This article has been accepted for inclusion in a future issue of this journal. Content is final as presented, with the exception of pagination. IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT 1 Design and Development of an Electro-Optic Type-Flow Transmitter Using Mach–Zehnder Interferometer Brajesh Kumar, Saikat Kumar Bera, and Nirupama Mandal, Member, IEEE Abstract— The rotameter, the widely used flow meter, is generally used as a local indicator. Therefore, for industrial use, some necessary technique is required to transmit float displacement to remote location. Direct transmission of electrical signal through connecting wires is generally prohibited in an inflammable region. In this paper, an electro-optic system is devel- oped using a modified inductive-type rotameter, which produces an electrical signal according to float movement of the rotameter. The electrical signal is then converted into an optical signal using the Mach–Zhender interferometer. Necessary equations along with the developed theory of operation are presented in this paper. An experiment is performed on the proposed transmitter and the experimental and simulation results are reported in this paper. Very good linearity and repeatability with a very small uncertainty in the measurement of the transducer characteristic have been observed. The graphical abstract is shown. Index Terms— Electro-optic, ferromagnetic wire, float, induc- tive pickup, Mach–Zehnder interferometer (MZI), rotameter, transducer. I. I NTRODUCTION M EASUREMENT of liquid flow rate is an important process variable for process industries. In process industries, like petrochemical, oil, and power industries, the flow rate is measured at one point and it has to be trans- mitted to a remote location for further processing. We need some transducer that converts the flow variable into a usable signal that can be transmitted to a remote location without or negligible transmission loss for further processing. Thus, the flow transducer is a vital part of the system, and its performance determines the reliability and accuracy of the operation [1]–[5], [19], [20] of the whole flow monitoring system. Many works on the development and application of new and modified techniques for the flow measurement of a single-phase or two-phase fluid have been reported by various researchers. Wang and Wang [6] have developed a microfluidic particle image velocimetry technique for the mea- surement of water flow rate in microchannel scale. In general, an electromagnetic flow meter is used for the measurement Manuscript received September 21, 2015; revised February 22, 2016; accepted February 24, 2016. This work was supported by the Ministry of Human Resource Development, Government of India. The Associate Editor coordinating the review process was Dr. Yong Yan. B. Kumar and N. Mandal are with the Department of Electronics Engineering, Indian School of Mines, Dhanbad 826004, India (e-mail: brajesh.nitrkl@gmail.com; nirupma_cal@rediffmail.com). S. K. Bera is with Government Engineering College at Chaibasa, Chaibasa 833201, India (e-mail: skb392@rediffmail.com). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TIM.2016.2540886 of conducting liquid. An electromagnetic flow meter requires a magnetization coil and a set of sensing electrodes, which increase the size and cost of flow head of the flow meter. To overcome this problem, Bera and Chakraborty [7] have described a novel low-cost bridge technique of flow mea- surement for a conducting liquid. Abou-Arkoub et al. [9] have investigated a capacitance sensing technique for multi- phase flow meters. This capacitance sensing technique that combines with the statistical and fuzzy classification method can easily determine the carrier, phase, and flow regime in a range of multiphase flows. The flow rate of conducting liquid can be measured by a polarization-impedance-type flow transducer. In the polarization-impedance-type flow transducer, the excitation frequency, current density, and flow rate of con- ducting liquid nonlinearly vary with polarization impedance. Bera et al. [10] have studied the effect of excitation frequency on the output of electrode polarization-impedance-type flow transducer. In this study, a theoretical analysis and an experi- mental analysis have been presented on the nonlinear depen- dence of the flow transducer output with excitation frequency. Skinner et al. [12] have described a null-buoyancy thermal flow sensor for the measurement of very slow downward fluid flows. This sensor has been used at the core of an alternative parametric design itself. Bera and Mandal [15] have described a noncontact capacitance-type orifice transducer for the mea- surement of flow rate without a Differential Pressure cell. Marick et al. [18] have developed a modified differential- inductance-type flow transducer that consists of two identical Bourdon tubes as the primary sensing elements to measure small changes in pressure due to the flow of fluid in the horizontal pipeline. Mandal et al. [19] have designed and tested the self-inductance-type rotameter transducer for the flow of liquid measurement. Here, the movement of the float is converted into inductance, which is measured by a modified Maxwell bridge. The bridge output voltage relates to the flow of liquid using the signal conditioning circuit and instrumen- tation amplifiers. Sinha et al. [21] have designed, developed, and tested the flow transmitter technique using rotameter and a Hall probe sensor. In this technique, the Hall probe sensor is placed outside of the rotameter tube to sense the variation of the magnetic field. For the variation of magnetic field, a thin circular permanent magnet has been attached to the float. In order to send the value of flow rate to a remote location, the signal is transmitted in the form of an electrical signal. However, if the transmitting path is through the inflammable and hazardous area, then the electrical signal transmission may 0018-9456 © 2016 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.