Model 2110 5½ Digit Multimeter Reference Manual
Section 3: Basic DMM operation
2110-901-01 Rev. C/August 2013
3-19
RTD coefficients and temperature calculation
The table below shows the default coefficient values for the PT100, D100, F100, PT385, and PT3916
RTD sensors. For the Model 2110, these values are fixed and cannot be changed. However, if you
need to use different coefficient values for these sensors, you can use the USER sensor type. The
USER sensor type allows you to enter your own values.
Sensor default coefficients
Sensor type
Alpha (
α
)
Beta (
β
)
Delta (
δ
)
R-Zero
PT100
0.003850
0.10863
1.49990
100
Ω
D100
0.003920
0.10630
1.49710
100
Ω
F100
0.003900
0.11000
1.49589
100
Ω
PT385
0.003850
0.11100
1.50700
100
Ω
PT3916
0.003916
0.11600
1.50594
100
Ω
A
B
C
NTCT
1.129241e-3
2.341077e-4
8.77546e-8
n/a
The following equations are used to calculate RTD temperature:
When t < 0
°
C:
R
t
= R
0
[1+At+Bt
2
+Ct
3
(t-100)]
When 0
°
C
≤
t < 630 °C:
R
t
= R
0
(1+At+Bt
2
)
Where:
A =
α(
1 +
δ
/100)
B = -
αδ
•
10
-4
C = -
αβ
•
10
-8
For the standard platinum RTD (SPRTD) sensor, the ITS-90 (International Temperature Scale)
standard provides two reference equations for standard platinum thermometers covering a
temperature range from 18.8033 K to 1234.93 K. However, one SPRTD usually cannot cover the
entire range, so the temperature range is divided into a few subranges.
These subranges depend on the calibration point of the temperature scale and are based on the
melting or triple points of various pure substances. For an exact list of the required elements and
details about RTD calibration, refer to NIST Technical Note 1265, “Guidelines for Realizing the
International Temperature Scale of 1990.” In each subrange, the calibration constants required for
that subrange are listed.
NTCT temperature calculation
For NTCT sensors, the temperature is calculated using the Steinhart-Hart equation:
Where R is the resistance measured by the DMM and T is the resulting temperature in Kelvin.
