Question

Determine the bandwidth for a seismic instrument employed as an accelerometer having a seismic mass of 0.2 g and a spring constant of 20,000 N/m, with very low damping. Discuss the advantages of a high natural frequency and a low damping ratio. Piezoelectric sensors are well suited for the construction of accelerometers, since they possess these characteristics

Answer 1

Cal culate the value of natural frequency k Here, k is the spring constant and m is the mass 20000 N/m -100 x 10° = 10,000 rad/s 0.0002 kg 20000 N/m2 0.2 g Consi der that the device is having very low damping The bandwidth can be found from the second-order system frequency response. It is in the frequency range 0 to 0.40 0.4 0.4(10000) = 4000 rad/s Therefore, the bandwidth of the seismic instrument is from 0 to 4000 rad/s The advantage of having high natural frequency is that it enables the sensor to measure extremely high frequencies very accurately. This makes the sensor capable to measure unusual vibration and disturbances The advantage of having low damping ratio is that the phase shift is linear with the frequency and therefore as a result the distortion becomes less