A High Accuracy Automated Measuring System for Standard-Cell Comparison

Described is an automated standard-cell measurement system capable of reaching a 10-nV resolution. A commercial low-cost Basic programmable microcomputer as a controller, two dc motor-driven low-thermal-electromotive force (EMF) multipole switches for standard-cell selection, and a high sensitivity digital nanovoltmeter as the voltage difference measuring device, together with some dedicated and special interface circuitry, provides the basis for the system. Great care has been taken of appropriate screening and guarding to prevent unwanted interference between the digital and analog sections of the system. Great care has been taken of appropriate screening and guarding to prevent unwanted interference between the digital and analog sections of the system. One year´s experience has indicated that in comparing good standard cells a repeatability of 2·10-8 is normal on a day-to-day basis.