The National Institute of Standards and Technology (NIST) houses a room-sized electromechanical machine called the NIST-4 Kibble balance. The instrument can already measure the mass of objects of roughly 1 kilogram as accurately as any device in the world. But now, NIST researchers have used graphene to further improved their Kibble balance’s performance by adding to it a custom-built device that provides an exact definition of electrical resistance.
The device is called the quantum Hall array resistance standard (QHARS), and it consists of a set of several smaller devices that use a quirk of quantum physics to generate extremely precise amounts of electrical resistance. The improvement should help scientists use their balances to measure masses smaller than 1 kilogram with high accuracy, something no other Kibble balance has done before.