Abstract: Longitudinal piezoelectric constant is one of the key parameters of piezoelectric materials. The quasi-static method is most widely used to measure this constant. There are often differences in measurement results obtained using commercial instruments. A quasi-static measurement system was established with a dynamic force sensor, traceable to the primary standard. Factors affecting measurement were systematically studied, including the pretension force, the dynamic force, and the electrode shape. In order to obtain stable measurement results of the piezoelectric constant, the static force should be more than 10 N and the dynamic force no less than 0.1 N. Relatively more accurate measurement results of the piezoelectric constant were obtained using an electrode with a smaller spherical radius to clamp the piezoelectric material. Calibration of commercial longitudinal piezoelectric measuring instruments is discussed. The parameters to be calibrated should include the dynamic force, the static force, and the measurement error.
Abstract: Techniques for measuring sound pressure levels using the PULSE system are studied. Based on the definitions of microphone sensitivity and the open-circuit sound pressure sensitivity level, varying the sensitivity levels of the PULSE system obtained different sound pressure levels in the experiment. Then the open-circuit sound pressure sensitivity level of the microphone was corrected for to make the measured sound pressure level more accurate.
Abstract: A measurement system for bone conduction headphone acoustic parameters was designed to explore the advantages and potential applications of new bone conduction headphones in audiology tests. The maximum output intensity and harmonic distortion of two commonly used bone conduction headphones, i.e. B-71 and B-81, were compared at five listening frequencies. At the same maximum output intensity, the harmonic distortion of B-81 headphones at four frequencies in the range 250 Hz to 2 000 Hz was significantly lower than that of B-71, and no significant difference in the harmonic distortion of B-71 and B-81 headphones was observed at 4 000 Hz. B-81 headphones were better than B-71 headphones in terms of both the maximum output intensity and the harmonic distortion, especially in the low and middle frequency bands. The test results show that B-81 can be used instead of B-71 in audiology-related tests.
Abstract: An automatic verification system for octave-band and fractional octave-band filters based on LabVIEW was designed to improve the efficiency and accuracy of verification. The system uses a computer as the core controller and employs the virtual instrumentation technology. By using standard interfaces to connect the instruments that need remote control, a reference signal source and the parts under measurement are integrated into a single system. Following the verification regulation, the system realizes automatic control of instruments, automatic reading of response data, data analysis and processing, and generation of raw data report, etc. Multiple tests show that the system is stable and reliable and lends itself to improving efficiency and accuracy and avoiding human errors.
Abstract: The advantages of the direct measurement method for absorbed dose to water in Report TRS-398 were studied. This is a promising method for determining prescription dose in clinical applications and reducing the uncertainty of clinical radiotherapy dosimetry. By introducing the conditions and methods for directly measuring the absorbed dose to water under different kinds of radiation, part of the experimental data based on TRS-398 report measurement method is summarized. The results show that the repeatability of the direct measurement method is less than 0.5% and the uncertainty of dose measurement is less than 2%. The direct measurement method for absorbed dose to water meets the uncertainty requirement of clinical dose outputs, i.e. less than 5% (k=1). These results provide a theoretical basis for updating the method of dose output measurement in clinical radiotherapy.
Abstract: A highly stable white field instrument for LED-backlit liquid crystal displays was developed. It has functions of luminance monitoring, luminance calibration and luminance compensation. This instrument can be used for laboratory and field calibration of color analyzers and periodic verification of luminance colorimeters. Its metrological characteristics, including luminance, chromaticity, spectrum, stability and uniformity, were studied. The uncertainty in calibration of color analyzers with the white field instrument was evaluated.
Abstract: Nonlinearity is the main characteristic of thermoelectric laser power detectors, which represents the change in the detector response under different power, and has an important impact on the measurement accuracy. Based on the electrical substitution method, this paper studies the measurement method for response nonlinearity of laser power detectors at several watts to several hundred watts. An electrical calibration device was developed that can automatically measure electrical calibration responsivity under different power levels. Different from the common constant-voltage mode or constant-current mode, the device has a constant-power output mode, which can significantly improve the stability of loading power for electric calibration heaters with a large temperature coefficient. In the study, two electrical calibration laser power detectors were fabricated based on two kinds of ceramic heaters, and the response nonlinearity of the electrical calibration was measured. The results showed that for the MCH ceramic heater with a large temperature coefficient, the loading power instability under the constant-power mode was 0.025%, which is much lower than 2.0%, i.e. the instability under the constant-voltage mode. Due to the higher power stability and the automated measurement process, the evaluated uncertainty of the measured electric calibration responsivity was better than 0.10% in the power range 0.49 W to 189 W, which was an improvement on the accuracy of the nonlinearity measurement of electrical calibration.
Abstract: This paper studies the atmospheric distillation method based on the method in the national standard GB/T 6536-2010, with the focus on the traceability of the recovered temperature. The consistency between the measured recovered temperatures by a platinum resistance and by a mercury thermometer was achieved. We collaborated with several laboratories to certify the CRM developed. The uncertainty of the certified values Uc (k=2) from the initial boiling temperature to 95% of the recovered temperature ranged from 0.7 ℃ to 4.6 ℃.
Abstract: Vertical metal tanks (hereinafter referred to as vertical tanks) are a measurement instrument that requires compulsory verification. The measurement accuracy directly relates to trading parties’ economic interests. This paper discusses factors affecting accuracy of volume measurements of vertical metal tanks, including the incident angle’s effect (no more than 60°) in total station surveying, the correlation between inputs in uncertainty evaluation for radial deviation measurements, the strapping method for measuring the base circle, and dealing with the outliers when fitting the measurement center and radius.
Abstract: Skin friction is a major part of the total resistance an object encounters when moving in a fluid. Due to the difficulty in theoretical analysis and the diversity of flow fields, direct measurement of skin friction is needed in various applications. This paper introduces a design of elastic body for strain-type skin friction sensors. A mechanical analysis of the sensor was carried out. The analysis showed that the radius of the sensor’s hole, the spacing between the parallel beams, and the thickness of the connecting beam are the main parameters affect ing the performance. Then representative combinations of the parameters were selected using the orthogonal experimental method. The strain distribution in the patch area was calculated by using FEM. New parameters were defined to coordinate conflicting optimization goals. The influence of each parameter was analyzed to determine an optimal combination.
Abstract: In the daily use of large weighing mass comparator, there are often large data fluctuation, reduced accuracy and easy damage of sensor. It is found that during the use of the mass comparator, the application of the corresponding weight lifting method will have a great impact on the use of the mass comparator. In the traditional lifting method, the weight will have a great impact on the table of the mass comparator, which is the main reason for the poor use effect of the mass comparator. In order to solve the above problems, an auxiliary device of mass comparator is designed, and its application effect is analyzed. It is found that the application of the device can greatly improve the repeatability of weighing, reduce the measurement error caused by eccentric load, reduce the data drift and improve the accuracy.
Abstract: In view of the revision of the verification regulation for infrared thermometers, including infrared ear thermometers and infrared forehead thermometers, and the enormous demand for testing during the epidemic, a integrated test device with three tanks for infrared thermometers was developed. A dark channel was used to increase the liquid circulation rate of thermostatic bath, and a screw cap was used to make the blackbody cavity easy to disassemble for storage. A touchscreen controller was used to control the temperature of the three tanks simultaneously through RS-485, with additional functions such as one-key control and correction provided. The overall testing of the device showed that the device has good temperature stability and temperature field uniformity and high accuracy of brightness temperature, and can greatly improve testing efficiency.
Abstract: This paper proposes a separable probe for combustible gas detection in order to decrease the risk of high-altitude operation.In this design, the probe is divided into two parts, i.e. one fixed part and one removable part. The fixed part includes an explosion-proof junction box and an electromagnet terminal in the box. The removable part is the main part of the probe, which can be removed for calibration and adjustment. The two parts are attached to one another by the electromagnet. When the probe needs verification or maintenance, the electromagnet is turned off by remote control, so that the removable part can be taken off. The explosion-proof type, structure size, structure strength of the explosion-proof junction box, and electromagnet selection are analyzed in detail.
Abstract: Using qualitative and quantitative analyses, the differential scanning caloric (DSC) method for determining purity of DMT is introduced, with uncertainty evaluated. A measurement comparison with the mass balance (MB) method validated the results of the DSC method. The chemical composition of a DMT sample was determined by gas chromatography with tandem mass spectrometry and a fourier transform infrared spectrometer. The certified value was studied by the DSC method.
Abstract: The influence of detrimental intermetallic phase in duplex steels on their toughness and corrosion resistance can be detected by the ASTM A923-2014 standard ferric chloride corrosion test method, with the value characterized by corrosion rate. This paper analyzes the uncertainties due to the weight, length, width and thickness of the samples before and after the corrosion. The uncertainty components were calculated and then combined to obtain the expanded uncertainty. Taking into account the expanded uncertainty and other factors, the upper limit of the acceptance criteria for the test method was chosen. In order to eliminate the detrimental intermetallic phase and finally improve the product quality, proper heat treatment is needed on the samples exceeding the upper limit. The results showed that the detrimental intermetallic phase of 2205 duplex stainless steel was (3.9±1.4) mg/(dm2·d), with a coverage factor k=2. The upper limit of the acceptance criteria for this test method was chosen to be 8 mg/(dm2·d).