Resonance circuit used for measurement device and measurement device

A measurement device comprising:

• a detector configured to output an analog displacement signal based on displacement of an object occurred when the object is vibrated;
• a ΔΣ modulator configured to ΔΣ-modulate the analog displacement signal to output a pulse density signal;
• a low-pass filter configured to convert the pulse density signal to a multi-bit signal;
• and
• a resonance circuit configured to generate an excitation signal based on the pulse density signal and the multi-bit signal, the resonance circuit comprising:
• an amplification factor controller configured to set an amplification factor depending on a vibration signal obtained from the multi-bit signal;
• a multiplier configured to amplify a level of the pulse density signal by the amplification factor;
• and
• a circuit group configured to generate the excitation signal based on a pulse density signal obtained by further ΔΣ-modulating an output of the multiplier;
• wherein the amplification factor controller is configured to set the amplification factor using a proportional control and an integral control based a difference between an amplitude signal obtained from the vibration signal and a target amplitude value.