Abstract—Process industries require several thousand control points for smooth operation, for which different sensors are installed at various points distributed across the plant. At present the sensors include Temperature Detector (RTDs), Thermo couple (TC) for temperature measurement, strain Gauge (SG) for pressure measurement, cylindrical capacitive transducer for moisture measurement etc., other parameters of measurement include flow, quality of oil, position of object etc. For all those measurements different type of sensors are required. From these sensors analog signals are generated and then brought to the operator station. Then these signals are converted to digital signal for feeding to computer. The computer converts the digital signals to engineering units like Degree Centigrade, parts per million (PPM), etc, using the look up table value stored inside the computer, by linear interpolation method. These values are then compared with normal values stored inside computer and reported for abnormalities. The system generates control signal afterwards. This type of control signal generation is tedious procedure with the following disadvantages. Different sensors are required for different parameter measurement. Also analog signals give errors during long distance transmission. Again analog to digital conversion is required. To overcome all these difficulties, the state of art technology Digital Image Processing (DIP) is experimented for replacing different types of sensors. Only web (Digital) cameras are installed at various parameter measuring points. Let us consider a case of level measurement. A digital camera installed near the boiler drum in a Thermal power station takes continuous photographs of water levels and forwards the digital image signal to the computer at regular interval. These images are compared with standard image stored inside the computer with suitable algorithm. When the received image matches the standard image, control action is initiated. The same procedure can be adopted with digital camera for moisture measurement, oil density measurement, flow measurement, etc. This system gives real time display of various field images super imposing on the animated mimic diagrams in computer monitor, which is not possible in the old environment with analog sensors. MATLAB is extensively used. JPEG image file format is used.

Index Terms—Sensors, DIP, MATLAB, JPEG

A. Justin Diraviam is with Sardar Raja College of Engineering, Tirunelveli
S. P. Victor is with St.Xavier’s College (Autonomous), Palayamkottai.
G. Rajakumar is with Francis Xavier Engineering College, Tirunelveli.
K. Rajappan is with Sri Subramanya College of Engineering and Technology, Palani.
D. Manimegalai is with National Engineering College, Kovilpatti.

Cite: A.Justin Diraviam, Dr.S..P.Victor, G.Rajakumar, Dr. K. Rajappan and Dr.D.manimegalai, "Replacing Various Analog Signal Sensors with Digital Cameras," International Journal of Computer and Electrical Engineering vol. 3, no. 1, pp. 84-93, 2011.