Campbell Scientific 109 109-L Temperature Probe - Page 13

Model 109 Temperature Probe 7.2.1 CRBasic 7.2.2 Edlog 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. The Therm109() measurement instruction programs most CRBasic dataloggers (CR200(X) series, CR800 series, CR850, CR1000, CR3000, CR5000) to measure the 109 probe. It 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(Dest,Reps,SEChan,VxChan,SettlingTime,Integ,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 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) The AC Half Bridge (P5) measurement instruction programs Edlog dataloggers (CR10(X), CR510, CR500, CR23X, 21X, and CR7(X)) to measure the 109 probe in a half-bridge configuration. Polynomial (P55) applies the Steinhart-Hart equation using a fifth-order polynomial to convert the measurement to temperature (see Section 8.2, Measurement and Output Linearization, for more information): 1: AC Half Bridge (P5) 1: 1 Reps 2: 25 2500 mV 60 Hz Rejection Range 3: 1 SE Channel 4: 1 Excite all reps w/Exchan 1 5: 2500 mV Excitation 6: 1 Loc [ V_Vx ] 7: 1 Multiplier 8: 0 Offset 2: Z=1/X (P42) 1: 1 X Loc [ V_Vx ] 2: 2 Z Loc [ Vx_V ] 3: Z=X+F (P34) 1: 2 X Loc [ Vx_V ] 2: -1 F 3: 3 Z Loc [ Vx_V_1 ] 4: Z=X*F (P37) 1: 3 X Loc [ Vx_V_1 ] 2: 24900 F 3: 4 Z Loc [ Rs ] 7