Fiber Optic Pressure Sensor structure, working, advantages, disadvantages
This page describes structure, working operation, advantages and disadvantages of Fiber Optic Pressure Sensor. It mentions Fiber Optic Pressure Sensor advantages or benefits and Fiber Optic Pressure Sensor disadvantages or drawbacks.
Fiber Optic Pressure Sensor structure | Fiber Optic Pressure Sensor working operation
The fiber optic pressure sensors are categorized into non-interferometric and interferometric types. The figure-1 depicts simple structure of fiber optic pressure sensor of non-interferometric type. As shown, it consists of three components viz. Sensing head with metal diaphragm, cable (with two multi-mode fibers) and optoelectronic systems (with LED/Photodetectors etc).
Light from LED source is allowed to be transmitted through one fiber and the reflection from metal diaphragm is taken through the second fiber. This reflected signal is received by the detector and other signal conditioning circuit. Diaphragm displacement depends on extent of applied pressure. This modulates intensity of detector's signal. The sensor is also known as intensity modulated pressure sensor.
The response of fiber optic pressure sensor depends on following parameters.
• Shape, diamter and thickness of diaphragm
• Core and cladding diameter of fiber
• Numerical aperture (NA)
• distance between two fibers
• Fiber to diaphragm distance at zero pressure
Benefits or advantages of Fiber Optic Pressure Sensor
Following are the benefits or advantages of Fiber Optic Pressure Sensor:
➨It offers unique benefits of measuring pressure in harsh environment with temperature as high as 300 oC and pressure of about 300 bar.
➨It can withstand against high level of EM (Electromagnetic) interference and presence of explosive or corrosive media. It is immune against noise, crosstalk and ground loop. It eliminates spark and shock hazards. These are optical isolation benefits of fiber optic pressure sensor.
➨It is simple in construction and does not require optical components e.g. single mode fiber, optical modulator, beam splitters etc.
➨It is relatively lower in cost.
➨It is small in size and mass.
➨It offers low signal attenuation for remote measurements.
➨The sensor is designed to function reliably over billions of pressure cycles.
➨It offers performance characteristics such as high resolution, high dynamic range, good linearity, low temperature sensitivity, multiplexing capability etc.
Drawbacks or disadvantages of Fiber Optic Pressure Sensor
Following are the drawbacks or disadvantages of Fiber Optic Pressure Sensor:
➨The sensing element and fiber optic cable are fragile.
➨It is poorly compatible with process environments.
➨Radiation induces darkening of the fiber optic cable. This results into increase in attenuation.
➨Complex and expensive signal processing equipments are required.
➨Static pressure measurements deliver poor performance.
➨Intensity modulated type of pressure sensors are vulnerable to fluctuations in the transmission characteristics of the fiber optic cables. This is due to environmental and mechanical stressors, detector sensitivity, efficiency of light sources with respect to aging and temperature.
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