Sensors detect tipping point in high vibration environments

Four new sensors from Memsic, the MXD6240 and 41AU, MXC6244AU and MXC6245XU, provide tip-over and acceleration sensing in automotive, industrial and consumer applications, such as motorcycle and off-road vehicle tip-over detection, vehicle navigation and digital SLR camera horizontal position detection.

They have been developed in response to issues caused by high vibration environments which have forced customers to widen the full scale range of the accelerometer to prevent clipping, and move to a more powerful microprocessor capable of higher sampling rates and heavy filtering to prevent aliasing and to recover the signal of interest. The family is claimed to be made up of the only accelerometers that have vibration-filtering.

The sensors use the company’s proprietary thermal accelerometer technology that uses heated gas molecules to sense acceleration instead of a mechanical beam structure. The transducer exhibits a natural low-pass frequency response with virtually no mechanical resonance, says the company, and accuracy over a range of temperatures. This makes the devices suited to harsh and/or high vibration environments, where competing sensors can exhibit false readings or other errors due to resonance.

The MXD6240 and MXD6241AU are autonomous inclination sensors with eight built-in, pin-programmable tip-over angle thresholds from 40 to 70 degrees, making them suitable for tip-over applications where no microcontroller is available. If the device orientation, with respect to vertical, exceeds the programmed threshold angle, the digital output changes state to alert the system to a tip-over or fall-down event. In addition to the transducer’s inherent low-pass response, an internal anti-vibration filter provides less than 45dB attenuation above 25Hz, and up to 60dB attenuation above 50Hz.

The MXC6244AU and MXC6245XU are two-axis I²C interface accelerometers, each with 1mg of resolution. The MXC6244AU is ±8g full scale range device. It includes the internal anti-vibration filter and the eight angle thresholds, programmable through the I²C interface.

The MXC6245XU is a ±2g full scale range device and is targeted at cost-sensitive applications which do not require the programmable anti-vibration filter or the eight programmable tip-over angle thresholds. It offers 12bit resolution (1mg) and over temperature bias performance of typically 0.1mg/C.

The autonomous MXD6240 and MXD6241 eliminate the need for a microcontroller and can replace older mechanical pendulum solutions in motorcycles and off-road vehicles. The MXC6244AU can be used directly in Engine Control Units (ECUs) eliminating a separate tip-over module. For applications not requiring the enhanced vibration rejection or programmable angle thresholds, the MXC6245XU still delivers the over-temperature performance of the MXC6244AU, at a low cost.

Devices pre-mounted on prototyping boards can be purchased directly from the company.


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