Question

A vibration measuring instrument has a bandwidth of 0-1kHz, and a sensitivity of 4 voits per imm/še, The pichupis useé on machinery whose frequensy can range from 10 Hz (idling) to 1 kHz (peak output.) If the acceleration is 1g the velocity pickup tend to emphasize low frequency or high frequency signals?

Answer 1

Vibration pickups are mostly linear in operating range.

Equation for Vibration Sensors:

Acceleration = Velocity * $\omega$

=$2*\pi*f*Velocity$

for 10Hz:

Voltage = 4V/(mm/sec) * ($f*2pi$)

= 4/1000*10*2*3.1416

= 0.251V

for 1KHz:

Voltage = 4V/(mm/sec) * ($f*2pi$)

= 4/1000*1000*2*3.1416

= 25.1V

Velocity pickups have very low natural frequencies and tend to pick low frequencies