What are the relevant knowledge of the acceleration sensor?

For most engineering applications, choosing the right test tool will have a great impact on the test results. How to choose an acceleration sensor correctly, let us start with the classification and principle of the sensor.

Basic acceleration sensor type

    Generally speaking, there are two types of acceleration sensors: AC response acceleration sensors DC response acceleration sensors.

    As an AC response accelerometer, as its name, its output is AC coupled. Such sensors cannot be used to test static acceleration, such as gravitational acceleration and centrifugal acceleration. They are only suitable for measuring dynamic events. The DC-responsive acceleration sensor has a DC-coupled output and can respond to acceleration signals as low as 0 Hz. Therefore, the DC response acceleration sensor is suitable for testing static and dynamic acceleration at the same time. It is not only when you need to test static acceleration to choose an acceleration sensor with DC response.

Acceleration, velocity, displacement

    Many studies on vibration require information on acceleration, velocity and displacement, which are important information that engineers need when designing and verifying structures. Generally speaking, acceleration provides a good reference, while velocity and displacement are the variables required for calculation. In order to calculate the speed and displacement from the acceleration, the acceleration signal output from the sensor will be integrated once and twice in the form of digital or analog respectively. This may cause problems with AC-coupled sensors. To demonstrate this problem, imagine using an AC sensor to measure a wide pulse half-sine wave signal. Due to the limitation of the inherent AC RC time constant, the output of the sensor cannot match the input pulse well. For the same reason, at the end of the pulse, the sensor output will produce a negative zero offset. The figure below shows the relationship between the output of the sensor (red curve) and wide pulse half-sine acceleration input (blue curve).

    This seemingly small difference in amplitude will produce a significant error after integration1. DC-responsive acceleration sensors do not have such a problem, because their output can accurately follow the slowly changing input. In actual daily applications, the input signal may not be a pure half-sine pulse, but such a problem will always exist when an AC-coupled sensor is used to test any slowly changing signal.

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