Campbell Scientific CR5000 Measurement and Control Module - Manual (Page 199)

Section 8. Processing and Math Instructions
8-27
4 Full bridge strain gage, 2 gages parallel to
+ε
, the other 2 parallel to
−ε
:
µε =
−
10
6
V
GF
r
5 Full bridge strain gage, half the bridge has 2 gages parallel to
+ε
and
−ε
: the other half
+νε
and
−νε
:
µε
ν
=
− ⋅
+
2 10
1
6
V
GF
r
( )
Code Configuration
6 Full bridge strain gage, one half
+ε
and
−νε
, the other half
−νε
and
+ε
.:
µε
ν ν
=
− ⋅
+ − −
2 10
1 1
6
V
GF V
r
r
[( ) ( )]
Source The source variable array for the measurement(s), the input is expected as
millivolts out per volt in (the result of the full bridge instruction with a
multiplier of 1 and an offset of 0.
BrZero The variable array that holds the unstrained reading(s) in millivolts out per
volt in.
GF Gage Factor. The gage factor can be entered as a constant used for all
repetitions or a variable array can be loaded with individual gage factors
which are automatically used with each rep. To use an array enter the
parameter as arrayname(), with no element number in the parentheses.
v Poisson ratio, enter 0 if it does not apply to configuration.
StrainCalc Example
This example uses StrainCalc to find the microstrain value of a bridge output.
' Program name: STRAIN.DLD
Public Count, ZStrain, StMeas, Strain, Flag(8) ' Declare all variables as
public
'Data Table STRAINS samples every measurement when user Sets Flag(1)
High
DataTable(STRAINS,Flag(1),-1)
DataInterval(0,0,0,100) 'Interval = Scan, 100 lapses
Sample (1,Strain,Ieee4)
EndTable
'DataTable ZERO_1 stores the "zero" measurements
DataTable(ZERO_1,Count>99,100) 'Trigger on Count 100
Average(1,ZStrain,IEEE4,0)
EndTable
'Subroutine to measure Zero, Called on first pass or when user sets Flag(2)low