Eaton ELCM Series, Руководство по эксплуатации

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E L C O p e r a t i o n M a n u a l
F o r m o r e i nf o r m a t i o n v i sit :
w w w. e a t o n . c o m
MN05003006E 1-60
3.1.5 ELC-TC04ANNN
3.1.5.1 The Thermocouple Temperature Sensor
A thermocouple is composed of conductors of two different materials. When a temperature
difference occurs at the two ends of the thermocouple, the thermocouple will generate a voltage
signal in proportional to the temperature difference. The voltage signal ranges from tens of uV to
thousands of uV; therefore, we need to magnify the voltage when using it.
The thermocouple temperature sensor indicates temperature by differential voltage, and this
eliminated eliminates external interferences the two pairs of data are a differential operation.
Therefore, it is much more stable than a thermistor, resistive thermometer or thermal resistor and
is widely applied in the industry.
The thermocouple is a loop constructed by two different metallic wires welded or twisted together
(see the figure below). Different metals make two junctions in the loop. One junction is called
“measuring junction” or “hot junction”, and the other is “reference junction” or “cold junction”.
Placing the two junctions in different temperatures will cause a loop voltage (i.e. Seebeck Effect),
and the loop voltage is in proportional to the temperature difference between the two junctions.
The loop voltage and the two junctions equate equation:
( )
∫
− =
2
1
T
T
B A
dT Q Q V
(A)
In which Q = the heat conduction coefficient of the metal
How a thermocouple works
The heat conduction coefficient of QA and QB have nothing to do with the temperature.
Therefore, equation (A) can be simplified into equation (B), a more frequently used equation:
V = α (T
2
-T
1
)
(B)
There are two types of thermocouple thermocouples, wrapped thermocouple thermocouples and
bare thermocouples. The wrapped thermocouple is wrapped with a layer of metal as protection.
The wrapped thermocouple is used for measuring temperature of a liquid and the bare
thermocouple is for measuring gas temperatures. Different thermocouples sense different
temperature ranges and have different output signals, . The maximum temperature varies with
different materials and wires of different diameters.
3.1.5.2 Introduction
The ELC-TC04ANNN allows the connection of four thermocouple sensors (Type J.K.R.S.T).
There are 49 Controlled Registers in each module (each register is 16 bits). This module
(ELC-TC04ANNN) can read/write configuration and operational data via the FROM / TO