Practical scanner for voltage metrology

A switching device with low thermal electromotive forces is a core apparatus in all voltage standard laboratories where the unit must be maintained with high accuracy. Switching is essential in the pair intercomparison measurements required to maintain a voltage standard with multiple references and for the dissemination of the unit. Although various low- thermal switching equipment are available commercially, most of them are not suited for voltage metrology, making it difficult to find an acceptable tradeoff between, accuracy, cost, reliability and ease of use. In the following a prototype of a practical USB-controlled device for low thermal interconnection and polarity reversal of reference standards is described.