Multijunction Thermal Converters:
Multijunction Thermal Converters (MJTCs) are the most accurate devices for the measurement of ac current and voltage, and have been used as primary standards at NIST and other National Metrology Institutes for many years. In spite of their inherent accuracy, traditional MJTCs constructed from discreet wires are expensive (when even available), delicate, and difficult to use. However, MJTCs made using semiconductor fabrication techniques can be made fairly cheaply, and are much more rugged than wire MJTCs, but have the same accuracy over wider frequency and voltage ranges.
The AC-DC Project has been developing thin-film MJTCS for several years. The working standards we use in our calibration service for ac-dc difference of voltage were developed in collaboration with Sandia National Laboratories. These devices have been proven to be as accurate as our wire primary standards with almost negligible voltage coefficients over their working range of 200 mV to 2 V. We have supplied these devices to the primary standards laboratories of the U.S. Department of Defense, as well as to Sandia National Laboratories, and to Kennedy Space Center.
We are presently developing MJTCs for use as current standards up to 1 A on a single chip, and 10 A using 8 chips in parallel, and anticipate introducing these devices into routine use within the next year. Our latest chip is the world's best 1 A current converter. To read more about it, click here.
We are also designing and fabricating MJTCs on quartz substrates with very small ac-dc differences up to 100 MHz, and we anticipate that with some design modifications we can fabricate a chip with excellent characteristics at 1 GHz.