DESIGN AND DEVELOPMENT OF PROGRAMMABLE FIELD INSTRUMENTS

摘要

A group of instruments can play central role in monitoring and controlling function of multiple parameters when interfaced to PC through various external standard interfaces or add-on cards. These standard interfaces include parallel port, serial port (RS232), universal synchronous bus (USB), ISA bus, PCI bus etc. Advantages of using such standard interfaces are manifold i.e. no separate interface or software is required, large number of instruments have in-built interfaces and efficient programs can be developed in high-level languages using available drivers. Modern analytical instruments are designed to operate in a standalone mode i.e. from the instrument panel and same instrument can also be interfaced to PC through standard interface for advance operation/programming. These trends of instrument development can be embedded in field instruments, which can be programmed for a desired set of features through PC and use it in the field for monitoring/controlling of certain parameter. The data acquired can be stored in the instrument itself for a quite long duration and also can be downloaded to Laptop/PC for further processing. In this paper, an attempt has been made to develop an intelligent programmable field instrument for monitoring environmental parameters in the field. This can be achieved in the following way, 1) Interfacing of signal conditioning module to PC/Lap-top through RS-485 2) Development of software in Visual Basic for programming field instruments, which can be downloaded from PC/Lap-top. 3) Selection of state-or-art hardware for communication from PC to field instrument via RS-485. 4) Facility to upload data to PC/Laptop. 5) Development of field re-configurable data acquisition system.