After demonstrating bipolar waveforms in 2020, PTB's optical pulse transmission drive has been expanded for two independent Josephson junction arrays. Passive optical power splitters divide the two independent optical channels at room temperature. Balanced photodiodes modules in liquid helium then generate ternary electrical pulses to drive the nearby Josephson junction arrays via coplanar waveguides less than 10 mm long. The outputs of the Josephson junction arrays are connected in series and we successfully synthesized bipolar sinewaves at 1 kHz and 35 mV rms amplitude with higher harmonics suppressed by more than 96 dBc.
This paper describes briefly an electrostatic finite element simulation study of the imperfections of the LNE Thompson-Lampard calculable capacitor (TLCC) and their contributions to the standard's uncertainty. Thus, the limits of the accepted tolerances in order to achieve the target relative uncertainty of one part in 108 of the capacitance standard can be established. The simulation predictions are compared with experimental observations with the help of the sub-micron level control of the capacitor standard's electrode geometry.
This paper presents a cryocooled Josephson arbitrary waveform synthesizer (JAWS) developed at the National Institute of Metrology (NIM), China. A 2-volt Josephson junction chip is mounted on the second stage cold head of a cryostat. We develop a temperature controller to measure the output voltage of the temperature sensor, and control the temperature of the second-stage cold head. The controller is composed of a current source of high stability, relays, a preamplifier, a low pass filter and a 24-bit analog to digital converter, and a microcontroller unit. Preliminary results show that the cooling power at 4.2 K is about 279 mW and the temperature fluctuation is within 40 mK.
This paper introduces a quadratic weighted Fourier transform method based on quasi-synchronous sampling, which can solve the problems of transition process, Gibbs effect and asynchronous sampling when programmable Josephson quantum voltage standard is applied to harmonic voltage measurement by two different weighted and two step correction of the original signal obtained from differential sampling. According to the preliminary verification, when FLUKE 5700A is used as the voltage source, the standard deviation of the signal measurement results in the range of 1 kHz is consistent in the order of 10 -7 .
We report on the development of a new single-stage high-frequency inductive voltage divider (HF-IVD) for Quantum Hall Resistance measurements at frequencies up to 2 MHz. The design, construction and testing of the HF-IVD are detailed, including effects of switching on any spike voltages and settling times after switching are found to be only a few micro-seconds. Measurements over the 200 kHz to 2 MHz range show that both the in-phase and quadrature relative voltage deviations are less than 2% at 2 MHz. These measurements will also be compared to an electrical HF equivalent circuit model of the HF-IVD and presented at the CPEM 2024.
The first two impedance bridges based on pulse-driven Josephson voltage standards show the lowest uncertainties among digital bridges even comparable with state-of-the-art bridges using inductive voltage divider. In this paper, we will present the world's first comparison between these bridges. The observed difference between both systems measuring impedance ratios (C:C and R:R) is 6 nF/F and 6 n Omega/Omega at 1233.15 Hz. Up to 50 kHz, the measurements from both bridges agree within uncertainties, which are still below one part in 106 and dominated by cable effects.
We present the first steps taken towards a graphene quantum Hall effect ac resistance standard at RISE. A new measurement setup has been developed including a graphene quantum Hall effect device suitable for the kilohertz range and a coaxial cryoprobe to be used together with a coaxial impedance bridge based on inductive voltage dividers. 1:1 ratio resistance measurements of the graphene device against a 12.9 k Omega ac resistance standard resulted in a linear frequency dependent (approximate to 0.2 (mu O/O)/kHz) deviation from the quantized dc value.
Developing reliable standards for coaxial line systems in the AC-RF gap region has long proven to be challenging. In this work, the use of an N-type coaxial air line as an impedance standard at low frequencies is investigated through a comparison of measurements taken on an LCR meter from 0.1 kHz to 1 MHz with calculated values based on transmission line theory. The results demonstrate the viability of using such an air line as an impedance standard at frequencies below 1 MHz.
This contribution aims to describe the state of work of the new Kibble balance mechanism in the Quantum Electro-Mechanical Metrology Suite (QEMMS) at NIST. After experimental evaluation of a prototype flexure-based mechanism, upgrades have been incorporated in the design of a second version of the mechanism. These upgrades are mainly geared towards adjusting the linearity and direction of the mechanism trajectory, establishing the autostatic state, adjusting the static equilibrium condition plus stiffness in-vacuum, and rejecting external vibrations as much as possible. We hope to present measurements with the new design and put them in context with our improvements at the conference.
TWSTFT is a representative time comparison technique mostly using a bent-pipe transponder of a GEO satellite with Ku-band frequency. Conventionally, DS-BPSK-based signal structures have been used for global TWSTFT links among NMIs. The BPSK-based signal structure has the advantage of having a simple transceiver structure but is inappropriate for long coherent integration time in correlation processing. Also, BPSK-based ACF have relatively wide main lobe width and low sharpness waveform. Those ACF properties cause signal-tracking performance degradation. Conventional TWSTFT code sequence sets have relatively high cross-correlation power levels. Properties of those code sequence sets are inappropriate for service to multi-user simultaneously. In this paper, a BOC and Truncated M-sequence based new TWSTFT signal structure was proposed for improving those conventional signals. To evaluate the new TWSTFT signal structure and its code sequence sets, PSD, processing gain, ACFs, and cross-correlation power levels were compared with those of conventional SATRE, SRS modem, and GPS L1C/A, L1Cp signals.
An automated permuting capacitive device (PCD) was developed for the AC voltage ratio calibration of coaxial bridges. For user convenience and measurement accuracy, the permutation of the PCD capacitors was automated using a coaxial multiplexer. Our digital impedance bridge works at frequencies up to 100 kHz, and its voltage ratio needs to be precisely calibrated for impedance ratio measurements. The PCD can calibrate the 10:1 voltage ratio of the bridge for either the inductive voltage divider or the sinewave generators. The voltage ratio calibration using the PCD was studied and verified using reference values.
The uncertainty of instruments currently available for measuring magnetic moment is about 0.5%. To further improve the measurement accuracy of the magnetic moment for permanent magnets, a measurement system using compensated Helmholtz coils and a phase-locked method is developed. The coil constant of the Helmholtz coils is calibrated using null detection method. The uncertainty of the magnetic moment for the new method is 0.09%. The principle and results are discussed.
This paper presents a high-sensitivity micro-capacitance detection circuit designed for capacitive micro-displacement sensing. The circuit exploits the virtual short characteristic of the operational amplifier (op-amp) to achieve equipotential driven guard in triaxial cable, thereby mitigating the impact of cable parasitic capacitance. Additionally, the op-amp’s reference ground potential is allowed to float with the potential of the target capacitor, effectively overcoming the influence of parasitic capacitance to ground. Based on a self-developed three-terminal capacitive displacement sensor, it has been confirmed that the circuit possesses the capability to detect micro-capacitance variations at the zeptofarad (zF) level, thereby meeting the detection requirement for nanometer-level displacement resolution within the millimeter range.
A precision 30-MHz phase-shifting circuit has been experimentally constructed for accuracy testing and calibration of dual-channel RF attenuation and phase-shift measurement systems. The circuit is a re-routing circuit that can recombine RF input signals with the same amplitude but whose phase can be set arbitrarily, resulting in calculable RF attenuation and phase-shift values.
We have performed a detailed characterisation of a commercial small current source-measure unit (SMU), the Keithley 6430, by calibrating it against an accurate reference current source on current ranges from 1 nA to 1 mA. The instrument shows a marked non-linearity at small fractions of full-scale, but over a period of four years its gain factor is stable to better than 50 mu A/A on all ranges. This is sufficient for practical applications in metrology fields such as ionising radiation or photometry.
As power converters gain a pivotal role in driving the energy transition of power networks, new electrical phenomena are emerging in the grid. Amongst them, a new type of sub-synchronous oscillation has been identified as originating from the interaction of power converters connected to the grid. This paper discusses the detection and measurement of sub-synchronous oscillations along with the instrumentation requirements.
VSL has developed a new reference measuring system with rated voltage of 1200 kV for on-site calibration of lightning impulse voltage up to 3000 kV. The new measurement standard was compared with reference measuring systems from other national metrology institutes in a special comparison campaign. Based on the results of the campaign, calibration and measurement capabilities were realized in testing voltage (U-t), front time (T-1) and time-to-half value (T-2) with uncertainties of 0.7 %, 3.0 % and 1.5 % respectively up to 600 kV and 1.2 %, 5.0 % and 3.0 % respectively up to 1200 kV. Together with additional linearity experiments, VSL is now able to provide lightning impulse voltage calibrations up to 3000 kV on-site. This reference system has been used for the calibration and further tuning of a 4000 kV damped capacitive voltage divider from the Delft University of Technology to improve its voltage and time parameters measurement accuracy.
Specular gloss is the perception by an observer of the mirror-like appearance of a surface. The specular gloss value is determined from the ratio of the measured luminous reflectance of a specimen to the theoretical Fresnel reflectance of the standard. Luminous reflectance has been measured by an absolute technique using the SIMT primary glossmeter, and resulting gloss values have been calculated. The measurement results agree well with theoretical gloss values, which validates the method and accuracy of our instrument.
