DEFINITION | Bandwidth

Bandwidth, also referred to as Frequency Response, is an indication of a displacement sensor’s ability to respond to changes in the measured displacement. It is measured at the -3dB point and gives indication of:

  • How the output changes relative to the frequency of a vibrating target
  • Frequencies that can be captured and presented in the output when measuring a target in motion

It is NOT about digital information such as sampling rates or transmission speeds.

Sensor bandwidths usually only state the upper frequency limit and assume that the sensor works at DC (0 Hz) levels

What Happens At The Specified Frequency (-3dB)?

Bandwidth Specification is the -3dB Point

15 kHz Bandwidth Curve

 

It is critical to undertand that the stated bandwidth of a sensor is the frequency at which the output voltage is reduced to 70.7% of the lower frequencies (or DC) output levels. This means that a target vibrating with a displacement of 100 µm will only be measured as 70.7 µm when vibrating at the sensors bandwidth specification frequency.