Velocity Profile Measurement of Solid Particles Using LED as a Light Source M. Marwan Mahmod, Hanis Liyana M. A., * Elmy J. Mohamad Dept. of Mechatronic & Robotic Engineering Fac. of Electrical & Electronic Engineering Universiti Tun Hussein Onn Malaysia 86400 Batu Pahat, Malaysia * elmy@uthm.edu.my Omar M. F. Marwah Dept. of Manufacturing & Industrial Engineering Fac. of Mechanical & Manufacturing Engineering Universiti Tun Hussein Onn Malaysia 86400 Batu Pahat, Malaysia mdfaizan@uthm.edu.my Abstract—Optical sensors have been widely available and used in medical applications and industries for decades. Its design comes in a wide range of varieties where each are tailored based on its type, use, size, nature of investigated materials etc. In this work, we focus on the development and investigation of an optical sensing module, which uses Light Emitting Diode (LED) as the light source and LED photosensor as detector. This sensor is to measure the velocity of a solid particle in a gas flow inside a closed pipe. Various factors such as power dissipation, wavelength of the light source, switching time and cost are considered in the design process of this sensor. The cross correlation technique is used to determine the flow rate where small particles were introduced in a natural gas flow and they went through two distanced sets of sensor module. The LED beam source in the first set of sensor will be scattered when the particle crosses it then the corresponding photodetector will collect the light signal received and generates a pulse signal. The second pulse signal is generated when the particle crosses the second set of sensor after an interval of time. The time interval measured is used to calculate the velocity of the flow. An analysis of the received pulse signals is made to determine the best configurations of the sensors. At the end of this study, we were able to develop a simple, working, and cost effective sensing module. Keywords—optical sensor; velocity measurement; particle droplet I. INTRODUCTION In various industries, it is vital to monitor the flow behavior inside closed vessels or pipes. The monitoring system can help obtaining flow information such as its rate, velocity profile and concentration profile. This information is useful in the process control where early detection of flow problem can be done and proper actions can be made in order to provide optimum flow condition. At present, there are varieties of flow monitoring tools available and widely used such as in pharmaceutical, automation and food industries. However, most of its design is application-specific where each of it differs from the other based on its type of sensor, cost, acquisition speed, nature of investigated materials etc. The fast evolution and growth of process industry have simultaneously increased the need of research and development in the process monitoring system field [1], [2]. In this project, we investigate the use of optical sensing technique to measure the velocity of a solid-gas flow. Solid materials tend to flow non-homogenously [3]. Thus, its velocity is non-uniform and varies with time. Although solid- gas flow is common in industries, there are still no successfully built solid flow measurement devices to date [4]. Most industries that involve solid-gas flow still use traditional method to monitor processes. For example, in the rice processing industry, rice grains are manually weighed before and after the rice enhancement stage to determine the production loss due to non-optimum flow condition. The weighing often stalls the production rate as it is done manually and uses human labour [5]. A real-time monitoring system would adequately improve the production rate as it provides early detection of flow problems such as flow blockage or overspeed of grains thus, adjustments could be made accordingly. Optical sensors are prominently used in various process monitoring modalities. Their fast response, simplicity and reliable performance are attractive benefits to be brought in this project. In addition, the sensors’ sensitivity is indifferent to the component distributions of investigated material, assuming all particles being measured are opaque [6]. Thus, their sensitivity is equal regardless of the sensors’ position around the pipe. Numerous researches on process imaging were done using Light Emitting Diodes (LEDs) based optical sensors, especially in developing optical tomography systems [7] – [11]. From these previous works, we learned that the image acquisition time is often inversely proportional to the image resolution quality. Hence, in this project, we investigate the use of a simpler yet moderately faster sensing module in order to obtain the particle velocity in a solid-gas flow. The cross correlation technique employed in these previous works will be adapted in this study. 978-1-4799-6428-4/14/$31.00 ©2014 IEEE