A bias source for the voltage reference of the BIPM watt balance

We have developed a programmable current bias source to set the voltage output of a Josephson Voltage Standard that will be operated on the watt balance experiment. The device has been designed to bias separately all of the 13 independent segments of the Josephson array in order to be able to track the induced voltage across the moving coil during the constant velocity and acceleration phases. It is powered from Lithium-ion batteries in order to avoid electrical offsets originating from ground loops and to allow long series of measurements.