Zhang Zhonghua was born in China in 1940. He graduated from the Electrical Engineering Department of Postgraduate School of Tsinhua University, Beijing, China in 1965. Subsequently he joined the Electromagnetic Division of National Institute of Metrology (NIM) and worked in the field of precise electrical measurement. His major work in this field is as follows.
In 1965 he was responsible for the establishing the capacitance standards by the Cross-Capacitor method. This work was completed in 1979. The standard reached 0.1ppm uncertainty and was approved as the National Primary Standard. After establishment this National Capacitance Standard filled the requirement of disseminating the standard value of ac impedance (capacitance, inductance, ac resistance etc.) and verification work for the whole country more than 20 years. In 1980 and 1997 the National Standard of Capacitance participated the international 10pF capacitance comparison organized by Bureau International des Poids et Mesures (BIPM, i.e. the international central metrology institute) and satisfactory results was obtained. In 1997’s comparison, only a 0.04ppm deviation from the international mean value, which is below its 0.1ppm uncertainty, was found and belong to the best ones. Zhang Zhonghua got the 3rd grade national award for science and technology achievement of 1995 due to his contribution to establishing the National Standard of Capacitance.
From 1983 to 1988 Zhang Zhonghua was responsible for establishing the National Standard of High Magnetic Field (2-12Tesla, 60ppm uncertainty) by 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 2003 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 2003 Zhang Zhonghua and his group completed a ccc with uncertainty less than 0.00024ppm, which is the highest one in the world up to now. 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. In 2003, he got the Ho Leung Ho Lee award of technological sciences. In 2007, Zhang Zhonghua got the 1st grade national award for science and technology achievement due to his contribution to establishing the QHR Standard of NIM.
From 2005, Zhang Zhonghua turned his activity to the Watt Balance method. It is a long term project and will be going on for 10 years.
The precise measurement and standards has a close relation to the problem of determination of fundamental physical constants. For example, the fine structure constant ??is proportional to the Quantum Hall resistance. The discovery of Quantum Hall Effect offers an additional manner to determine the fine structure constant ??by an experiment of macro quantum effect in semiconductor. Therefore, it is interesting to determine the fine structure constant ? by Quantum Hall resistance. Zhang Zhonghua did this determination of 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 (Rev. Of Modern Phys. vol. 08, No.2, p.1766), the result given by Zhang Zhonghua is used as one of five results from different countries. Now Zhang Zhonghua is a member of the CODATA Task Group on Fundamental Constants.
Considering the contribution of Zhang Zhonghua to the precise electrical measurement in long term, he was elected as a member of Chinese Engineering Academy in 1995. In 2003, he got the Ho Leung Ho Lee award of technological sciences of 2003. In addition, he was invited as a guest professor of a series of famous Chinese universities, such as Tsinghua University, Tianjin University, Harbin Technical University, Xian Communication University, Beihang University, Hebei University, Qingdao University, etc..