Piezoelectric Accelerometer

Piezoelectric Accelerometer

Question: Describe the principle of operation of a piezoelectric accelerometer. Discuss the factors that limit the frequencies over which vibration measurements can reliably be made.

Introduction

Piezoelectric accelerometers are without a doubt, the most superior motion transducers on hand for majority of the industrial applications. Their solid state, rugged construction facilitates them in operating and functioning in conditions that the most severe for a sensor to operate in. The piezoelectric accelerometers are not affected by majority of the chemical atmospheres, including oil and dirt.

Furthermore, they are also able to operate over an extensive range of temperature, and they have a resistance to being damaged because of extreme vibrations and rigorous shocks. The piezoelectric accelerometers are supreme and have no match for their range of frequencies and also, they are exceedingly precise and accurate from very high to very low levels of motion amplitude (Manfred, 2012). The Piezoelectric accelerometers are internally amplified and only require readout equipment and a power supply for the purpose of operation.

Principle of Operation of Piezoelectric Accelerometer

The active component of a piezoelectric accelerometer is a piezoelectric material. The figure given below (figure 1) demonstrates the piezoelectric effect by employing the assistance of a compression disk. A compression disk, in appearance, is just like a capacitor, having the piezoelectric material flanked by a couple of electrodes (Guy & Jeff, 2004). A force which is exerted at a 90 degree angle to the compression disk results in the production of voltage and charge at the electrodes.

Figure 1: Piezoelectric effect, basic calculations

The sensing component of the piezoelectric accelerometer is composed of two main parts;

Seismic mass

Piezoceramic mass

One end of the piezoelectric material is attached at the base of the sensor to a stiff post. The so called seismic mass is connected to the opposite end. At the instance when the piezoelectric accelerometer is exposed to vibration, a force is produced that acts upon the piezoelectric element (take a look at the figure shown below, i.e., figure 2).

In accordance with the laws of Newton, the product of seismic mass and acceleration comes out to be equal to this force. Due to this piezoelectric effect taking place, an output charge is generated that is proportional to the force exerted. Due to the reason that there is a constant seismic mass, the acceleration of the mass appears to be proportional to the signal of the output charge.

Figure 2: Principle of a Piezoelectric Accelerometer

The seismic mass, as well as the sensor base, over an extensive range of frequency, have a similar magnitude of acceleration. For this reason, the sensor notes the measurement of acceleration of the object under consideration. The piezoelectric component is attached to the socket of the sensor by means of a couple of electrodes. Many piezoelectric accelerometers have as their characteristic, an incorporated electronic circuit that transforms the charge output having high impedance into a voltage signal having low impedance (Johannes & Jan, 2012).

The sensitivity, contained in the effective operating range of frequency, is not dependent on the frequency, with the exceptions ...