©
National Instruments Corporation
5
TBX-68S Isothermal Terminal Block
Rack-Mounting the TBX-68S
When you have completed signal connections and terminal block
installation, you can mount the TBX-68S assembly into your rack. If you
are using the National Instruments TBX Rack-Mount Assembly, refer to
the
TBX Rack-Mount Installation Guide
for instructions.
If you are not using this rack-mount assembly, mount the TBX-68S directly
by snapping its base onto the DIN rail with a firm push.
To remove the TBX-68S from the DIN rail, place a flathead screwdriver
into the slot above the terminal block base and pry it away from the rail.
Cold-Junction Temperature Sensor
The TBX-68S temperature sensor voltage output varies from 198.54 mV to
19.58 mV over the temperature range 0° to 55° C, respectively, and has an
accuracy of ±0.5° C over the 15° to 35° C temperature range and ±0.9° C
over the 0° to 15° and 35° to 55° C temperature ranges.
1
You can use the following formulas to convert the cold-junction sensor
voltage to cold-junction temperature:
T(° C) = T
K
– 273.15
where T
K
is the temperature in kelvin
a = 1.295361 x 10
-3
b = 2.343159 x 10
-4
c = 1.018703 x 10
-7
R
T
= resistance of the thermistor
V
TEMPOUT
= output voltage of the temperature sensor
1
Includes the combined effects of the temperature sensor accuracy and temperature difference between the temperature sensor
and any screw terminal. The temperature sensor accuracy includes tolerances in all component values, the effects caused by
temperature and loading, and self-heating.
T
K
1
a
b
R
T
ln
(
)
c
R
T
ln
(
)
3
+
+
[
]
---------------------------------------------------------------
=
R
T
189
K
V
TEMPOUT
2.5
V
TEMPOUT
–
----------------------------------
⎝
⎠
⎛
⎞
=
T
°
F
( )
[T(
°
C
) ]
9
5
------------------------
32
+
=
