| 摘要 |
PROBLEM TO BE SOLVED: To provide a sensor device capable of providing a wide dynamic range without cost increase even with a low voltage of a source and an electrophotographing device using it. SOLUTION: A potential sensor 10 includes a piezoelectric tuning fork 11 as a mechanical vibration means. The piezoelectric tuning fork 11 includes a vibration body 11a of a tuning fork type. A driving piezoelectric element 11b for driving the vibration body 11a is provided on one arm portion of the vibration body 11a and a returning piezoelectric element 11c for returning a signal to the driving piezoelectric element 11b is provided on the other arm portion of the vibration body 11a. A detecting electrode 12 is formed on a surface of the other arm portion of the piezoelectric tuning fork 11 and the piezoelectric tuning fork 11 is disposed such that the detecting electrode 12 is opposed to an object to be measured 13. A circuit block of the potential sensor 10 is approximately constituted by a self-excitation oscillation circuit 14 for self-excitation driving the piezoelectric tuning fork 11; a signal processing circuit 20 for processing and detecting an electric signal obtained from the piezoelectric tuning fork 11; and a charge pump portion 30 accumulating a voltage by a periodical signal of the self-excitation oscillation circuit 14 and inputting the voltage accumulated in the signal processing circuit of. |
