Accelerometers

The most common accelerometer measures acceleration along only a single axis. You often use this type of accelerometer to measure mechanical vibration levels. The second type is a tri-axial accelerometer. This accelerometer can create a 3D vector of acceleration in the form of orthogonal components. Use this type when you need to determine the type of vibration—lateral, transverse, rotational, and so on—that a component is undergoing or the direction of acceleration of the component.

Both types of accelerometers come with either both leads insulated, or isolated, from the case or with one lead grounded to the case. Some accelerometers rely on the piezoelectric effect to generate voltage. To measure acceleration with this type of sensor, the sensor must be connected to a charge-sensitive amplifier. Other accelerometers have a charge-sensitive amplifier built inside them.

Accelerometers are the most widely used vibration transducers for measuring vibrations on stationary machine elements. The benefits of an accelerometer include linearity over a wide frequency range and a large dynamic range. You can use most accelerometers in hazardous environments because of their rugged and reliable construction.

When choosing an accelerometer, pay attention to the most critical parameters. If the sensor must operate in extreme temperatures, you are limited to a sensor that relies on the piezoelectric effect to generate voltage. If the environment is very noisy, a sensor with a charge-sensitive amplifier built in might be the only usable choice.

You can use accelerometers in applications involving frequencies from a few hertz to tens of kilohertz. The following illustration shows the typical frequency response characteristics of an accelerometer.

Because most accelerometers have a low dynamic signal response below 10 Hz, you cannot use accelerometers for low frequency measurements. The usable frequency range of an accelerometer is typically 15 Hz to 10 Hz or above.