29-08-2014, 02:28 PM
OPTOELECTRONICS AND FIBER OPTIC SENSORS
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ABSTRACT
This paper presents the design and implementation of a fiber optic sensor for measurement of tilt and axial displacement. The sensing is done by intensity-modulation and reflective fiber optic displacement sensor principle. A simple referencing technique is employed here with two receiving fibers arranged on either side of a transmitting fiber. The method has been successfully employed for targets of varying reflectivities the test results on sensor performance show good agreement with theory. Analysis has been done on the repeated experimentation and results are found to be satisfactorily consistent.
The sensor measures axial and angular displacements (tilt), which are provided by appropriate micro-displacement meter and a stepper motor respectively. An axial displacement range of 2.7mm and angular displacement range of
6.30 have been obtained. This proves that the sensor is very suitable for applications in manufacturing industries especially for position and vibration control.
INTRODUCTION
Fiber optic sensor technology has matured to the extent that its impact has brought about a new trend in the present day sensing methods. The versatility of optical fiber sensors lies in the fact that they offer several advantages such as: High level of sensitivity in most of the applications. Low cost, light weight, immunity to EMI and of course, the flexibility and ruggedness most of the sensors are either intensity modulation or phase (interferometric) based, although spectral and polarization based sensors do exist.
The intensity based sensors are more popular because of their compatibility with the multimode fiber technology, ease of design and implementation, less complex hardware signed and processing. The sensitivity offered by these sensors is above the acceptable level and the extreme sensitivity achieved by the interfero-metric counter parts is not actually required in many applications
Displacement sensors with reflective intensity modulation are realized with ease and success. Tilt and axial displacement measurement and control of these parameters in a machine or the components improve the functionality to a great extent besides, improving the quality of the product. In other words position and vibration control can significantly affect industries automation in terms of yield, quality, reliability and economy of production.
Unlike the linear variable displacement transducers and accelerometers, a fiber optic displacement sensors employs a non contact method to investigate the behavior of moving part, by relating the axial displacement or tilt to a variation in the intensity of input light.
Although the axial displacement measurements based on intensity modulated fiber optic sensors have been very successfully employed for a large range of applications, their inability to
OPERATING PRINCIPLE
The basic principle of the sensor here is relating the reflected light collected by a set of fibers to the movement of surface under study. Light is emitted through a fiber to a reflecting surface and then picked up (after reflection) by a set of two fibers placed on either sides of the transmitting fiber. The monitored light intensity changes if the surface is moved axially. Also, when the surface undergoes an angular rotation (axially not displaced), the light intensity changes. The variation in the light intensity monitored at the received end is a function of the angular displacement and the axial displacement of the reflecting surfaces.
OBSERVATION AND RESULTS
First of all, a reference position is chosen before the observations and readings are taken. The mirror and the sensor head are kept parallel (flat) to each other and the axis of rotation of the mirror is aligned with the
center fiber of the sensor head .This position is called the reference position. At this position, the voltages corresponding to the two receiving fibers
FUTURE SCOPE
We conclude that the sensor setup reported here can serve as an effective measurement technique for axial and angular displacements. This is an economical and rugged way of sensing two useful parameters with single sensor head. Further the need of complex and expensive collecting optics is avoided here. Thus the sensor can find wide applications in industrial automation, robotics and process control where measurements of high accuracy is required. In this age of virtual instrumentation this kind of sensor can be easily interfaced with computer for various applications. As an extension efforts are in hand to measure both axial and angular displacement simultaneously from a single sensor head.
[attachment=67337]
ABSTRACT
This paper presents the design and implementation of a fiber optic sensor for measurement of tilt and axial displacement. The sensing is done by intensity-modulation and reflective fiber optic displacement sensor principle. A simple referencing technique is employed here with two receiving fibers arranged on either side of a transmitting fiber. The method has been successfully employed for targets of varying reflectivities the test results on sensor performance show good agreement with theory. Analysis has been done on the repeated experimentation and results are found to be satisfactorily consistent.
The sensor measures axial and angular displacements (tilt), which are provided by appropriate micro-displacement meter and a stepper motor respectively. An axial displacement range of 2.7mm and angular displacement range of
6.30 have been obtained. This proves that the sensor is very suitable for applications in manufacturing industries especially for position and vibration control.
INTRODUCTION
Fiber optic sensor technology has matured to the extent that its impact has brought about a new trend in the present day sensing methods. The versatility of optical fiber sensors lies in the fact that they offer several advantages such as: High level of sensitivity in most of the applications. Low cost, light weight, immunity to EMI and of course, the flexibility and ruggedness most of the sensors are either intensity modulation or phase (interferometric) based, although spectral and polarization based sensors do exist.
The intensity based sensors are more popular because of their compatibility with the multimode fiber technology, ease of design and implementation, less complex hardware signed and processing. The sensitivity offered by these sensors is above the acceptable level and the extreme sensitivity achieved by the interfero-metric counter parts is not actually required in many applications
Displacement sensors with reflective intensity modulation are realized with ease and success. Tilt and axial displacement measurement and control of these parameters in a machine or the components improve the functionality to a great extent besides, improving the quality of the product. In other words position and vibration control can significantly affect industries automation in terms of yield, quality, reliability and economy of production.
Unlike the linear variable displacement transducers and accelerometers, a fiber optic displacement sensors employs a non contact method to investigate the behavior of moving part, by relating the axial displacement or tilt to a variation in the intensity of input light.
Although the axial displacement measurements based on intensity modulated fiber optic sensors have been very successfully employed for a large range of applications, their inability to
OPERATING PRINCIPLE
The basic principle of the sensor here is relating the reflected light collected by a set of fibers to the movement of surface under study. Light is emitted through a fiber to a reflecting surface and then picked up (after reflection) by a set of two fibers placed on either sides of the transmitting fiber. The monitored light intensity changes if the surface is moved axially. Also, when the surface undergoes an angular rotation (axially not displaced), the light intensity changes. The variation in the light intensity monitored at the received end is a function of the angular displacement and the axial displacement of the reflecting surfaces.
OBSERVATION AND RESULTS
First of all, a reference position is chosen before the observations and readings are taken. The mirror and the sensor head are kept parallel (flat) to each other and the axis of rotation of the mirror is aligned with the
center fiber of the sensor head .This position is called the reference position. At this position, the voltages corresponding to the two receiving fibers
FUTURE SCOPE
We conclude that the sensor setup reported here can serve as an effective measurement technique for axial and angular displacements. This is an economical and rugged way of sensing two useful parameters with single sensor head. Further the need of complex and expensive collecting optics is avoided here. Thus the sensor can find wide applications in industrial automation, robotics and process control where measurements of high accuracy is required. In this age of virtual instrumentation this kind of sensor can be easily interfaced with computer for various applications. As an extension efforts are in hand to measure both axial and angular displacement simultaneously from a single sensor head.