Keithley 2701, Руководство пользователя

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F-6 Temperature Equations Model 2701 User’s Manual
Thermistor equation
Temperature (in Kelvin) is calculated using the Steinhart-Hart equation as follows:
where: T
K
is the calculated temperature in Kelvin.
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 Table F-9.
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:
Table F-8
Type T inverse function polynomial
-200°C to 0°C
(-5,603µV to 0µV)
0°C to 400°C
(0µV to 20,872µV)
c
0
= 0.0 0.0
c
1
= 2.594 919 2
×
10
-2
2.592 800
×
10
-2
c
2
= -2.131 696 7
×
10
-7
-7.602 961
×
10
-7
c
3
= 7.901 869 2
×
10
-10
4.637 791
×
10
-11
c
4
= 4.252 777 7
×
10
-13
-2.165 394
×
10
-15
c
5
= 1.330 447 3
×
10
-16
6.048 144
×
10
-20
c
6
= 2.024 144 6
×
10
-20
-7.293 422
×
10
-25
c
7
= 1.266 817 1
×
10
-24
Error: 0.04°C to -0.02°C 0.03°C to -0.03°C
t
90
= c
0
+ c
1
E + c
2
E
2
+ c
3
E
3
... c
i
E
i
where: t
90
is the calculated temperature in °C.
E is the measured voltage in microvolts.
Table F-9
Model 2701 curve fitting constants for thermistors
Constant
2252
Ω
at 25°C
(Series 44004)
5000
Ω
at 25°C
(Series 44007)
10k
Ω
at 25°C
(Series 44006)
A 0.0014733 0.001288 0.0010295
B 0.0002372 0.0002356 0.0002391
C 1.074e-7 9.557e-8 1.568e-7
T
K
1
A BlnR
( )
C lnR
( )
3
[ ]
+ +
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2701-900-01.book Page 6 Wednesday, August 3, 2011 9:43 AM