Capacitance Sensor

A capacitance sensor comprising:

• a package;
• an oscillation circuit provided inside the package;
• a switch circuit provided inside the package;
• a first reference capacitor provided inside the package;
• and
• a first electrode and a second electrode provided outside the package, wherein
• the oscillation circuit includes
• an amplifier, and
• a resonator provided inside the package and connected between an input node and an output node of the amplifier,
• the first electrode is an electrode for sensing,
• the second electrode is an electrode having a fixed potential,
• the switch circuit switches between connecting the first electrode to and connecting one end of the first reference capacitor to a first node which is one of the input node and the output node of the amplifier, and
• an oscillation frequency of the oscillation circuit changes according to a first capacitance between the first electrode and the second electrode when the first electrode is connected to the first node.