R. Sarkar, Animesh Ghosh, Lipika Ghosh and N. Mandal
Asansol Engineering College
Vivekananda Sarani, Kanyapur, Asansol-713305
E-mail: firstname.lastname@example.org, email@example.com, firstname.lastname@example.org
Abstract: Bellows, an elastic type pressure sensor is generally used as a local indicator. To transmit the signal of bellows to a remote distance some technique is needed. In the present paper a Hall probe sensor has been used to convert the bellows movement into voltage signal which can be converted into 4 – 20 mA current signal and transmitted to a remote indicator. It has been observed that the transducer and transmitter outputs against pressure have a very good linearity and repeatability. The necessary theoretical equations along with experimental results are reported in the paper.
Keywords: pressure measurement, bellows, Pressure transmitter, Magnet, Hall Probe.
Pressure is an important measuring and controlling technical parameter during industrial production process. In order to operate industrial production well, pressure should be accurately measured and controlled. Pressure can be measured in terms of absolute or gauge. The absolute pressure can be measured in terms of height of a liquid column in a manometer whereas the gauge pressure is measured by different types of sensors [1-4]. As for example bourdon tube, diaphragm, capsule, bellow element etc. operate as primary sensing elements for measuring positive or negative gauge pressure. The sensors like strain gauge, piezoresistance, LVDT, capacitive element, inductive element etc. act as secondary sensors to measure positive or negative gauge pressure. The negative gauge pressure or vacuum pressure can also be measured by many other sensors like pirani gauge, ionization gauge, McLeod gauge etc. In industrial 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 using 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 works on development of reliable pressure transducer are still being reported by different groups of workers. B. Raveendran et al.  have designed and developed a MEMS based wireless modular pressure transmitter. A Bourdon tube based pressure transmitter unit using an improved inductance bridge network has been studied by S.C.Bera et al. . Y. Ruan et al.  have developed a multipoint wireless pressure transmitting system composed of pressure sensor PTB203, A/D converter ADC0804, MCU STC89C52, wireless communication module CC1101, receiver module STC89C52, CC1101 and display module LCD1602. Zeng Mingru et al.  have developed a HART Protocol based intelligent pressure transmitter which is compatible with both analog and digital signals. K.Subramanian et al.  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  to develop an intelligent digital pressure transducer. A multiplexed frequency transmitter technique has been used by R.Vrba et al.  to design a reliable pressure transducer using ceramic diaphragm. In the present paper, a hall probe based pressure measurement technique has been developed. In this technique a permanent magnet is placed on the tip of the bellows with the Hall probe sensor on the top of the outside fitting of bellows chamber as shown in Fig.1. The movement of the bellows tip is measured by a hall probe sensor. With the change of pressure the distance between magnet and...