The Design Of Intelligent Field Process Calibrator

Due to the massive popularity of the production process automation technology,industrial systems use a large number of industrial process control instruments and systems.The process control instruments need inspection, and calibration at any time in order toguarantee the production process safe and reliable. The traditional method is to regularlydemolish the fixed-site installation instruments and do test and calibration in laboratory.Thisway makes instrumentation can not meet the requirements of the scene of periodicverification. It is necessary to develop a portable and high precision field process calibratorwhich is easy to operate and meets the industrial field instrumentation calibration accuracy.The paper designs an intelligent field process instrumentation calibrator, the accuracy ofthe basic range of the instrument up to0.02%, whose functions cover the calibration and testof a variety of electrical parameters signal in industrial control systems. Measurement andoutput functions both include: DC voltage, current, resistance, thermal resistance,thermocouple, frequency, pulse, switch and so on. Otherwise the instrument implanted thenecessary additional features for different functions, such as: cold junction compensation,loop power supply and other functions. As two independent and isolated channels,measurement and output allow simultaneous real-time to measure and output the signals.The paper firstly introduced the present development status of the process calibrator.Then according to the requirements of the design, it gives the general design of the processcalibrator. Starting from the function module, it detailed introduces the realization of theinstrument hardware and software. The instrument hardware circuit is huge, so there are manytechnical difficulties in design, such as the design of high-end constant current source inresistance measurement; resistance simulation to achieve; high efficiency isolated powersupply system; how to ensure that the millivolt small signal stability, low drift andinterference. Software discusses the achievement of each of main modules in the system inthe form of a flowchart. The paper studies the noise of the system and put forward a series of the anti-interference measures of software and hardware which effectively guaranteed theaccuracy of the instrument due to using the finite impulse response digital filtering and theautomatic real-time compensation technology in instrument in the software. Experimentalresults are given, and errors are analyzed. And finally it discusses the existing problems ofthis instrument and the improved direction in future.As a portable handheld field instrument, the paper designs the instrument who has asmall size, light weight, low power consumption, longer working hours and other features,which has a strong practical value.