Displacement, velocity and acceleration sensors.
There are three primary types of motion characteristics detected by vibration transducers normally referred to as accelerometers. These are
• velocity, and
The choice between these three different types of motion transducers depends on the frequencies that have to be measured and the levels of the signal involved. (Wilcoxon Research / ND)
Displacement sensors are normally used for low frequency (1 to 100 Hz) measurements and are useful for measuring very low amplitude displacements. They are employed in such applications as shaft motion and clearance measurements. Traditionally displacement transducers have employed non-contacting proximity sensors and eddy probes. Piezoelectric displacement transducers have recently been developed to overcome some of the mounting problems associated with non-contacting probes. (Wilcoxon Research / ND)
Velocity sensors are used for medium to low frequency (1 to 1000 Hz) measurements. Because they filter out high frequency signals, they are less susceptible to amplifier overloads which come from white background noise and which can compromise the fidelity of low amplitude and low frequency signals. Velocity transducers are useful for monitoring and balancing operations on rotating machinery. Velocity sensors normally employ an electromagnetic sensor to pick up the velocity signal. Now piezoelectric velocity sensors are becoming more popular. (Wilcoxon Research / ND)
Piezoelectric acceleration transducers are used to measure acceleration are the most commonly used motion sensors for vibration monitoring applications. They are useful over a wide band of frequencies from very low to very high frequencies (1 to 20,000 Hz) and are available in a wide variety of application specific designs. Piezoelectric accelerometers are the present most important tools used for vibration monitoring systems. (Wilcoxon Research / ND)
Why piezoelectric sensors?
Piezoelectric sensors are the best motion transducers presently available and are nowadays used for most industrial applications. They are rugged and of solid state construction and this enables them to operate under the most severe operating conditions. They are unaffected by dirt, oil, and most chemical atmospheres. They can also be used over a wide range of temperatures and resist damage from severe shocks and vibrations. There is no alternative to Piezoelectric accelerometers when considering their frequency range. They are highly accurate from very low to very high levels of motion signal amplitudes. Associated with microelectronic technology, piezoelectric transducers can be internally amplified as well as to include for a power battery and wifi transmitters for wireless communication. The other wired type of Piezoelectric transducers require a power supply and amplification equipment as well as a human interface readout equipment to be able to interface them to other analytical...