| 摘要 |
<p>TECHNIQUE AND APPARATUS FOR MEASURING THE VALUE OF A CAPACITANCE IN AN ELECTRICAL CIRCUIT SUCH AS A TELEPHONE COMMUNICATION LINE BSTRACT OF THE DISCLOSURE A technique for measuring the value of a capacitance that is inseparatably connected with other circuit elements as part of a composite electrical circuit. The measurement is insensitive to such other elements that include resistances, inductances and active voltage sources. The technique involves the charging of the unknown capacitance followed by an immediate transfer of that charge to an external known capacitance that is part of an integrating circuit. The voltage stored by the known capacitance is unaffected by series resistances and is proportional to the desired electrical circuit capacitance being measured. The effect of induced or generated interfering signals in the circuit are cancelled by transferring the charge to the known capacitor for a period equal to an integral multiple of periods of the interfering signal. Furthermore, the charging voltage is adapted to the particular circuit in order to compensate for any resistance shunting the capacitance being measured. These techniques have a particular application to capacitive measurements of telephone communication lines.</p> |
