| Popis: |
In high-permeability materials, the voltage waveforms induced in a search coil are pulse-like. To determine the sampling conditions for a digital dc fluxmeter, the accuracy of digital integration in such cases has been examined. The accuracy was estimated by means of computer simulations using the following pulse-like waveforms: they are rectangular, triangular and half-sinusoidal ones which were idealized actual voltage waveforms. It was found that there is an essential difference in errors between the trapezoidal approximation and the simple accumulation. To investigate this fact, the effect of sampling number on the integration accuracy was discussed from a general consideration using the Fourier series expansion. The accuracy is rapidly increased with the number of sampling data per cycle and then the rate of the improvement becomes very slow. In the trapezoidal approximation there are only amplitude errors, while in the simple accumulation there are phase errors in addition to amplitude errors. The phase errors have a large influence on the accuracy. A new corrected method which is combined with the shift of a half sampling period has been proposed as an adequate measure. |
