Model 2750 Multimeter/Switch System User’s Manual
Temperature Equations
F-7
Selecting a thermistor
— The thermistor’s manufacturer’s specified curve fitting values
(A, B, and C) may not be exactly the same as the ones used by the Model 2750. If they are
not exactly the same, perform the following steps to select a thermistor to use with the
Model 2750:
NOTE
The specified thermistor temperature measurement accuracy of the Model 2750
(see Appendix A) is based on the curve fitting constants listed in
. If the
thermistor manufacturers curve fitting constants are not exactly the same as the
ones listed in
, accuracy will be affected.
1.
Choose the thermistor type to be used; 2252
Ω
, 5k
Ω
, or 10k
Ω
.
2.
Compare the A, B, and C constants from the thermistor manufacturer with those
used by the Model 2750 (see
).
3.
Select a thermistor that closely matches the A, B, and C constants in
.
4.
Analyze the differences between the two sets of curve fitting constants to deter-
mine the affect on measurement accuracy.
Converting K to °C
— The temperature in Kelvin can be converted to °C as follows:
T
°C
= T
K
- 273.15
where: T
°C
is the temperature in °C.
T
K
is the calculated Kelvin temperature.
Example
— Calculate the temperature for a Series 44007 thermistor that measures
5k
Ω
(R):
lnR = ln(5000) = 8.5172
A = 0.001288
B = 0.0002356
C = 9.557e-8
T
K
= 1 / {A + (BlnR) + [(C)(lnR)
3
]}
= 1 / {0. [(0.0002356)(8.5172)] + [(9.557e-8)(8.5172
3
)]}
= 1 / (0. 0. 0.000059)
= 1 / 0.003354
= 298.15
T
°C
= T
K
- 273.15
= 298.15 - 273.15
= 25°C
2750-900-01.book Page 7 Wednesday, August 3, 2011 7:56 AM
Summary of Contents for 2750
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Page 324: ...12 CommonCommands 2750 900 01 book Page 1 Wednesday August 3 2011 7 56 AM...
Page 348: ...15 SCPIReferenceTables 2750 900 01 book Page 1 Wednesday August 3 2011 7 56 AM...
Page 374: ...B Model7700ConnectionGuide 2750 900 01 book Page 1 Wednesday August 3 2011 7 56 AM...
Page 386: ...C StatusandErrorMessages 2750 900 01 book Page 1 Wednesday August 3 2011 7 56 AM...
Page 394: ...D SignalProcessing SequenceandDataFlow 2750 900 01 book Page 1 Wednesday August 3 2011 7 56 AM...
Page 408: ...E MeasurementConsiderations 2750 900 01 book Page 1 Wednesday August 3 2011 7 56 AM...
Page 428: ...G IEEE 488BusOverview 2750 900 01 book Page 1 Wednesday August 3 2011 7 56 AM...
