Ultra-Compact High Accuracy Earthquake Detection Sensor Module

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Its built-in function prevents any false detection of a seismic activity and offers increased reliability

Detecting a vibration accurately when an earthquake occurs has generated an increased interest among both rescuers and seismologists so that secondary disasters caused by fires and other factors in the aftermath of an earthquake can be prevented. Similar functions for quickly detecting damage conditions and assisting with early recovery are also demanded in various infrastructures such as buildings and roads.

However, mechanical earthquake detectors can only detect the presence/absence of vibration, and cannot distinguish whether the vibration is due to an actual earthquake or due to other external factors. Often this results in false alarms and creates an unnecessary chaos.

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In response to that, ROHM has announced the release of an ultra-compact high accuracy seismic detection sensor module, BP3901. This sensor is also ideal for automatic doors, unmanned transport vehicles, and smart meters.

The BP3901 is an ultra-compact (11.8 x 8.6 x 2.5 mm) sensor that integrates an original earthquake detection algorithm and offers high accuracy. In addition, a false detection prevention function is built in and is capable of specifically detecting the cause of vibration.

Fig 1. Block Diagram with Waveform

Key Features

  1. Enabled with high accuracy earthquake detection in a compact module form factor

The BP3901 incorporates a 3-axis accelerometer and a unique algorithm focused on determining SI (Spectrum Intensity) values. This algorithm has a high correlation with measured seismic intensity data for damage assessment while also optimising the digital signal processing of acceleration data and calculation parameters/sequence through analysis of measured excitation data.

Following 2 functions further improve detection accuracy.

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1) False detection prevention function distinguishes between seismic and external factors’ vibrations

By conducting detailed analysis of vibration waveforms and integrating a false detection prevention function, waveforms created due to external factors’ vibrations and actual seismic events are made distinguishable.

Fig 2. Detection Accuracy

2) Angle compensation function provides a mounting tolerance of ±15°

Conventional earthquake detectors can encounter problems in detecting earthquakes due to deviations in the internal seismic detection function and inclination that occurs over time.

The angle correction is achieved by combining the characteristics of the built-in accelerometer with new angle compensation operation. This allows it to check for correct inclination within the vertical planes by up to ±15° in response to the gravitational acceleration of the Earth.

Fig 3. Angle Compensation
  1. Reduced standby current consumption

The module is designed to stay in standby mode for long periods until a seismic event is detected. This is achieved with its low standby current consumption (3.5uA) by optimising arithmetic processing. For example, installing this module in a fan heater exposed to an average of 10 seismic events a month (duration: 180s/time) enables operation for up to 5 years or more on just 2 alkaline AA batteries (in series).

  1. Stores seismic data for analysis

The earthquake data is analysed and saved in a non-volatile memory when the vibration exceeds a certain level. This makes it possible to predict future earthquakes and hence do the required earthquake recovery work and maintenance prioritisation.

Availability

Samples are available now, with OEM quantities available from August 2019.

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