Campbell CR6 Series, Operator'S Manual

Page: 296 / 690

Section 7. Installation
296
Scan (10,Sec,1,0)
'CS100 Barometric Pressure Sensor measurement BP_mmHg
PortSet (3,1)
Delay (0,2,Sec)
VoltSE (BaroPressure1,1,mV5000,5,1,0,15000,0.2,600)
PortSet (3,0)
'VW Piezometer measurement : Temperature and Pressure
AVW200(AVWRC,ComC1,0,200,VW(1,1),1,1,1,1000,4000,1,_60Hz,1,0)
'Calculate digits and degrees C from the VW measurements
Digits1 = (VW(1,1)^2)/1000
Temperature1 = 1/(1.4051E-3 + 2.369E-4 * LN(VW(1,6)) + 1.019E-7 _
* LN(VW(1,6))^3)-273.15
'==Field zero points calibration for sensor==
'FieldCal(Function,MeasureVar,Reps,0,OffsetVar,ModeVar,0,Index,Avg)
FieldCal (4,Equation_Parameters(),3,0,ZeroFactor(),ModeZero1,0,1,1)
'Calculate Pore Pressure (PSI) using Digits, Temperature and calibration constants
Pressure1 = (GF1 * (Digit_ZeroPoint - Digits1) + Temperature1_K * _
(Temperature1 - Temperature_ZeroPoint) _
- (BaroPressure1 - Baro_Zero)*0.014503)
CallTable CalFact
CallTable Table1
NextScan
EndProg
7.7.12.6 Field Calibration Strain Examples
Related Topics:
• Strain Measurements — Overview
(p. 78)
•
Strain Measurements — Details
(p. 413)
•
FieldCalStrain() Examples
(p. 296)
Strain-gage systems consist of one or more strain gages, a resistive bridge in
which the gage resides, and a measurement device such as the CR6 datalogger.
The FieldCalStrain() instruction facilitates shunt calibration of strain-gage
systems and is designed exclusively for strain applications wherein microstrain is
the unit of measure. The FieldCal() instruction (see Field Calibration Examples
(p. 283))
is typically used in non-microstrain applications.
Shunt calibration of strain-gage systems is common practice. However, the
technique provides many opportunities for misapplication and misinterpretation.
This section is not intended to be a primer on shunt-calibration theory, but only to
introduce use of the technique with the CR6 datalogger. Campbell Scientific
strongly urges users to study shunt-calibration theory from other sources. A
thorough treatment of strain gages and shunt-calibration theory is available from
Vishay using search terms such as 'micro-measurements', 'stress analysis', 'strain
gages', 'calculator list', at:
http://www.vishaypg.com