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The dc high voltage is usually measured with high-voltage divider which plays the role of the ratio standard linking the unknown high voltage to the well-known low-voltage standards. A step-up method had been proposed to calibrate the dividing ratios of the high-voltage dividers at nominal test voltage. The step-up technique has been newly modified for improving the transfer accuracy of reference values determined in voltage stack stage, with employing an additional source voltage monitoring device, and successfully applied to precisely determine the dividing ratios up to 100 kV. Typical standard uncertainty for the dividing ratios is estimated to be approximately $5 \times 10^{{ {-6}}}$ .

We have fabricated a single-stage superconducting quantum interference device (SQUID) current amplifier for detecting pulse outputs of a superconducting microcalorimeter. The current amplifier is made of a double relaxation oscillation SQUID (DROS) that provides a high flux-to-voltage transfer of about 1mV//spl Phi//sub 0/ and a large modulation depth of 80 /spl mu/V. Due to the high flux-to-voltage transfer, the voltage output of the DROS is measured directly with a room-temperature dc preamplifier. The bandwidth of the current amplifier is measured to be 1.2 MHz. Typical noise of the DROS current amplifier is about 6 pA//spl radic/Hz.

Nonhysteretic Josephson junctions array of a very good uniformity is required for realization of programmable Josephson voltage standard. The tolerable nonuniformity of junction critical current in the presence of a Gaussian noise is analyzed with an accuracy requirement of PJVS.

A calibration technique of 1 0 based on a QfR standard(i4 step) using a commercial DCC bridge have been described. Sample characterizations and bridge ratios have been measured using the DCC bridge without a CCC bridge and total combined uncertainty is estimated as about O.lxlOd level.

A binary step-up method to determine the voltage coefficient of high dc voltage resistor has been developed. Range of voltage and accuracy of measurement depends only on stabilities of the high voltage source and the resistor under measurement. Rough measurement of 100 M/spl Omega/ resistor shows an uncertainty less than 100 /spl Omega//kV up to 50 kV.

We made a clock comparison system using the 10 kHz and 1 pps signal. A frequency divider is used for generating 10 kHz signal from the clocks. Clock comparison is carried out by using the system from MJD 51160 to MJD 51196. We compared the results using the 10 kHz data with those using 1 second data averaged for 10 seconds. The precision of clock comparison was improved by using the clock comparison system.

The second harmonic of the 794 nm output of a GaAlAs diode laser is generated in a LiIO3 crystal in an external ring enhancement cavity. The dependence of the second-harmonic power on the input power has been measured and compared with the theory. The second-harmonic power of 7.4 µ W at 397 nm has been obtained with an input fundamental power of 28 mW by using an 8-mm-long LiIO3 crystal.

Photoacoustic measurements for polycrystalline samples of orthorhombic YBa2Cu3O7−x, GdBa2Cu3O7−x, and DyBa2Cu3O7−x have been carried out in the range of temperatures between 85 and 100 K. An anomalous change of photoacoustic signal due to the specific heat anomaly of the superconductor at transition temperature has been observed. The temperature at which the photoacoustic signal intensity changes anomalously has been found to correspond to the offset temperature of superconducting transition in resistivity measurement. The changes of photoacoustic signal have been analyzed using Rosencwaig and Gersho’s theory [J. Appl. Phys. 47, 64 (1976)]. The superconducting transition of the samples was, from the photoacoustic measurements, found to be a second‐order transition with no latent heat.

Measurement of time varying frequency is very important in many fields: acoustics, radar signal analysis, seismology, and power quality analysis. In this paper a comparison of several methods for frequency measuring will be performed. The methods were adopted for power quality frequency measuring according to the European standard EN 50160 “Voltage characteristics of electricity supplied by public distribution systems” [1]. The main idea was to measure frequency with as lower as possible sampling time, while trying to observe transients in frequency. The following methods were used for comparison: Interpolated DFT [2], Sine fitting [3], Chirp z-Transform [4] and Hilbert transform [5]. All signals were simulated as thou they are acquired with 16 bit A/D conversion, 50 kS/s, and with range of ± 10 V. The comparison will be in next step repeated on FPGA module with real measurement data.

This paper describes the comparison of the precise digital voltmeters and DAQ cards in measurement of resistance ratios. Recently, 24 bit DAQ cards have emerged as possible measuring instruments that can be used to develop precise measurement methods. They are not as expensive as digital voltmeters, and could replace digital voltmeters in many applications.