Some embodiments relate to a vibration sensor. The vibration sensor comprises: a sensor base to couple to a vibration source; a piezoelectric transducer coupled on a first side of the transducer to the sensor base; at least one conductor coupled to the piezoelectric transducer; and a seismic weight positioned on a second side of the piezoelectric transducer; wherein the sensor base, the piezoelectric transducer and the seismic weight are aligned along an axis and arranged so that relative movement between the sensor base and the seismic weight arising from the vibration source causes a current to be generated in the piezoelectric transducer and an output signal corresponding to the generated current is detectable on the at least one conductor.