PLC Program to Display Level of a Tank


This is a PLC Program to Display Level of a Tank.

Problem Description

There is a tank of which level is controlled automatically. Display level of this tank continuously. Perform this in PLC using Ladder Diagram programming language.

Problem Solution
  • Continuous measurement is necessary in this case.
  • Continuous level measuring devices such as Ultrasonic, Radar, Capacitive or Pressure gauge level sensor can be used.
  • Output of these sensors are in analog form, so to deal with such analog data, analog modules are used in PLC.
  • Analog modules convert analog signal into equivalent hex form.
  • Convert this into level height in Meter or in any other parameter to display on the screen.
PLC Program

Here is PLC program to Display Level of a Tank, along with program explanation and run time test cases.

List of Inputs and Outputs
 I:1	= Input from transmitter	(Input)
 N7:0	= Register to store input data	(Register)
 N7:1	= Register data to be displayed	(Register)
 O:6	= Display address		(Output)
 TOD	= Decimal into BCD conversion	(Compute)

Ladder diagram to display level of tankplc-program-display-level-tank-01

Program Description
  • There is no any input is given to start the process since we want continuous displaying of tank level.
  • When level in tank rises, output of sensor increases accordingly.
  • Suppose we have a tank with height 1000cm which is 10m.
  • Converting 16bit data into 1000cm height, 65 is the answer which means, increment of 65 is obtained per centimeter rise in tank level.
  • Input data from I:1 is continuously moved to N7:0 which means data in N7:0 register continuously varies.
  • Value stored in N7:0 is divided by 65 and stored in N7:1 register to display tank level in Centimeters.
  • Value stored in N7:1 register is first converted into equivalent BCD number before feeding it to display which is connected with output module at address O:6.
  • Accuracy of this method for 1000cm is ±0.8%.
Runtime Test Cases
Input	        Output                  	Physical Elements
I:1 = 65536	N7:0 = FFFFh                	Store input to register
I:1 = 65536	N7:1 = 03F0h, O:6 = 1008(In cm)	Displays 1008cm on the screen
I:1 = 32768	N7:1 = 01F8h, O:6 = 504(In cm)	Displays 504cm on the screen

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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