Campbell Scientific CR800 and CR850 Measurement and Control Systems - Manual (Page 297)

Section 8. Operation
297
Table 63. StrainCalc() Instruction Equations
StrainCalc()
BrConfig Code Configuration
6
Full-bridge strain gage. Half the bridge has two gages parallel to + and
-
, and the other half to - and + :
where:
• : Poisson's Ratio (0 if not applicable)
• GF: Gage Factor
• V
r
: 0.001 (Source-Zero) if BRConfig code is positive (+)
• V
r
: -0.001 (Source-Zero) if BRConfig code is negative (-)
and where:
• "source": the result of the full-Wheatstone-bridge measurement (X = 1000 *
V
1
/ V
x
) when multiplier = 1 and offset = 0.
• "zero": gage offset to establish an arbitrary zero (see FieldCalStrain() in
FieldCal() Demonstration Programs
(p. 154)
).
StrainCalc Example: See FieldCalStrain() Demonstration Program
(p. 162)
8.1.4 Thermocouple
Thermocouples are easy to use with the CR800. They are also inexpensive.
However, even though the Quickstart Tutorial
(p. 33)
uses a thermocouple as an
exercise in measurement, the CR800 is not designed for accurate thermocouple
measurements when thermocouples are attached directly to the CR800 wiring
panel. The lack of an insulating wiring terminal cover and the nature of the
plastic encasement will probably induce significant error in the reference junction
temperature measurement. If an external reference junction is to be used,
Campbell Scientific strongly encourages users to carefully evaluate relevant
parts of the Thermocouple Measurements section of the CR1000 Datalogger
Operator's Manual, which is available at www.campbellsci.com.
8.1.5 Pulse
Figure Pulse-Sensor Output Signal Types
(p. 39)
illustrates pulse input types
measured by the CR800. Figure Switch-Closure Pulse Sensor
(p. 298)
is a
generalized schematic showing connection of a pulse sensor to the CR800. The
CR800 features two dedicated pulse-input channels, P1 through P2, and four
digital I/O channels, C1 through C4, for measuring frequency or pulse output
sensors.
As shown in table Pulse-Input Channels and Measurements
(p. 39),
all CR800
pulse-input channels can be measured with CRBasic instruction PulseCount().
PulseCount() has various parameters to customize it to specific applications.
Digital I/O ports C1 through C4 can also be measured with the TimerIO()