Complete Characterization of a Low Thermal Scanner for Automatic Voltage Measurement

In order to increase the capacity of the National Institute of Standards and Technology (NIST) 10V Josephson Voltage Standard (JVS) system used for the automatic calibration of Zener reference standards from the present 32 channels, a 64 channel low thermal scanner was procured. There are four ways for the characterization of low thermal scanner depending on application. The scanner has been characterized in all the four ways but more emphasis has been given for its application in NIST JVS system and group of Standard cells / Zener Reference Standards calibration. The results of this characterization are of consistent with requirement of JVS system and group of Standard cells calibration. In the NIST JVS system, the scanner output lines are cross-connected to compensate the thermal emf of the scanner channels. The new scanner has been fully characterized in this mode to simulate the same measurement condition used in the "NISTVolt" software that performs the automatic calibration of Zener standards. The results of this characterization show that thermal emfs of the scanner channels are well within the required 50 nV for the JVS application. The 64 channel scanner was installed in the NIST 10 V Josephson Voltage Standard system and used to calibrate Zener reference standards