RUNG000 is a latching rung to operate the system through Master Start and Stop PB.
RUNG001 comprises all the conversion needed to control level of the tank.
Output of transmitter is in current signals which is 4-20mA.
When output is 4mA, Analog Input Module converts it into 16bit equivalent hex numbers. Hence when input
to Analog module is 4mA, it stores 0000h into register and when 20mA, it stores FFFFh into register. Here
register N7:0.
Let’s say here height of the tank is 4m or 400cm. By converting it into equivalent hex, change in value per
centimeter is 164.
Value of N7:0 is then multiplied with 173 because when Level reaches 380cm, output is 62259 in decimal.
So when output at 380cm is multiplied with 173, we get full FFFFh at N7:2 to operate valve to fully close.
This multiplication is stored into N7:2 register. Digital to Analog conversion of value stored in N7:2 is
performed inside the processor and equivalent mA current is received from terminal O:3.
Current to Pneumatic converter then converts current signals into equivalent 3-15psi pneumatic signal and
adjusts valve opening.
Runtime Test Cases
Input
Output Valve percentage open
N7:0 = 0000h
O:3 = 0000h
Valve fully open
N7:0 = F333h
O:3 = FFFFh
Valve fully closed
N7:0 = 7999h
O:3 = 7FFFh
Valve 50% open
PLC Program for Heating and Mixing of Products
This is a PLC Program for Heating and Mixing of Products.
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