Commercial capacitance bridges are used as accurate transfer standards in the calibration of fused-silica capacitors. Tedious manual bridge measurements are still the basis for transferring the unit of capacitance from the calculable capacitor, which realizes the farad, to the U.S. representation of the farad, which is a bank of 10 pF fused-silica… (More)
—We describe dissipation factor measurements of 10 pF fused-silica capacitance standards from 50 Hz to 20 kHz, using a toroidal cross capacitor and a 10 pF nitrogen-filled capacitor as the references. The relative combined standard uncertainties are 0.56×10-6 , 0.16×10-6 , and 0.26×10-6 at 100 Hz, 1 kHz, and 10 kHz, respectively.
We established a red callus from the leaves of a red-fleshed apple individual, which was a hybrid offspring of the cross between Malus sieversii f. niedzwetzkyana and Malus domestica cv. ‘Fuji’. We analyzed callus growth and anthocyanin biosynthesis/metabolism under different combinations of temperature and light conditions. Incubation in darkness resulted… (More)
In response to a growing demand for loss measurements for standard capacitors, staff members in the Quantum Electrical Metrology Division at the National Institute of Standards and Technology (NIST) are working to develop a calibration service for dissipation factor. The demand is driven by increased use of commercial automatic capacitance bridges in the… (More)
— We describe dissipation factor measurements of 1 pF, 10 pF, and 100 pF fused-silica capaci-tance standards from 50 Hz to 20 kHz, using a toroidal cross capacitor and a 10 pF nitrogen-filled capacitor as the references. We also describe an analytical model that relates the dissipation factor of a capacitor to the frequency dependence of its capacitance.
AC bridge techniques commonly used for precision impedance measurements have been adapted to develop an eddy current sensor for rail defect detection. By using two detection coils instead of just one as in a conventional sensor, we can balance out the large baseline signals corresponding to a normal rail. We have significantly enhanced the detection… (More)