: In the previous steps, T is seconds x 10
An alternative is: ε = 3.304 x 10
Where f is the frequency in Hz.
MODEL 4200 SERIES STRAIN GAUGES | THEORY OF OPERATION | 23
6
and ε is microinches per inch.
-3 2
f microstrain.
9
is all done