| 摘要 |
PURPOSE:To eliminate the noise of both of 50Hz and 60Hz commercial frequencies without sacrifice of the A/D conversion time neither switching by a switch or the like, by applying an input voltage to an integrator through a notch filter and setting the input voltage integrating time of the integrator to 20ms. CONSTITUTION:A voltage selected by scanner SC is inputted to a TWIN-T type notch filter NF. An integrating time Tx of the input voltage impressed through the notch filter NF and a preamplifier OA1 is set to 20ms for the purpose of eliminating the noise of 50Hz components especially. Though a back integrating time Ts is varied in accordance with the magnitude of an input voltage Ex, the time required for A/D conversion of the input voltage Ex is 40ms if a maximum value is taken approximately equally to the time Tx. Meanwhile, in the notch filter NF for eliminating the noise of 60Hz components, a notch eliminating frequency f0 is set to 60Hz. |
