22
saaaa
represents polynomial coefficient A,
sbbbb
represents polynomial coefficient B and
scccc
polynomial coefficient C. The polynomial coefficients can be entered with a sign and decimal
point. The maximum number of digits, including sign and decimal point is 15. The entered value
will display to a maximum of five places to the right of the decimal point.
For the vibrating wire instruments (Gage Types 1-6), the basic formula for calculation of
displayed and stored values is:
Display
=
(CurrentReading
2
×
A) + (CurrentReading
×
B) + C
Equation 2 - Displayed Gage Reading using Polynomial Conversion
Geokon Model Gage Type
Description
4000
3
Strain Gage
4100
1
Strain Gage
4200
3
Strain Gage
4204
6
Strain Gage
4202/421X
1
Strain Gage
4300BX
1
BX Borehole Stressmeter
4300EX
5
EX Borehole Stressmeter
4300NX
1
NX Borehole Stressmeter
4400
1
Embedment Jointmeter
4420
1
Crackmeter
4450
1
Displacement Transducer
4500
1
Piezometer
4600/4651/4675
1
Settlement Systems
4700
1
Temperature Transducer
4800
1
Pressure Cell
4850
1
Low Pressure Piezometer
4900
1
Load Cell
4910/4911/4912
1
Load Bolts
Table 2 - Vibrating Wire Gage Types
NOTE: When using the Polynomial conversion method, the default reading units for a vibrating wire instrument is
the frequency squared multiplied by 10
-6
. For example, an instrument reading 3000Hz will output a value of “9.000”
when A is entered as “0”, B is “1” and C is “0”. However, typical calibration units for vibrating wire instruments are
frequency squared multiplied by 10
-3
. To adjust for this discrepancy between LC-2 expected units and calibration
units
multiply the A coefficient by 1,000,000 and the B coefficient by 1000. The A and B coefficients can be
found on the supplied calibration certificate.
The
C
coefficient should be calculated based on an actual field
reading.
The above multiplication is
only
necessary if the datalogger is being set up via text commands (see Section
2.6)
AND
the gage conversion is set for polynomial. When using LogView to set up the datalogger configuration,
the multiplication is performed by LogView. Refer to the appropriate sensor manual for more information on how to
calculate the
C
coefficient.