Dual-frequency vibration sensor

A vibration sensor for sensing vibrations of the body of a vehicle, comprising:

• a disk-shaped metal plate secured to said body, said metal plate being capable of resonating at a first resonant frequency among the frequencies at which said body can vibrate, said first resonant frequency ranging from 100 to 700 Hz and;
• a vibration element comprising a shaft secured to said body, a support swingably joined to said shaft, a weight provided on said support, and a plate spring having an end fixed to a reverse surface portion of said support, said vibration element being capable of resonating at a second resonant frequency among the frequencies at which said body can vibrate, said second resonant frequency being not more than 10 Hz;
• and
• a piezoelectric transducer element fixed to a central portion of said metal plate and connected to the other end of said plate spring, said piezoelectric transducer element being capable of generating an electrical signal in response to the stress applied when said metal plate and said vibration element vibrate.

A vibration sensor for sensing vibrations of the body of a vehicle, comprising:

• a disk-shaped metal plate capable of resonating at a first resonant frequency among the frequencies at which said body can vibrate, said first resonant frequency ranging from 100 to 700 Hz;
• a piezoelectric transducer element fixed to a central portion of said metal plate, said piezoelectric transducer element being capable of generating an electrical signal in response to the stress applied by said metal plate when said metal plate vibrates;
• and
• a vibration element comprising a coilspring having an end fixed to said piezoelectric transducer element, and a weight fixed to the other end of said coil spring, said vibration element being capable of resonating at a second resonant frequency among the frequencies at which said body can vibrate, said second resonant frequency being not more than 10 Hz, said vibration element transmitting vibration thereon to said piezoelectric transducer element to generate an electrical signal.