Development of a Digital Multimeter with Removable Voltage Reference

We are developing a digital multimeter (DMM) system with a new concept of a removable voltage reference. In this system, the voltage reference in a DMM can be detached from the DMM chassis, used as a portable Zener voltage standard, and calibrated by using other reference voltage standards. This concept enables easy and advanced traceability of DMMs with lower maintenance costs. This paper presents the DMM prototype and the preliminary result of an experiment related to the drift characteristics of the gain error.