100 mV acdc Transfer Standard Measurements with a Pulse-Driven AC Josephson Voltage Standard

In order to improve the low-voltage calibration service at NIST, we have constructed an ac Josephson voltage standard system with a maximum rms output voltage of 100 mV. Using this system, we synthesized sinewaves of various audio frequencies and measured ac-dc differences on the 220 mV range of a commercial thermal transfer standard. By modifying the output resistance of the low-pass-filtered transmission line, we were able to extend our measurement frequency from a few kilohertz up to 100 kHz. Our data are well within the uncertainty budget of ac-dc difference calibrations made of this transfer standard using conventional techniques. At the conference, we will present additional results using new Josephson circuits capable of reaching 200 mV.