Search

The total luminous flux is one of the most important characteristics of LEDs. The total luminous flux measurement of traditional LEDs with low power (0.05W@20mA), low heat and single package must conform to the specifications of CIE 127: 2007 Measurement of LEDs. Compared to traditional low-power LEDs, the latest LEDs have higher power (1W@350mA), higher heat and exhibit more complex packages. Because of their own characteristics, high-power LEDs have put forward some new measurement requirements for standard light source, heat dissipation structure, special fixture and integrating sphere. Therefore, a new type of 2π standard light source has been designed and used for the total luminous flux calibration of high-power LEDs.

UV LED has been widely used in various fields such as medical disinfection and biochemical detection, especially in UV curing. Compared with traditional high-voltage mercury lamp, UV LED shows large differences both in the spectral power distribution and irradiance, which may cause up to 20% error in calibration. A 365 nm UV LED source has been developed and measured, which is made of UV LEDs, temperature control module, integrating sphere, circuit and monitoring module. The experiment results indicate that the irradiance of about 884 mW/cm2 meets the actual requirements of the curing industry, and the stability of 1.0% (15 min) and uniformity of 1.6% are in compliance with the calibration regulation.

The Keysight 3458A is a common digitizer because of the great accuracy and small integration time. The bandwidth of its DC input path varies depending on the magnification of input amplifier of different ranges, which causes time latency of input signal. A method to measure the latency based on aperture time is introduced. When the aperture approximately equals to the period of the signal under test, extremum of sampling value reflects signal's initial phase. Experiments at 1V and 10V ranges with input signals of 25kHz and 50kHz were carried out and the time latency were measured. Then the bandwidth were calculated which were the same of about 120kHz for these two ranges.

A reference system for the calibration of electronic transformer tester based on the digital sampling method is described. The calibration software is designed in conformity to the IEC 61850-9-2/LE standard. The extended uncertainties estimation to the current function of the electronic transformer testers are 5.4E-5 for magnitude and 64prad for phase displacement with coverage factor k=2. Corresponding to the voltage function, the extended uncertainties are estimated to within 2.2E-5 and 50prad separately.

This paper describes the development of a 300-kV standard full lightening impulse measurement system. The high-voltage (HV) arm of the impulse resistive divider was constructed with an air-insulation frame wound with nichrome alloy resistance wire using the Ayrton-Perry winding method. The winding inductances of different frame cross-sectional shapes were studied. The result showed that the rectangular shape gives the least winding inductance compared with the circular and square cross sections under the condition of the same circumference. The HV arm was divided into 10 sections, and the stray parameters were subtracted with Finite Element Method method; the step response of the system is simulated with Simulink of MATLAB to optimize shield ring design. The low-voltage arm is composed of 24 low-inductance metal film resistors, which is similar in design to that developed by a Russian national metrology institute. The step response measurement result showed that the partial response time was less than 5 ns. The convolution method is used to evaluate uncertainty due to different waveform shapes based on the normalized step response. The expanded uncertainty evaluation of peak value gives 0.5% ( $k =2$ ), and the time parameter $T_{1}$ is 2.6% ( $k=2$ ) and $T_{2}$ is 1.3% ( $k =2$ ).

A kind of quasi-balance four-terminal ac resistance bridge has been constructed. The electronic inductive voltage divider provides high accurate voltage ratios for the bridge at a wide frequency range from 20 Hz to 10 kHz. The Wagner network with electronic circuit containing followers and amplifiers makes the voltage ratio unaffected by internal loading of ratio winding. Amplifiers are used to eliminate voltage drop on the lead wire connecting two resistors. Sampling method is used to measure the complex voltage ratio. The bridge can measure resistances from $1~\Omega $ to 1 $\text{M}\Omega $ . The optimal uncertainty for resistance of 100 $\Omega $ and 1 $\text{k}\Omega $ is $2\times 10^{-7}$ at 1 kHz.

Specular gloss is the perception by an observer of the mirror-like appearance of a surface. Specular gloss is usually measured by a glossmeter, which can be calibrated by a group of gloss plates according to JJG 696-2015. The characteristics of a gloss meter include stability, zero error, and error of indication. The characteristics of a gloss plate include roughness and spectral transmissivity of a high gloss plate, spectral reflectivity of a ceramic gloss plate. The experiment results indicate that calibration of both gloss meters and gloss plates should be carefully performed according to the latest verification regulation in order to reduce the measurement error.

Specular gloss is the perception by an observer of the mirror-like appearance of a surface. The measurement of specular gloss consists of comparing the luminous flux reflected from an object to that reflected from a gloss reference standard. The accuracy of specular gloss measurements depends not only on the characteristics of the instrument but also on the properties of the gloss reference standard. Experiments have been performed to analyze the possible sources of error such as gloss reference standard variation, photodetector linearity and measurement repeatability, which are three most important components of uncertainty. The results indicate that the instrument should be carefully examined before the specular gloss measurement in order to acquire a satisfied result.

Specular gloss has been widely used to characterize the ability of a surface to reflect light specularly. Specular gloss is theoretically related to the physical properties of a surface, such as roughness, directionality and uniformity. Specular gloss, mainly determined by incident angle and refractive index of a surface, is a relative measurement quantity. Specular gloss is usually measured by a glossmeter. The topographical and optical properties of a surface have been analyzed on how to affect the measurements. The experiment results indicate that a less rough/flatter, more isotropic and more uniform surface will result in a more accurate measurement value. Therefore, physical properties of a surface must be carefully inspected before the specular gloss measurement in order to acquire a satisfied result.

Dissipation factor of the capacitor can be measured precisely by capacitance bridge. A kind of transfer circuit containing the auxiliary balancing circuit is used to compare the four-terminal resistor and the standard capacitor. Voltages of the two kinds of impedance are sampled synchronously by a two-channel digitizer. The phase difference of the voltages is computed by improved DFT algorithm. Based on the dissipation factor of the standard capacitor, time constant of the resistor can be computed. Experiments show the uncertainty of 8 ns with this method.

Digital sampling method is widely used in precision electromagnetic measurements based on DFT algorithms. The accuracy of phase difference measured by sampling method influences a lot to power, energy and so on. The active phase shifter is constructed to get stable 90° phase standard. To obtain the error of the phase shifter, two calibration steps are carried out in which a 1:-1 two-stage inductive voltage divider (IVD) is used. The calibration uncertainty for the 90° phase difference is 0.0006°. With the 90° phase standard, phase difference measured by a synchronous sampling digitizer using an improved DFT algorithm is calibrated.

The calibration of electronic transformer (ET) with digital output can be realized using reference digital voltage multimeter(DVM)with synchronized sampling. However, there are time related errors of DVM which affect the result of phase displacement of ET under calibration. Such errors include the trigger latency, bandwidth limitation and aperture time of the DVM. This paper estimates the errors and makes a correction to the calibration result. The accuracy of the correction is verified using an arbitrary waveform generator (AWG) with dual synchronized channels with satisfactory results.

This paper describes a calibration system based on digital sampling of the reference synchronized to the pulse-per-second (PPS) signal of the merge unit (MU) for electronic transformer (ECT/EVT) under test. This calibration system is designed in conformity to the IEC61850-9-2LE standard for digital substation. The reference system included a two-stage CT up to 10 kA, a non-inductance shunt, reference VTs up to 220 kV/V3, an inductive voltage divider (IVD), a sampling voltage multimeter (DVM), a function generator(FG), a fiber-Ethernet converter and a clock synchronization device. Software for instrument control, packets capturing and a compensated discrete Fourier transform (DFT) algorithm were developed for the system. Uncertainty evaluation proved that this reference system is qualified for calibrating electronic transformers (ETs) with an accuracy class of 0.1S/0.1.

A set of cascaded IVDs with ratio of 2n:1 has been designed and self-calibrated. The IVD is built based on the use of the cascaded structure between the IVD with ratio of 2n-1:1 and BIVD. The amplitude errors and phase angle errors of the IVDs with ratios from 2:1 to 256:1 have been measured by means of sampling method at frequencies ranging from 10 kHz to 100 kHz, and the measurement results are presented.

A solar simulator is a device that provides illumination approximating natural sunlight. Solar simulators are classified as A, B or C for each of the three categories based on criteria of spectral distribution, irradiance non-uniformity on the test plane and temporal instability of irradiance. In this paper, we find that spectral match may change during the pulse of a pulsed solar simulator. In our experiments, a second PV device, which is placed at a fixed position outside the test area, has been used for monitoring the irradiance during the pulse and correcting the measurement results. We focus on the temporal instability measurements of pulsed solar simulators, especially for those whose irradiance changes rapidly during the time of data acquisition, and make a conclusion.

An apparatus for determining the spectral response of large area solar cells based on filter method has been introduced. The spectral response of a solar cell is measured by irradiating it by means of a narrow-bandwidth light source at a series of different wavelengths covering its response range, and measuring the short-circuit current density and irradiance at each of these wavelengths. Experiments have been performed to analyze the factors which can affect the spectral response measurements such as the full width at half maximum (FWHM) of filters, the non-uniformity of monochromatic light. The results indicate that less FWHM of filters, more uniformity of monochromatic light will lead to a more accurate measurement.