Series 3700A System Switch/Multimeter Reference Manual
Section 4: Basic DMM operation
3700AS-901-01 Rev. D/June 2018
4-39
Example
Calculate the temperature for a Series 44007 thermistor that measures 5
kΩ (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
RTD equations
The temperature versus resistance readings listed in the RTD reference tables are calculated using
the Callendar-Van Dusen equation. There are two equations based on different temperature ranges.
There is an equation for the
–200 °C to 0 °C range and one for the 0 °C to 630 °C range.
Equation for
–200 °C to 0 °C temperature range
R
RTD
= R
0
[1 + AT + BT
2
+ CT
3
(T
–100)]
Where:
R
RTD
= The calculated resistance of the RTD
R
0
= The known RTD resistance at 0 °C
T
= The temperature in °C
A
= Alpha [1 + (delta/100)]
B
=
–1 (alpha)(delta)(1e-4)
C
=
–1 (alpha)(beta)(1e-8)
The alpha, beta, and delta values are listed in
(on page 4-40).
