A rotameter is a variable area type flow rate measuring instrument in which the position of a metallic float in a transparent conical tube is taken as a flow rate indicator. It has the disadvantage that it is a local indicating type instrument and special type of transducer is used for its remote indication. In the present paper, a non-contact flow rate measurement technique using Hall probe sensor and rotameter is designed, developed and tested. In this design, a float carrying a thin circular permanent magnet is used and a Hall probe sensor placed outside the rotameter tube has been used to sense the variation of magnetic field of the magnet with the variation of float position. A signal conditioner unit has been used to convert the Hall probe sensor output into 1-5 volt dc signal. This dc signal output of the signal conditioner has been sent to a PC based flow indicator through opto-isolator and analog input channel of a data acquisition system (DAS) card. The PC based flow indicator has been designed using Lab Tech Note Book Pro software and PC based supervisory control and data acquisition (SCADA) system. A theoretical equation has been derived to explain the operation of the system. The performance of the system has been tested experimentally and the experimental results are reported in the paper. A very good repeatability and linearity of results has been observed. Graphical Abstract:Index Terms-Flow Measurement, Hall Probe, Process Monitoring, PC based SCADA, Rotameter.1530-437X (c)

Bellows is an elastic-type pressure sensor used as a local indicator in industry. Transmission of bellows reading to a remote location in control room is very important in pressure measurement and control system in industry. In this paper, the design of a noncontact pressure transducer along with a transmitting unit using bellows as the primary sensing element and a Hall sensor as secondary sensing element has been described. The theoretical equations describing the operation of the proposed transducer and transmitter have been derived. The function of the transducer and transmitter has been experimentally tested and the experimental results are reported in the paper. Both transducer and transmitter characteristics have been found to be linear with good repeatability. The graphical abstract is shown in Fig. 1.Index Terms-Bellows, Hall sensor, noncontact technique, pressure transducer, pressure transmitter.