Precision inertial sensors are so sensitive that even noise waves can be detected as vibration. For many applications, noise is inevitable, but noise interference in the sensor’s readings is unacceptable. This post explains what causes noise disruption and how it can be prevented.
What Causes Noise Interference for Sensors
Noise comes in two forms, electrical and seismic. The power supply typically transmits electrical noise through the connection to the sensor. Seismic radiates from an outside source such as an airplane engine or a siren. When these acoustic waves are present, the sensor will detect this as vibration.
Sensors are often placed in noisy environments such as factories, trains, and military equipment. Engineers can’t afford to have noise impact their readings, but there are solutions to minimizing this interference.
Eliminating Seismic Noise with a Low Pass Filter
If engineers are certain there will be noise interference in their application, they can request a low pass filter. Upon request, the sensor manufacturer can implement a low pass filter into the sensor’s design. This component will filter out seismic noise that the sensor experiences from external sources. In order to determine if a low pass filter is necessary, the engineers need to inform the manufacturer of the level of noise and its source.
Filtering Out Electrical Noise within the Sensor Connection
Voltage output can be vulnerable to noisy environments, but a shielded connector and cable can reduce this risk. Additionally, instead of using a parallel wire configuration within the cable, a twisted wire can minimize noise.
Long cable lengths typically require 4-20mA output. This is conducive to reducing noise interference since current output is naturally resistant to outside noise interference.
Sensors that Are Vulnerable to Noise Interference
MEMS sensors have the most vulnerability to noise interference. A wider mechanical bandwidth causes a sensor to be more likely to detect acoustic frequencies. Since they have bandwidth to 400 Hz, MEMS accelerometers can be most affected, but all models can come with a low pass filter.