Campbell Scientific CR3000 CR3000 Micrologger - Page 306

Section 8. Operation Table 66. StrainCalc() Instruction Equations StrainCalc() BrConfig Code Configuration Half-bridge strain gage. One gage parallel to + , the other parallel to : 3 Full-bridge strain gage. Two gages parallel to + , the other two parallel to - : 4 Full-bridge strain gage. Half the bridge has two gages parallel to + and - , and the other half to + and - : 5 Full-bridge strain gage. Half the bridge has two gages parallel to + and - , and the other half to - and + : 6 where: • : Poisson's Ratio (0 if not applicable) • GF: Gage Factor • Vr: 0.001 (Source-Zero) if BRConfig code is positive (+) • Vr: -0.001 (Source-Zero) if BRConfig code is negative (-) and where: • "source": the result of the full-Wheatstone-bridge measurement (X = 1000 * V1 / Vx) when multiplier = 1 and offset = 0. • "zero": gage offset to establish an arbitrary zero (see FieldCalStrain() in FieldCal() Demonstration Programs (p. 158) ). StrainCalc Example: See FieldCalStrain() Demonstration Program (p. 167) 8.1.4 Thermocouple Note Thermocouples are easy to use with the CR3000. They are also inexpensive. However, they pose several challenges to the acquisition of accurate temperature data, particularly when using external reference junctions. Campbell 306