Patent ID: 8454902

Claim:
A sensing device using a piezoelectric vibrator whose characteristic vibration number changes by absorption of a substance to be sensed contained in a sample solution and sensing the substance to be sensed by a change of the characteristic vibration number, the sensing device comprising: a first piezoelectric vibrator configured to be provided with a first one-surface-side excitation electrode on one of a front surface and a rear surface of a first vibration area provided in a piezoelectric piece and a first other-surface-side excitation electrode on the other, respectively, and configured that the substance to be sensed is absorbed; a second piezoelectric vibrator configured to be provided with a second one-surface-side excitation electrode on one of a front surface and a rear surface of a second vibration area provided in the piezoelectric piece and a second other-surface-side excitation electrode on the other, respectively, and configured that the substance to be sensed is not absorbed; a switching part switching the first one-surface-side excitation electrode and the second one-surface-side excitation electrode each other to connect to a subsequent stage side; an oscillation circuit common to said first piezoelectric vibrator and said second piezoelectric vibrator, the oscillation circuit connected to the first other-surface-side excitation electrode and the second other-surface-side excitation electrode and provided in a subsequent stage of said switching part, and making said first piezoelectric vibrator and said second piezoelectric vibrator oscillate time-dividedly; and a measuring part provided in a subsequent stage of said oscillation circuit, and taking in outputs from said first piezoelectric vibrator and said second piezoelectric vibrator and measuring the characteristic vibration numbers of said first piezoelectric vibrator and said second piezoelectric vibrator, respectively, wherein an impedance of a conductive path including the first one-surface-side excitation electrode and an impedance of a conductive path including the second one-surface-side excitation electrode, when viewed from said oscillation circuit toward the first one-surface-side excitation electrode and the second one-surface-side excitation electrode, respectively, are uniform with each other, and wherein an impedance of a conductive path including the first other-surface-side excitation electrode and an impedance of a conductive path including the second other-surface-side excitation electrode, when viewed from said oscillation circuit toward the first other-surface-side excitation electrode and the second other-surface-side excitation electrode, respectively, are uniform with each other.