©
National Instruments Corporation
11
NI TB-2627 Installation Instructions
5. Use the Cold-Junction Sensor Output
A cold-junction sensor (thermistor) is located near the J13 connector on the
PCB of the NI TB-2627. The cold-junction sensor outputs 0.2 V to 0.024 V
from 0 °C to 50 °C. From 15 °C to 35 °C, the NI TB-2627 has an accuracy
of ±0.5 °C. From 0 °C to 15 °C and 35 °C to 50 °C, the NI TB-2627 has an
accuracy of ±1.0 °C.
NI software can convert a thermistor voltage to the thermistor temperature
for the circuit diagram used in the NI TB-2627 and shown in Figure 6.
Figure 6.
Temperature Sensor Circuit Diagram
For example code, visit
ni.com/zone
, click the Example Code link in the
navigation bar, and enter
PXI-2527
in the Search field. Alternatively, you
can use the following formulas.
T
(°C) =
T
K
– 273.15
where
T
K
is the temperature in Kelvin,
where
a
= 1.295361
×
10
–3
,
b
= 2.343159
×
10
–4
,
c
= 1.018703
×
10
–7
, and
R
T
= resistance of the thermistor in ohms,
4.7 k
Ω
1%
189 k
Ω
0.1%
CJTEMP
1
2
1
2
2
+
5 k
Ω
at 25
o
C
10 µF
16 V
0.1 µF
0.1 µF
–t
o
+5 V
2.5 V
LM 4040
2.5 V
0.1%
T
K
1
a b
R
T
ln
(
)
c
R
T
ln
(
)
3
+
+
[
]
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