Keithley 3720-ST User Manual

Section 4: Basic DMM operation Series 3700A System Switch/Multimeter Reference Manual
4-40 3700AS-901-01 Rev. D/June 2018
Equation for 0 °C to 630 °C temperature range
R
RTD
= R
0
(1 + AT + BT
2
)
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)
The alpha and delta values are listed in RTD parameters for equations (on page 4-40).
RTD parameters for equations
The RTD parameters for the Callendar-Van Dusen equations are listed below.
RTD parameters
Type
Standard
Alpha
Beta
Delta
Ω at 0 °C
PT100
D100
F100
PT385
PT3916
ITS-90
ITS-90
ITS-90
IPTS-68
IPTS-68
0.003850
0.003920
0.003900
0.003850
0.003916
0.10863
0.10630
0.11000
0.11100
0.11600
1.49990
1.49710
1.49589
1.50700
1.50594
100 Ω
100 Ω
100 Ω
100 Ω
100 Ω
Example 1
Calculate the resistance of a PT100 RTD at 100 °C (T). The following R
0
(Ω at 0 °C), alpha, and delta
values are used for the PT100 RTD (Thermistor equation (on page 4-38)):
T = 100 °C
R
0
(Ω at 0 °C) = 100 Ω
alpha = 0.003850
delta = 1.49990
Using the above alpha and delta values, A and B are calculated as follows:
A
= 0.00385 [1 + (1.4999/100)]
= 0.00385 (1.014999)
= 0.003907746
B
= –1 (0.00385)(1.4999)(1e-4)
= –1 (0.005774615)(1e-4)
= –5.774615e-7
The resistance of the RTD at 100 °C (R
100
) is then calculated as follows:
R
100
= R
0
[1 + AT + BT
2
]
= 100 {1 + [(0.003907746)(100)] + [(–5.774615e-7)(100
2
)]}
= 100 [1 + 0.3907746 + (-0.005774615)]
= 100 (1.385)
= 138.5 Ω

Keithley 3720-ST Specifications

General

Brand	Keithley
Model	3720-ST
Category	Multimeter
Language	English