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Model 109SS Temperature Probe
1: Excite-Delay (SE) (P4)
1: 1 Reps
2: 25 2500 mV 60 Hz Rejection Range (Delay must be zero)
3: 1 SE Channel
4: 1 Excite all reps w/Exchan 1
5: 2 Delay (0.01 sec units)
6: 2500 mV Excitation
7: 3 Loc [V_Vx ]
8: .0004 Multiplier
9: 0.0 Offset
6. Measurement Details
Understanding the details in this section are not necessary for general
operation of the 109SS Probe with CSI's dataloggers.
The Therm109 Instruction outputs a 2500 mV excitation and measures the
voltage across the 24.9 K resistor (Figure 6-1). The thermistor resistance
changes with temperature.
EX
HI
AG
G
BLACK
RED
PURPLE
CLEAR
24.9K
Ω
, 0.1%
10K3AI
THERMISTOR
FIGURE 6-1. 109SS Thermistor Probe Schematic
The measured voltage, V, is:
t
EX
R
VV
+
=
900,24
900,24
Where V
EX
is the excitation voltage, 24,900 ohms is the resistance of the fixed
resistor and R
t
is the resistance of the thermistor
10