Campbell Scientific 109-L Temperature Probe - Manual (Page 15)

Model 109 Temperature Probe
7.2 Datalogger Programming
Short Cut is the best source for up-to-date datalogger programming code.
Programming code is needed when:
• Creating a program for a new datalogger installation
• Adding sensors to an existing datalogger program
If your data acquisition requirements are simple, you can probably create and
maintain a datalogger program exclusively with Short Cut. If your data
acquisition needs are more complex, the files that Short Cut creates are a great
source for programming code to start a new program or add to an existing
custom program.
Short Cut cannot edit programs after they are imported and edited
in CRBasic Editor.
A Short Cut tutorial is available in Section 4, Quickstart. If you wish to import
Short Cut code into CRBasic Editor to create or add to a customized program,
follow the procedure in Appendix A.1, Importing Short Cut Code into CRBasic
Editor. Programming basics are provided in the following section. A complete
program example can be found in Appendix B, Example Programs.
If the 109 probe is to be used with long cable lengths or in electrically noisy
environments, consider employing the measurement programming techniques
outlined in Section 8.3, Electrically Noisy Environments, and Section 8.4, Long
Cable Lengths.
Details of 109 probe measurement and linearization of the thermistor output
are provided in Section 8.2, Measurement and Output Linearization.
7.2.1 Therm109() Instruction
The Therm109() measurement instruction programs most CRBasic
dataloggers (CR6-, CR200(X)-, and CR800-series, CR1000, CR3000, and
CR5000) to measure the 109 probe. It supplies 2500 mV excitation, makes a
half-bridge resistance measurement, and converts the result to temperature
using the Steinhart-Hart equation. See Section 8.2, Measurement and Output
Linearization, for more information. Therm109() instruction and parameters
are as follows:
Therm109 (Dest, Reps, SEChan, VxChan, SettlingTime, Integ/Fnotch,
Mult, Offset)
The instruction for CR200(X) series dataloggers excludes the SettlingTime and
Integ parameters.
Variations:
• Temperature reported as °C — set Mult to 1 and Offset to 0
• Temperature reported as °F — set Mult to 1.8 and Offset to 32
• Ac mains noise filtering — set Integ/Fnotch to _60Hz or _50Hz (see
Section 8.3, Electrically Noisy Environments)
• Compensate for long cable lengths — Set SettlingTime to 20000 (see
Section 8.4, Long Cable Lengths)
NOTE
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