Prototype of a Compact Detachable Zener Module for DC Voltage Standard

We have been developing a compact Zener voltage generating system as a secondary standard of DC voltage. The main unit of the system includes a temperature-controlled Zener diode module driven with a built-in battery. The module is detachable from an expansion unit with larger battery packs for longer-time battery operation. This system realizes a compact DC voltage standard with maintaining state-of-the-art temporal stability and temperature stability performances of the output voltage. The results of the precise measurements based on a Josephson voltage standard show excellent drift characteristics within 2 ppm/year, small temperature coefficient less than 0.01 ppm/°C and negligible pressure coefficient. This DC voltage standard can be used in laboratories, inter-laboratory comparisons, and beyond such conventional purposes, the main Zener diode module can be installed in a measurement devices, such as digital multimeters, for further improvement of measurement capabilities.