Concept - PLCS TC
- CIMON (Unlicensed)
Analog Amount - A
Consecutively changing amounts such as voltage, current, temperature, speed, pressure and flow rate are called Analog amount. Temperature, for example, is consecutively changing by time as shown in Picture 1.1. However, because this consecutively changing amount can’t be directly inputted to PLC, thermocouple input module makes it possible to convert temperature into digital amount for PLC.
Digital Amount - D
Non-consecutively changing amount like numbers such as 0, 1, 2 and 3 is called Digital amount. The signal ON and OFF is expressed by digital amount of 0 and 1. BCD value and binary value are also Digital amount.
Compensating cable
This is a cable to compensate deviation (temperature variations) due to distance for thermocouple input module: This shows almost the same thermo-electrical characteristics in temperature of -20~90℃ for G Type and 0~150 ℃ for H Type.
Thermocouple
It is a temperature sensor consisting of 2 different metals attached and uses thermoelectric effect which makes thermoelectricity flow by generating electromotive force due to difference of temperature between both contact points. The strength of electromotive force is determined by types of attached metals and temperature for both contact points but it is not affected by shape, dimension and temperature variation of metals.
Temperature conversion characteristic
Temperature conversion to thermocouple input has non-linear characteristics.
This module converts the thermocouple input with non-linear characteristics into A/D and outputs the temperature conversion that is linearly treated.
Disconnection detection function
When Disconnection occurs between a thermocouple/parts of compensating cable and module, internal disconnection detection circuit detects short circuit by identifying larger voltage than measurement range.
RJC (Reference Junction Compensation)
Because sensors for various types of thermocouple output voltage corresponding to differences in temperature between both ends, actual temperature is measured in a way that a temperature from sensor is added to current temperature in PLC.
Currently, SP04ETO module performs reference junction compensation (RJC) using by Thermistor.