Thermistor Equation - Keithley 2701 User Manual

F-6 Temperature Equations
Table F-8
Type T inverse function polynomial
c =
0
c =
1
c =
2
c =
3
c =
4
c =
5
c =
6
c =
7
Error:
t = c
90
where: t

Thermistor equation

Temperature (in Kelvin) is calculated using the Steinhart-Hart equation as follows:
where: T
Table F-9
Model 2701 curve fitting constants for thermistors
Constant
Selecting a thermistor — The thermistor manufacturers specified curve fitting values (A,
B, and C) may not be exactly the same as the ones used by the Model 2701. If they are not
exactly the same, perform the following steps to select a thermistor to use with the
Model 2701:
-200°C to 0°C
(-5,603µV to 0µV)
0.0
2.594 919 2 × 10 -2
-2.131 696 7 × 10 -7
7.901 869 2 × 10 -10
4.252 777 7 × 10 -13
-16
1.330 447 3 × 10
-20
2.024 144 6 × 10
-24
1.266 817 1 × 10
0.04°C to -0.02°C
2 3
+ c E + c E + c E
0 1 2 3
is the calculated temperature in °C.
90
E is the measured voltage in microvolts.
is the calculated temperature in Kelvin.
K
lnR is the natural log of the measured resistance of the thermistor.
A, B, and C are the curve fitting constants. The constants for the three thermistor
types used by the Model 2701 are listed in
2252Ω at 25°C
(Series 44004)
A 0.0014733
B 0.0002372
C 1.074e-7
0°C to 400°C
(0µV to 20,872µV)
0.0
2.592 800 × 10
-7.602 961 × 10
4.637 791 × 10
-2.165 394 × 10
6.048 144 × 10
-7.293 422 × 10
0.03°C to -0.03°C
i
... c E
i
1
T = -----------------------------------------------------------
K
( ) [
A + BlnR + C lnR
Table
5000Ω at 25°C 10kΩ at 25°C
(Series 44007) (Series 44006)
0.001288 0.0010295
0.0002356 0.0002391
9.557e-8 1.568e-7
Model 2701 User's Manual
-2
-7
-11
-15
-20
-25
3
( ) ]
F-9.