Patent ID: 7368920
Filing Date: 2008-05-06
Classification: G01D,G01N,H04R

Abstract:
1. An electric potential fixing apparatus that is connected to a connection line between two capacitances, a first capacitance that is a measuring capacitance and a second capacitance that is directly connected to the first capacitance comprising: an output terminal that is connected to the connection line; a voltage supply unit operable to maintain constantly electric potential of the connection line between the two capacitances, holding combined total electric charge quantity of the first capacitance and the second capacitance by supplying voltage to the connection line from the output terminal; an alternating-current voltage generator which generates an alternating-current voltage; and a first operational amplifier having an input terminal connected to the connection line and another input terminal connected to the alternating-current voltage generator; wherein the voltage supply unit includes a first high resistance and a second high resistance that is directly connected to the first high resistance; a voltage dividing unit that outputs electric potential divided by the first high resistance and the second high resistance to the output terminal; and a third capacitance that is connected in parallel to at least either of the first high resistance and the second high resistance.