1,721,012 research outputs found
Groove depth measurements on roughness reference standards of the Croatian National Laboratory for Length (LFSB)
No full textA method for linearization of a laser interferometer down to the picometre level with a capacitive sensor
No full textThis paper describes methods for dynamic measurement and correction of laser interferometer periodic nonlinearity down to the picometre level. A capacitive sensor is used as an external reference for measuring and calculating the periodic interferometer nonlinearity correction function. The experimental interferometer setup is a heterodyne interferometer with symmetrical paths to detectors and time-interval-based phase detection. The periodic nonlinearity is represented as harmonic Fourier components. The time evolution of the nonlinearity function is tracked during measurement. The method is verified by spatial and temporal repeatability of the measured nonlinearity. Linearization repeatability in the 10 pm range is observed
Final report on EUROMET.L-K4: Calibration of diameter standards, Group 1
No full textKEY COMPARISON
At its meeting in October 2003, the EUROMET (now EURAMET) Technical Committee for Length, TC-L, decided upon a key comparison on diameter standards. Due to the large number of participants, it was decided to have two groups arranged according to the claimed uncertainties. Eleven laboratories from EURAMET and two laboratories from other RMOs participated in the group 1. The circulation of the gauges started in June 2005. The comparison was registered as EUROMET project 812.
The final report for the group 1 describes the results of measurements of five diameter standards (one sphere, two rings and two plugs). A third plug was added for optional measurements. The main measurand was the diameter of each gauge at 20 oC and corrected to zero force. The diameter was measured at three heights of each cylindrical gauge. As requested by the protocol, laboratories also provided the departure from roundness of the sphere. Participants were invited also to report the roundness and the straightness of the cylindrical gauges.
The reference values were calculated from the weighted mean of the larger consistent subset of results according to the Birge ratio criteria. In general, the overall agreement was good, with some larger spread of results for the plugs
A novel AC current source for capacitance-based displacement measurements
No full textA 100 kHz bandwidth ac current source suitable to be used with capacitive sensors in displacement measurement applications has been designed and constructed, The high-output impedance of the source is obtained by sensing the load voltage with a buffer stage having very low input capacitance, The sensing-buffer power supply, its shield, and the input shielding connections are driven at the buffer input potential in such a way that the effect of all input parasitic admittances, including the buffer common-mode impedance, are almost suppressed. The load impedance variations. which are directly proportional to displacements, are monitored by the output voltage of the sensing buffer, Measurements made at different frequencies with calibrated capacitance loads ranging from (1 to 20) pF have shown that the load-impedance values are proportional to the output voltage of the sensing buffer with a linearity better than 4 x 10(-4) and resolution of about 3 x 10(-5) over a 1 kHz bandwidth of load variation signal, The features of the current source and its performance in a displacement measurement application are described
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