Sensing Device

A sensing device which uses a sensor resonator including a piezoelectric plate forming an adsorbing layer to adsorb an object to be detected on the surface thereof and changes the natural frequency thereof by adsorption of the object, and detects the object by variation of the natural frequency of the sensor resonator, comprising:

• a plurality of sensor resonators;
• a plurality of said oscillation circuits to oscillate a plurality of said sensor resonators respectively;
• a measuring unit provided for these plural oscillation circuits in common to measure the signal relating to the frequency of the oscillation circuit;
• a signal switchover unit to perform switchover connection of said plural oscillation circuits to said measuring unit in turn;
• a load switchover unit installed between each of said plural oscillation circuits and said signal switchover unit to switchover the load on the output side of each oscillation circuit between a first value and a second value in order to forcibly separate the respective oscillation frequencies of the oscillation circuits connected to said measuring unit from the oscillation circuits not connected to said measuring unit;
• and
• a switchover controller which outputs a control signal to said signal switchover unit so that each of said plural oscillation circuits is connected to said measuring unit in turn, and outputs a control signal to the load switchover unit so that the load on the output side of the oscillation circuit connected to the measuring unit is the first value and the load on the output side of the oscillation circuit selected from among the oscillation circuits not connected to the measuring unit is the second value.