Geokon 4427, Instruction Manual, Page: 16 / 23

10
5. DATA REDUCTION
5.1 Displacement Calculation
The basic units utilized by Geokon for measurement and reduction of data from Vibrating Wire
Displacement Meters are “digits”. The units displayed by the GK-404 and GK-405 in position
“B” are digits. Calculation of digits is based on the following equation:
Digits =
�
1
Period
�
2
x 10
-3
Or
Digits
=
Hz
2
1000
Equation 1 - Digits Calculation
The magnitude of any movement is calculated from the following equation:
Displacement = D = (R
1
- R
0
) × F
Equation 2 - Displacement Calculation
Where;
R
0
is the initial reading taken at installation (Using channel B on the readout, the initial reading
should be around 3000 digits.)
R
1
is a subsequent reading.
F is the linear gauge factor (in mm or inches per digit), taken from the model 4427 calibration
report supplied with the equipment. Figure 9 in Appendix C.1 shows a typical model 4427 long
range displacement transducer calibration report.
For example:
If;
R
0
= 3083 digits
R
1
= 4228
F = 0.2223 mm/digit
Then;
Displacement = (4228 − 3083) × 0.2223 = +254.5 mm
Note that increasing readings (digits) indicate increasing extensions.
5.2 Temperature Correction
5.2.1 The Transducer Alone
The Model 4427 Long Range Vibrating Wire Displacement Transducer uses a Model
4400 displacement transducer which has a small thermal response; small enough that in
many cases correction may not be necessary. However, if maximum accuracy is desired