First measurements of the flux integral with the NIST-4 watt balance

TL;DR

This paper reports the initial measurements of the magnetic flux integral using the newly constructed NIST-4 watt balance, highlighting measurement techniques and the impact of vibrations on precision.

Contribution

It presents the first flux integral measurements with NIST-4 and introduces methods to evaluate measurement quality and vibration effects.

Findings

First flux integral measurements with NIST-4

Measurement techniques for flux integral assessment

Analysis of vibration effects on measurements

Abstract

In early 2014, construction of a new watt balance, named NIST-4, has started at the National Institute of Standards and Technology (NIST). In a watt balance, the gravitational force of an unknown mass is compensated by an electromagnetic force produced by a coil in a magnet system. The electromagnetic force depends on the current in the coil and the magnetic flux integral. Most watt balances feature an additional calibration mode, referred to as velocity mode, which allows one to measure the magnetic flux integral to high precision. In this article we describe first measurements of the flux integral in the new watt balance. We introduce measurement and data analysis techniques to assess the quality of the measurements and the adverse effects of vibrations on the instrument.