| 摘要 |
<p>PURPOSE:To remove the attenuation of voltage induced in a sensing coil and to improve SN ratio by setting up the potential of a common line to ground potential to reduce the influence of electrostatic capacity of a switch group. CONSTITUTION:The common line 5 is connected to the inverted input terminal 29 of an amplifier 28 having a sufficiently high amplification factor and its non- inversion input terminal 30 is earthed. Since the potential of the inverted input terminal 29 is equal (imaginal short) to that of the non-inversion input terminal 30, and the terminal 30 is set up to the ground potential, the potential of the common line 5 is the ground potential. Therefore, said state is equivalent to the state that both the ends of the equivalent electrostatic capacity of the switch groups 3, 4 are earthed, and the induced voltages of the sensing coil groups 1, 2 are prevented from attenuation due to the electrostatic capacity.</p> |
