ADD LADDER TO READING THE D MEMORY : D5004 OF PLC
Next , make a ladder to monitor the movement of the numbers at address D5004.
We are to scale according to the signal coming from the input current of 4-20mA.
Back to the program, then enter a program in the ladder in the PLC.
Do Offline your computer with PLC.
Fig 51 Insert new ladder
The ladder will be named New Program 1.
Click on Section 1.
Create a ladder like the example below:
Note: FirstWordRe… is D5004 address.
Do online back with the PLC . PLC> Work Online> Online dengan PLC via USVB? > Yes.
Transfer your ladder with : PLC> Transfer> To PLC> OK>…Continue?>Yes
Program Mode?> Yes> OK> Monitor Mode?> yes
Your program will compiled to PLC.
Change the number inside its addresses:
- D1010 since 0 change to 100 ( its will be as realtime reading scaled number )
- D1002 since 0 change to 1250
- D1004 since 0 change to 288
- Note: The value inside the D1014 and D1016 must be shown as 0 value.
Then increase and apply the input to 20mA. Pay attention that address D1014 & D1016. Its must be 100.
CUSTOMIZED FROM SCALING TO PRESSURE
What if the 4-20mA current source becaming a pressure sensor source that operating between 0 and 350 bar? Can we set our TM4 to displaying this number? The answer is: YES.
We simply change the number at the SCALE address ( D1010 ) which was originally 1000 to 350. Of course the numbers that come out in the ladder calculation will follow the sensor.
Example: When the sensor reads a pipe pressure of 150 bar, the sensor will send a signal of 10.86mA of 4-20mA.
Of course TM4 will assume that there is a thermocouple temperature of 688 degrees and becomes 145 bar after scaling.
There is a difference of 3%, but this can still be used for non-vital monitoring applications.
MAKING COMPENSATION CALCULATOR
See that the average difference is 3.5% and it needs to be compensated is from 5% signal input up to 80%.
We can do this by creating a compensation ladder like the example below:
RESULT OF AFTER CALCULATION TABLE
Furthermore, the results after the compensation ladder will be as follows:
MENAMBAH PARAMETER LAINNYA
Could we add some parameter value in TM4 modul for scaling out like this sample ladder?
The answer is: YES. You can.
You just only connect the modified 4-20mA signal by the simple converter then we’ll registers to D5010 and so on also make additional ladder like the example above.
x
WIRING
X
REGISTERING THE MODBUS ADDRESS INSIDE THE PLC D 5XXX MEMORY
X
MAKE THE SCALING
X
MAKING MONITORING SYSTEM
If the result of scaling number has entered to the PLC then of course it will be easy for us to make monitoring. As for making monitoring we can do with a variety of applications.