METLAB
METLAB  LABORATORY OF PRECISE MEASUREMENT OF ELECTRICAL QUANTITIES Address: Technická 2, 166 27 Prague 6, Czech Republic Phone: +420224352173, Fax: +420233339929 
Members of METLAB
Prof. Ing. Jaroslav Boháček, DrSc.











What research are we doing?
Since 1993, increased attention has been paid to investigating the metrological applicability of the AC quantum Hall effect (QHE). After finding that the unit of resistance can be reproduced by means of AlGaAs/GaAs heterostructure devices with an uncertainty of the order of 1 part in 10^{7} over a frequency range from DC to at least 5 kHz, a number of metrological laboratories started to use these devices as reference standards in AC calibrations of resistance and, later, also capacitance standards.
In the Czech Republic, the problems of AC QHEbased impedance calibrations have been solved within the framework of three projects supported by the Grant Agency of the Czech Republic and coordinated by our department. In addition to standards and bridges for resistance and capacitance calibrations, facilities for calibrating standards of self and mutual inductance have been developed. At present, the main attention is paid to increasing the frequency range, in which the calibrations are made.
What is the purpose of our research?
Our present research is devoted to problems of precision measurements of various electrical quantities. Standards, bridges, and procedures for a newly formed system for primary calibrations of impedance standards are being developed, attention being also paid to calibrations of precision wideband LCR meters and to design and calibrations of shunts for high currents.
What are we specifically concerned with?
A.Special standards
 Calculable resistance and capacitance standards
Calculable standards of various designs (coaxial, quadrifilar and octofilar resistors) have been realized for precision measurements of frequency dependences of both conventional and quantum resistance standards.

Transfer standards
10 × 100 Ω and 10 × 1000 Ω Hamon transfer standards for a frequency range up to 5 kHz have been realized to be used in precision measurements of resistance ratios and in calibrations of inductive voltage dividers.
B.Special measuring devices and their modular units:

Electronic modular units of special measuring devices (2 channel compensation unit)
In case of need, such units (e.g. precision voltage followers or electronic compensators of unwanted voltage drops) can be used to improve metrological characteristics of measuring devices.

Reference divider formed by permuted capacitors.
This divider is intended for calibrations of inductively coupled ratio arms of bridges for 1:10 comparisons of resistance or capacitance standards.
 Ratio arms of highfrequency bridges
With an intention to find an optimum way of winding, several versions of 1:10 inductively coupled ratio arms have been prepared and calibrated by comparison with the above reference capacitance divider.
 Digitally controlled 6bit inductive voltage dividers
These units can serve as balance controls of highfrequency bridges.
Who supports our research financially?
Our research is funded by the Czech Office for Standards, Metrology, and Testing in the framework of the Metrology Development Programme. In past, our research was funded from the MSM6840770015 Programme of the Ministry of Education, Youth, and Sports of the Czech Republic.
Who do we collaborate with?
 We fabricate special standards for foreign metrology institutes:
 we realized a 12906,4 Ω calculable resistance standard for the PhysikalischeTechnische Bundesanstalt in Braunschweig in the framework of research activity 5.2 of the European SMT project "Modular System for the Calibration of Capacitance Standards Based on the Quantum Hall Effect".
 we realized 100 Ω a 1000 Ω calculable resistance standards for Glówny Urziad Miar in Warsaw.
 we realized 100 Ω a 1000 Ω calculable resistance standards for Istituto Nazionale di Ricerca Metrologica in Turin.
 we realized a quadrifilar resistor standard QR38700 Ω in cooperation CMI for PTB Braunschweig
 we realized a quadrifilar resistor standard QR12 906,4 Ω in cooperation CMI for KRISS
 we participate in international EURAMET comparisons:
 Comparison No. 432 "Frequency Performance of 12906.4 Ω and 6453.2 Ω Reference Resistors for AC Quantum Hall Effect Experiments" (coordination)
 Comparison No. 607 "100 mH Inductance Intercomparison"
We established mutually beneficial liaisons with a number of foreign metrology institutions. Papers prepared jointly with the following institutions have been published:
 PhysikalischTechnische Bundesanstalt, Braunschweig, Germany
 National Physical Laboratory, Teddington, United Kingdom
 Bureau International des Poids et Mesures, Sèvres, France
 Electrotechnical Laboratory, Tsukuba, Japan
 National Research Council, Ottawa, Canada
 Istituto Nazionale di Ricerca Metrologica, Turin, Italy
 National Metrology Laboratory, Pretoria, South Africa
Selected publications
 Hartland A.  Kibble B. P.  Rodgers P. J.  Boháček J.: AC Measurements of the Quantized Hall Resistance. IEEE Trans. Instr. Meas., 1995, sv. 44, č. 2, str. 245248.
 Boháček J.  Svoboda P.  Vašek P.: AC QHEBased Calibration of Resistance Standards. IEEE Trans. Instr. Meas., 1997, sv. 46, č. 2, str. 273275.
 Boháček J.: AC QHEBased Resistance and Capacitance Calibrations. IEE Proc.Sci. Meas. Technol., 2000, sv. 147, č. 4, str. 190192.
 Boháček J.  Wood B. M.: Octofilar Resistors with Calculable Frequency Dependence. Metrologia, 2001, sv. 38, č. 3, str. 241247.
 Boháček J.: EUROMET Project 432: Frequency Performance of 12906 Ω and 6453 Ω Reference Resistors for AC Quantum Hall Effect Experiments. Metrologia, 2002, sv. 39, č. 2, str.231237.
 Melcher J.  Schurr J.  Pierz K.  Williams J. M.  Giblin S. P.  Cabiati F.  Callegaro L.  MarulloReedtz G.  Cassiago C.  Jeckelmann B.  Jeanneret B.  Overnay F.  Boháček J.  Říha J.  Power O.  Murray J.  Nunes M.  Lobo M.  Godinho I.: The European ACQHE Project: Modular System for the Calibration of Capacitance Standards Based on the Quantum Hall Effect. IEEE Trans. Instr. Meas., 2003, sv. 52, č. 2, str. 563568.
 Boháček J.: A QHEBased System for Calibrating Impedance Standards. IEEE Trans. Instr. Meas., 2004, sv. 53, č. 4, str. 977980.
 Callegaro L.  D´Elia V.  Boháček J.: FourTerminalPair Inductance Comparison Between INRIM and CTU. IEEE Trans. Instr. Meas., 2009, sv. 58, č. 1, str. 8793.
 Sedláček R.  Boháček J.: Bridges for Calibrating FourTerminalPair Standards of SelfInductance at Frequencies up to 10 kHz. Meas. Sci. Technol. 20 (2009) 025105, doi: 10.1088/09570233/20/2/025105.
 Kučera J.  Vollmer E.  Schurr J.  Boháček J.: Calculable Resistors of Coaxial Design. Meas. Sci. Technol. 20 (2009) 095104, doi: 10.1088/09570233/20/9/095104.
 Kučera J.  Sedláček R.  Boháček J.: A New Capacitance Device for Calibration of N:1 HF Inductive Voltage Dividers. 2010 Conference on Precision Electromagnetic Measurements Digest, pp. 390391. IEEE, Daejeon 2010. ISBN 978142445.
 Boháček J.  Horská J.  Sedláček R.: Comparison of Frequency Dependences of Resistance Standards Made from Surface Mount Resistors. 2010 Conference on Precision Electromagnetic Measurements Digest, pp. 647648. IEEE, Daejeon 2010. ISBN 978142445.