Design of a Hall Probe Pressure Transmitter Using Bellows

convention of a dorm study crush Transmitter use shout as Sensor R. Sarkar, Animesh Ghosh, Lipika Ghosh and N. Mandal Asansol Engineering College Vivekananda Sarani, Kanyapur, Asansol-713305 E-mail email& one hundred sextettetyprotected com, ghoshanimesh. email&160protected com, email&160protected com Abstract Bel offsetlys, an elastic type drag signal detection element is generally apply as a local indicator. To transmit the signal of shout to a remote distance some technique is needed.In the limn paper a Hall study detector has been used to convert the bellow doing into potential drop signal which can be converted into 4 20 mA current signal and transmitted to a remote indicator. It has been notice that the transducer and vector returns against drive nominate a very good one-dimensionality and repeatability. The necessary theoretical equalitys along with experimental results are inform in the paper. Keywords crush measurement, bellows, Pressure vecto r, Magnet, Hall Probe. I. INTRODUCTION Pressure is an important quantity and controlling technical parameter during industrial production process.In order to curb industrial production well, draw should be accurately measurable and controlled. Pressure can be measured in scathe of absolute or count on. The absolute nip can be measured in terms of height of a liquid column in a manometer whereas the bore pressure is measured by different types of sensing elements 1-4. As for example radio-controlled aircraft tube, diaphragm, capsule, bellow element etc. operate as primary perception elements for measuring positive or negative green goddess pressure. The sensors like argument gauge, piezoresistance, LVDT, capacitive element, inductive element etc. ct as standby sensors to measure positive or negative gauge pressure. The negative gauge pressure or vacuum pressure can likewise be measured by many other sensors like pirani gauge, ionization gauge, McLeod gauge etc. In indu strial application it is required to transmit the measured pressure to a remote distance. Hence in a pressure transmitter, the change of sensor parameter due to the change of fluid pressure is converted into an electric or pneumatic signal by use a suitable transducer and that signal after amplification is transmitted to a remote receiver.Thus the pressure transducer is a vital part of any pressure transmitter and its performance determines the reliability of operation of the transmitter. Many schools on development of reliable pressure transducer are still being reported by different groups of workers. B. Raveendran et al. 5 have patterned and developed a MEMS base piano tuner modular pressure transmitter. A Bourdon tube base pressure transmitter unit using an improved inductance twain network has been studied by S. C. Bera et al. 6. Y. Ruan et al. 7 have developed a mul stopoint receiving set pressure transmitting system composed of pressure sensor PTB203, A/D convertor A DC0804, MCU STC89C52, wireless communication faculty CC1101, receiver module STC89C52, CC1101 and display module LCD1602. Zeng Mingru et al. 8 have developed a HART communications protocol base well-grounded pressure transmitter which is compatible with both line of latitude and digital signals. K. Subramanian et al. 9 have developed MEMS type capacitive pressure sensor with sensitivity of the order of few fF/ kPa. Universal frequency to digital converter (UDFC) technique has been used by S.Y. Yurish 10 to develop an intelligent digital pressure transducer. A multiplexed frequency transmitter technique has been used by R. Vrba et al. 11 to figure of speech a reliable pressure transducer using ceramic diaphragm. In the present paper, a sign try out found pressure measurement technique has been developed. In this technique a permanent draw is placed on the tip of the bellows with the Hall probe sensor on the outgo of the outside fitting of bellows chamber as shown in Fig. 1 . The causal agent of the bellows tip is measured by a anteroom probe sensor.With the change of pressure the distance amidst magnet and the mansion houseway sensor decreases and so the magnetic intensity at the sensor increases. The Hall sensor senses this increase of magnetic field intensity and accordingly its sidetrack electromotive force increases with the increase of pressure. This signal is non additively related with the movement of float. But for very slender movement of the bellows this finage will be almost linear. The experimental results are reported in the paper. The block diagram of the proposed transducer is shown in Fig. 1. necessary athematical equations have been derived to explain the theory of operation of the transducer as well as transmitter. A prototype unit along with the signal conditioner has been designed and fabricated. The experiments have been performed to find out the static feature articles of the sensor, transducer and transmitter. The ex perimental results are reported in the paper. A very good linearity and repeatability of results with adjustable sensitivity of the transducer has been ascertained. pic Fig. 1 Diagram of the proposed transducer along with float and hall probe sensorII. METHOD OF arise In the present paper the pressure is sensed by a bellows. A magnet is placed on the top of the bellows. And the hall probe on the bellows chamber. The float movement of the bellows is converted into potency by a hall probe sensor. Output potential is amplified by an instrumentation amplifier INA101 and then converted into 4-20 mA current signal using signal conditioning circuit. This signal is then transmitted to remote spot with negligible loss. Let the pressure is pic and the corresponding height of the bellows tip from reference is pic.In bellows the height of the tip is proportional to pressure and is pen as pic(1) where pic is the unvaried Now the distance of the hall probe from the magnet is pic(2) where pic is the total length of the hall probe from reference. In the present work the magnet is selected to be a circular permanent magnet. Let the radius and comprehensiveness of the magnet be pic andpic respectively. Hence magnetic field at the hall probe due to magnet is pic(3) where pic is the constant depending on the perch strength of the magnet, its radius and permeability of air which are all constants.Since pic equation (3) is reduced to pic (4) pic(5) The above equation is equally true for very low pressure also. Since at low pressure pic, so equation (5) is reduced to pic (6) Now the output hall voltage pic of the hall sensor is proportional to pic if the current passing through the sensor be kept constant and hence it is given by pic(7) where pic is the constant of proportionality. Hence from equations (5) &038 (7) pic (8) or, pic(9) where pic is another constant. accordingly from equations (1), (8) and (9), the output from hall probe is given by pic(10) pic (11) pic(12) The refore output is linearly related with pressure. III. DESIGN In the present design a cylindrical permanent magnet is selected of inner radius pic, depth pic, width pic. In our present design, pic. The output of hall sensor is amplified by INA101 based instrumentation amplifier. The gain of the instrumentation amplifier is set by external impedance R1. This output signal is outset converted into amplified voltage signal picin the scope 1-5 volt D. C. and then into current signalpic in the range 4-20mA D. C. y a signal conditioner circuit as shown in Fig. 2. After calibration the output of the transmitter becomes 4mA when picis 1 volt and pressurepicis zero psig and 20mA when picis 5 volt and pressurepicis at maximum range picof the bellows. Hence the transmitter voltage outputpic in volt and current outputpicin mA may be written as, pic (13) and pic (14) From (13) and (14), pic (15) where picand pic(16) pic Fig. 2. Block diagram of the proposed pressure transmitter using bellows e lement as sensing twist pic Fig. 3 Circuit diagram of hall probe based pressure indicator IV. EXPERIMENT The experiment is performed in two steps. In the first step, the proposed transducer was designed, fabricated and mounted on the outside cover of bellows chamber as shown in Fig. 1. The bellows with the above sensor was first fitted with a deathly weight tester and the dead weight of the dead weight tester was increased in steps and in individually step the Hall voltage output is measured and the characteristics of the hall sensor based transducer unit is determined.The characteristic graph obtained by plotting Hall voltage against Pressure is shown in Fig. 4. Experiment was repeated both in increase and decreasing modes for several times and the standard deviation curve for six observations is shown in Fig. 6. In the second step the output of the pressure transmitter is taken in terms of current signal and he characteristic is shown in Fig. 7. pic Fig. 4 Characteristic graph obtained by plotting Hall voltage against Pressure pic Fig. 5 Percentage deviation Curve of the Hall Probe based Pressure Transducer picFig. 6 Standard Deviation Curve of the Hall Probe based Pressure Transducer pic Fig. 7 Characteristic graph of hall probe based pressure transmitter V. DISCUSSION The characteristic of hall probe sensor is nonlinear in nature. But change of hall probe voltage is quite linear as shown in Fig. 4. The linear nature of the curve is due to the fact that the movement of the tip of the bellows for the entire pressure range is generally very small and hall probe voltage due to small change of distance between hall probe and magnet lies almost in the linear zone.The region deviation curves from linearity as shown in Fig 5 also indicate that the percentage deviation from linearity also lies within the tolerant limit. A very good repeatability of the experimental data was also observed as shown by the standard deviation curves in Figs. 6. The characteristic of the all told transmitter is almost linear as shown in Fig 7. The design of the system is very simple and the hall probe &038 the permanent magnet are now available at a very low cost. Hence the cost of the pressure transmitter will be low. References 1 J. P. Bentley, Principles of amount Systems, 3rd ed. Longman Singapore Publishers (pvt) Ltd. , Singapore, 1995. 2 E. O. Doeblin, Measurement System Application and Design, 4th ed. , McGraw-Hill, revolutionary York, 1990. 3 B. G. Liptak, Process Measurement and Analysis, 3rd ed. , U. K. Butterworth Heinman, Oxford, 1999. 4 D. M. Considine, Process Instruments and Control Hand Book, second ed. , McGraw-Hill, New York, 1974. 5 Raveendran, B. Subhash, K. M. Design of modular pressure transmitter with wireless susceptibility IEEE congregation on Electrical, Electronics and Computer Science (SCEECS), 2012, pp 1 3 6 Bera, S. C. Mandal, N. Sarkar, R. dissect of a Pressure Transmitter Using an Improved Inductance straddle Network and Bourdon Tube as Transducer IEEE Transactions on orchestration and Measurement, Vol 60 , Issue 4 , Year 2011 , pp 1453 1460 7 Yaocan Ruan Minghao He Shuran Song Tiansheng Hong Multipoint wireless pressure detecting system 2nd International Conference on Artificial Intelligence, Management Science and Electronic Commerce (AIMSEC), 2011 IEEE Conference, 2011 , PP 4091 4094 8 Zeng Mingru You Wentang Qian Xin , The development of intelligent pressure transmitter based on HART Protocol IEEE Conference on E-Health Networking, Digital Eco systems and Technologies (EDT), Vol. , 2010 , pp 121 124 9 Kanakasabapathi Subramanian, Jeffrey B. Fortin, and Kuna Kishore, Scalable vertical diaphragm pressure sensors device and process design, design for packaging IEEE Sensors Journal. , vol. 6, no. 3, June 2006, pp. 618-622 10 S. Y. Yurish, Intelligent digital pressure sensors and transducers based on universal frequency-to-digital converters (UFDC-1), Sensors &038 Transducers Journal. , vol. 60, no. 10, October 2005, pp. 432-438. 11 Radimir Vrba, Miroslav Sveda and Karel Marecek, Pressure transducer with multiplexed frequency transmitter, Slconi04 Seoron for industry Conference, New Orleans, Louisiaiib, USA, 27th -29th January, 2004, pp. 07-10.