Model 109B & 109 BAM Temperature Probe
Steinhart & Hart - Tabulated values
-0.005
0
0.005
0.01
0.015
0.02
0.025
0.03
-50
-40
-30
-20
-10
0
10
20
30
40
50
60
70
Temperature Degrees C
Error Degrees C
FIGURE 2-1. Steinhart and Hart
Worst Case Errors in 109 Temperature Measurement
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
-50
-40
-30
-20
-10
0
10
20
30
40
50
60
70
Temperature Degrees C
Po
ssib
le Erro
r Deg
rees C
Thermistor Tolerance
CR200 Bridge Measurement Error (0.06% of 2.4 mV)
CR10X Bridge Measurement Error, CR200 Resolution (0.5 mV, 0.6 mV)
24.9 k Ohm Fixed Resistor Tolerance (0.1% + 10ppm/degC away from 25deg)
FIGURE 2-2. Possible Errors
3. Installation
3.1 Soil Temperature
The 109B is suitable for burial. Whenever possible it should be placed
horizontally at the desired depth to avoid thermal conduction from the surface
to the thermistor. The recommended maximum burial depth is equivalent to 86
psi.
3
