The Design For Micro-ohmmeter Based On LMS

It is common to measure micro-resistance for the quality and performance of equipment in engineering practice. However, this can't be done perfectly by the digital multimeter. So this paper presents a design solution of micro-ohmmeter. Besides, it also have simulated and tested for this design solution.The whole system is divided into two parts:the hardware system and the software system. The hardware system consists of a constant-current source circuit (CCSC), a signal processing circuit, A/D and D/A converter circuit, other peripheral circuits and the power module; the software system is mainly composed of the initialization subroutine, data collection subroutine, data processing subroutine and some interruption subroutine. Some key problems which restrict the measurement accuracy of micro-ohmmeter have been found in the process of design, and some solutions have been presented accordingly:Using four-wire measuring method to eliminate the wire resistance, improving the common CCSC for resistance matching problem, adopting LMS to filter noise, applying positive and negative current to remove the thermoelectric potential, presenting a simple way to weaken the influence of contact resistance in calibration effectively.