Kare Lind

Design, Modeling, and Verification of High-Performance AC–DC Current Shunts From Inexpensive Components

A new type of AC current shunt for AC-DC current transfer is presented for which the AC-DC current differences at frequencies from 10 to 100 kHz are calculated with uncertainties smaller than plusmn 9 muA/A in the current range of 30 mA-10 A. This is an independent realization of the AC-DC current-transfer standards in addition to the step-up method used at most National Metrology Institutes. The construction, modeling, and experimental verification of the shunts are described.

Phase Comparison of High-Current Shunts up to 100 kHz

A comparison of the phase error of existing shunts for currents between 10 and 100 A and frequencies from 500 Hz to 100 kHz has been organized. Measurement processes were performed at Istituto Nationale di Ricerca Metrologica on some shunts using the first prototype of a new type of a phase comparator and a step-up method for data processing. Results of the relative measurement processes have shown good repeatability. The method for evaluation of reference values was based on similar shunts and suitable assumptions and derived by extrapolation. For the type of resistance elements employed in these shunts, the derivation of the reference is not very accurate and still needs to be improved.

Phase comparison of high current shunts up to 100 kHz

A comparison of the phase of existing shunts for currents between 10 A and 100 A and frequencies from 500 Hz to 100 kHz has been organized. The measurements were performed at INRIM using a first prototype of a new type of phase comparator and a step-up method for the data processing. The results of the relative measurements have shown a good repeatability, but the method for the evaluation of the reference value still needs some improvement.

A precision setup and method for calibrating a DC voltage divider's ratios from 10 V to 1000 V

A precision set-up and method for calibrating the division ratios of a resistive divider for DC-voltage in the range 10 V to 1000 V is described. The method requires equipment commonly available in most standard laboratories. Uncertainties better than 3/spl times/10/sup -7/ (k = 2) in the ratio is achieved.

A survey of current shunts for ac power measurements

This paper gives a survey of the performance of existing current shunts designed by National Metrology Institutes (NMIs) around Europe. Key characteristics for power measurement; phase displacement, ac-dc transfer difference and power coefficient of the shunt resistance is reported for 5A, 50 A and 100 A shunts.

AN OPTOELECTRONIC COUPLING FOR PULSE-DRIVEN JOSEPHSON JUNCTION ARRAYS

The optoelectronic coupling for a pulse-driven Josephson junction array (JJA) for use as a quantum voltage synthesizer has been designed. This system uses optoelectronic components to drive a group of JJAs in parallel. Since the drive system is electrically isolated from the JJAs, they can be connected in series, leading to a higher output voltage. A thin film circuit, including interdigitated capacitors to couple a photodiode to the JJAs has been designed and tested and shown to meet the design goals.

Low-cost high-performance current shunts — improved design for 30 mA – 100 mA

A new and improved design of the JV current shunts for 30 to 100 mA has been developed. The new shunts use surface-mount resistors mounted in a star configuration. AC-DC difference less than 3 muA/A at 100 kHz and less than 5 muA/A at 300 kHz has been achieved. Calculated and measured values agree very well.

Development of high precision voltage dividers and buffer for AC voltage metrology up to 1 MHz

A voltage divider and buffer system has been proposed in order to improve the AC Voltage traceability at Justervesenet (JV) for frequencies up to 1 MHz. The buffer is constructed with the intention to drive any heavy load impedance. Simulations suggest that AC-DC difference span less than 30 ppm for frequencies up to 1 MHz for both divider and buffer.

Simulation and development of high precision Voltage dividers and buffer for AC voltage metrology up to 1 MHz

A voltage divider and buffer system has been proposed in order to improve the AC Voltage traceability at Justervesenet (JV) for frequencies up to 1 MHz. Buffer prototypes have been constructed for use at room temperature and liquid nitrogen. They have proven ability to operate up to 1 MHz with a 50 Ω load at 300 K and beyond 10 MHz for loads above 1 kΩ. Simulations suggest that AC-DC difference span less than 30 ppm for frequencies up to 1 MHz for the divider and 200 ppm for the buffer. Although there are some discrepancies between buffer simulation and prototype measurements, the model still possess great explanatory power.

Photodiodes as current source in high-frequency low temperature applications

Prospects of exploiting photodiodes as a high frequency current source for low temperature applications is presented. The source will be implemented in the AC Josephson Standard of the Q-Wave project within the European Metrology Research Programme. Method for optically biasing the diodes is described and some initial results of photocurrent measurements at 4K indicates that high frequency ~28 GHz photodiodes could be exploited as current source for Josephson Arbitrary Waveform Standard.