Campbell Scientific CR3000 Micrologger - Manual (Page 168)

Section 7. Installation
168
4. The zero function of FieldCalStrain() allows the user to set a particular strain
as an arbitrary zero, if desired. Zeroing is normally done after the shunt
calibration.
Zero and shunt options can be combined through a single CR3000 program.
The following program is provided to demonstrate use of FieldCalStrain()
features. If a strain gage configured as shown in figure Quarter-Bridge Strain-
Gage Schematic
(p. 168)
is not available, strain signals can be simulated by building
the simple circuit, substituting a 1000-Ω potentiometer for the strain gage. To
reset calibration tests, use the support software File Control
(p. 456)
menu to delete
.cal files, and then send the demonstration program again to the CR3000.
Case: A 1000-Ω strain gage is placed into a resistive bridge at position R1. The
resulting circuit is a quarter-bridge strain gage with alternate shunt-resistor (Rc)
positions shown. Gage specifications indicate that the gage factor is 2.0 and that
with a 249-kΩ shunt, measurement should be about 2000 microstrain.
Send CRBasic example FieldCalStrain() Calibration Demo
(p. 169)
as a program to
a CR3000 datalogger.
Figure 51: Quarter-bridge strain-gage schematic with RC-resistor shunt