Design and metrological applications of a low noise, high electrical isolation measurement unit

A digitally controlled voltage generation and measurement unit optimised for high-precision electrical metrology is described. It is optically isolated from the controlling computer and contains specially constructed isolated power supplies allowing continuous operation without the need to recharge batteries. The source has a simple microcontroller that is pre-programmed with firmware to control operation and to carry out simple repetitive measurement tasks, such as generation and quantisation of signals using uniform sampling. The merits of the developed unit are demonstrated by three example applications: (i) the application of the unit to control a Josephson voltage standard, (ii) the implementation of a transfer standard for the calibration of the electronic instrumentation of fatigue testing machines traceable to the primary electrical standards and (iii) the force measurement of an ion thruster traceable to the primary electrical standards at the industrial user level.