Ratio calibration of a digital voltmeter (DVM) is critical for some applications such as load cell response for force measurement. The NIST DVM ratio service has provided ratio voltage measurements that are traceable to the Josephson Voltage Standard (JVS). Previously, the service was supported by NIST JVS systems using manual measurements. The NIST JVS uses a conventional Josephson junction array which often experiences a spontaneous step transition, caused by electromagnetic interference, during its operation. An adjustment is required to obtain a stable voltage step for the ratio calibration. The programmable JVS (PJVS), developed in the last decade, uses an array with non-hysteretic steps to provide a stable voltage. The PJVS was implemented in the DVM ratio calibration service to improve the efficiency and reliability of the service. The new protocol can be executed automatically to reduce the labor cost of the calibration service. The uncertainty of the DVM ratio calibration can be improved by taking automatic multiple measurements. This paper describes the DVM ratio calibration procedure and compares the conventional JVS and PJVS protocols. Results of an actual DVM ratio calibration are presented.
Pub Type: Journals
automation, digital voltmeter, force measurement, Josephson voltage standard, programmable Josephson voltage standard, ratio calibration, uncertainty