Experiment No. 3(level Controller)High-sensitivity temperature-independent differential

pressure sensor using fiber Bragg gratings

Abstract: By means of novel packaged-structure design, a temperature independent differential pressure sensor based on fiber Bragg gratings with high sensitivity is experimentally demonstrated. The differential pressure sensitivity of the sensor can reach to 821.87nm/MPa. This device can also be used for simultaneous measurement of temperature and differential pressure, which is suitable for applications involving measurement of liquid level, liquid density or specific gravity detection.

IntroductionRecently the sensitivity of fiber Bragg grating pressure sensors are greatly enhanced by using several different design methods . For further extending their applications, fiber grating pressure sensors are also applied in liquid level or water-depth measurement Differential pressure (DP) measuring mechanisms for high pressure and liquid-flowing-rate detection are also applied in fiber Bragg grating pressure sensors. For air pressure and temperature control of cabin in airplane, submarine and laboratory or for production room in a pharmaceutical and electronic factory, the measurement sensitivity of differential pressure and temperature sensing device is important factor for providing a comfortable and safe working place. In this paper, a new designed differential pressure fiber sensor based on FBGs has been demonstrated, and in which two identical FBGs are packaged in a temperature compensated metal structure. In this paper, the differential pressure sensor based on fiber Bragg gratings is firstly experimentally demonstrated to have the maximum sensitivity of 821.87nm/MPa for our knowledge. Therefore, by means of this simple packaging construction, high-sensitivity temperature-independent differential pressure sensor can be achieved with a nice linearity for applying in the measurement of liquid level, liquid density or specific gravity detection.

PrincipleThe sensor has a metal cage composed of two metal cylinders, in which a diaphragm consists of a silicone rubber sandwiched between two metal plates located in the middle of sensor structure. Thus, this sensor includes two symmetrical pressure cavities separated by the diaphragm as shown in Fig

The schematic (a) outer and (b) inner structure of differential pressure sensor.ConclusionA simple, temperature-independent and novel grating-packaged differential pressure sensor is experimentally demonstrated with the maximum sensitivity of 821.78 nm/Mpa. Its operation mechanism is based on one of two fiber Bragg gratings to be compressed and the other to be extended by a diaphragm. This sensor has a potential application in a simultaneous differential pressure and temperature control system and is expected to be used in liquid density or specific gravity measurement system.

Reference: Received 15 Aug 2008; revised 16 Sep 2008; accepted 20 Sep 2008; published 24 Sep 2008

29 September 2008 / Vol. 16, No. 20 / OPTICS EXPRESS 16018