AWARDEE OF TECHNOLOGICAL SCIENCES PRIZE

ZHANG ZHONGHUA

Zhang Zhonghua, an expert in the Metrology field, was born in July 1940 in Suzhou of Jiangsu Province. He graduated from the Electrical Engineering Department of Postgraduate School of Tsinhua University in 1965. Subsequently he joined National Institute of Metrology (NIM) and worked in the field of precise electrical measurement. He was elected the academician of Chinese Academy of Engineering in 1995.
From 1965 to 1979 he was responsible for establishing the capacitance standards by the Cross Capacitor method. This standard reached 1×10-7uncertainty and was approved as the National Primary Standard. In 1997 the National Standard of Capacitance participated the international 10pF capacitance comparison organized by Bureau International des Poids et Mesures and only a 0.04ppm deviation from the international mean value was found, which is belong to the best ones in the world.
From 1983 to 1988 Zhang Zhonghua was responsible for establishing the National Standard of High Magnetic Field (2-12Tesla, 60ppm uncertainty) with the cryogenic Nuclear Magnetic Resonance method to meet the requirement of calibration and test of the super-conducting magnet system, as well as the high magnetic field meters. He invented a special “Suppression Method” to overcome the difficulty of transmitting the high frequency cryogenic NMR signal through the necessary long probe rod from the center of magnet in cryostat. Up to now, this system is still one of the best similar systems in the world. Zhang Zhonghua got the 2nd grade national award for science and technology achievement of 1992 due to his contribution to establishing the National Standard of High Magnetic Field.
From 1987 to 2002 Zhang Zhonghua was turned to the establishing the Quantum Hall Resistance Standard. One of key points of this work is the cryogenic current comparator (ccc), which compares the resistance value of QHR (12906.4035ohm) with 100ohm. In 2002 Zhang Zhonghua and his group completed a ccc with uncertainty less than 0.001ppm, which is the highest one in the world. A series of laboratories of other countries (Italy, Denmark, South Korea, etc.) invite Zhang Zhonghua to give his lecture and cooperation for their similar work. The Chinese Instrument and Control Society gave the science and technology awards of 2001 to Zhang Zhonghua for his contribution to the fundamental electrical measurement standards.
The discovery of Quantum Hall Effect offers a different approach to determine the fine structure constant α by an experiment of macro quantum effect in semiconductor. Zhang Zhonghua did this determination by measuring the Quantum Hall resistance by the Cross-Capacitor, which was established by him in NIM, and submitted his experiment result to the CODATA. In the latest CODATA Recommended Values of the Fundamental Physical Constants (J. Phys. Chem. Ref. Data, vol. 28, No.6, p.1766), the result given by Zhang Zhonghua is used as one of four results from different countries. Now Zhang Zhonghua becomes a member of the CODATA Task Group on Fundamental Constants now.