Campbell Scientific 109 109-L Temperature Probe - Page 11

Model 109 Temperature Probe Maximum Steinhart-Hart Linearization Error: 0.03 °C at -50 °C Error Degrees C Steinhart & Hart - Tabulated values 0.03 0.025 0.02 0.015 0.01 0.005 0 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 -0.005 Temperature Degrees C FIGURE 6-1. Steinhart and Hart Possible Error Degrees C Worst Case Errors in 109 Temperature Measurement 0.7 Thermistor Tolerance CR200 Bridge Measurement Error (0.06% of reading+2.4 mV) 0.6 CR10X Bridge Measurement Error, CR200 Resolution (0.5 mV, 0.6 mV) 0.5 24.9 k Ohm Fixed Resistor Tolerance (0.1% + 10ppm/degC away from 25deg) 0.4 0.3 0.2 0.1 6E-16 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 -0.1 Temperature Degrees C FIGURE 6-2. Possible Errors 1The overall probe accuracy is a combination of the thermistor interchangeability specification, the accuracy of the bridge resistor, and the Steinhart-Hart equation used in CRBasic instruction Therm109() (CRBasic dataloggers). The major error component is the interchangeability specification of the thermistor. The bridge resistor has a 0.1% tolerance with a 10 ppm temperature coefficient. At temperature extremes, the possible error in the CR200(X) series measurement may be greater than the error that may exist in the probe. Probe Length: Probe Diameter: Weight with 10 ft Cable: 10.4 cm (4.1 in) 0.762 cm (0.3 in) 136 g (5 oz) 5