Glossary

Frequency range (Dynamics)

Symbol

f

Unit

Hz

Because of their mechanical quality, piezoelectric sensors have very low damping. The useful frequency range is limited in the upwards direction by the increasing resonance rise.

Symbol:

• f        =      measuring frequency
• f_n      =      natural frequency
• A/A₀  =      amplitude ratio

The following approximate values apply to the amplitude error or achievable accuracy as a function of frequency:

• accuracy 10 %  ®     f_max » 0,3 · f_n
• accuracy   5 %  ®     f_max » 0,2 · f_n
• accuracy   1 %  ®     f_max » 0,1 · f_n

Schematic presentation of frequency response and phase response

Note: In their dynamic behaviour, piezoelectric sensors are superior to all other measuring methods. Their high rigidity results in the highest possible natural frequencies. Piezoelectric sensors are thus ideal for measuring measurands which change rapidly over time. Their dynamic behaviour is thereby largely determined by the surrounding structure. Therefore the frequency response of the entire measuring arrangement must be investigated for the largest possible, useful measuring range.

There are two possibilities here: frequency analysis, f.e. pressure sensors in shock tube or finite-element method.