Accelerometers

• THE TECHNOLOGY

Murata‘s MEMS sensors use the change in electrical capacitance due to acceleration. This technology has several advantages. Capacitive sensing potentially provides measurements over a wide operating temperature range without compensation. Capacitive sensors can monitor static as well as dynamic phenomena. These two advantages allow capacitive accelerometers to be used for many applications. This sensor is composed of :

A sensitive part (sensing element): Composed of two silicon wafers and a pendulum. Subject to an acceleration, a movement occurs around the pendulum. On the surface of the substrate, below the plates of the pendulum, two conductive plates are present and thus form two variable capacitances (with a common connection). This creates a fully active capacitive bridge. As the pendulum rotates around the axis, the average distance between one of the plates and the surface decreases, thus increasing the capacitance of this plate, while the average distance of the plate on the other side of the axis increases, thus decreasing its capacitance.

An ASIC integrated circuit, which transforms the variation of the capacitance into voltage, to provide an analog output, the assembly being sealed to provide a simple and perfectly hermetic device, able to withstand harsh environments. This standard accelerometer can be easily assembled on an electronic board and is used to manufacture all the modules and thus allow to measure acceleration.

On this principle Murata offers 3 families of products :

• • Inclinometers

Capacitive inclinometers use the natural earth gravity of 9.81m/s2 to modify the capacity between the Mems’ feeder, our inclinometers measure the inclinations in the 3 axes X Y and Z. The most accurate is available with Murata‘s SCL3300. This sensor also has a direct tilt angle output, making it a perfect choice for a variety of different use cases and applications. Due to its design, the inclinometers offer one of the best fatigue resistance, and can withstand accelerations of more than 20,000 g. Typical applications of these sensors are typically in levelling systems, inclination detection, machine control, building monitoring, Inertial Measurement Units (IMUs), robotics, positioning and guidance systems, position evaluation Drilling: inclination evaluation, position monitoring …

• • Accelerometers

Murata is the global market leader in low-g acceleration sensors.  Accelerometers are primarily used in automotive applications. Murata’s broad range of industrial accelerometer products includes high-performance analog accelerometers for safety-critical automotive and industrial applications. These Industrial Accelerometers offer a number of excellent features for the most demanding applications. The sensing element and measuring ASIC are assembled in a housing for cms mounting. They are protected from the environment with silicone gel, providing excellent performance and reliability in humid environments and over wide temperature ranges. In addition, the robust design of the sensing element with an over-damped frequency response allows excellent performance even in harsh and vibrating environments, and allows very high amplitude acceleration. In summary, Murata industrial accelerometers have excellent accuracy, high stability, low noise, stable output over a wide temperature range, and withstand wet environments and vibration.

These accelerometers are generally used in automotive safety systems: suspension, airbag, Stop and Start, Anti-lock Braking System (ABS), Hill Start Assist (HSA), Rolling Stability Sensor (ARC), Roll Over Vehicle (ROV), but also in IMU inertial units, or for industrial applications.

• • Gyroscopes

Industrial gyroscopes offer a level of performance that was usually only available in expensive module products. The sensing elements and measuring circuits are assembled in a pre-molded double in-line (DIL) plastic housing, protected with silicone gel and covered with a stainless steel cover. All products are RoHS compatible. We also offer you a combi-unit that combines accelerometer and gyroscope in the same housing. By combining an accelerometer and a gyroscope in one rugged unit, Murata offers a high level of performance. Target applications include inertial power plants, control and stabilization of the accelerometer and gyroscope.

All angular velocity sensors are insensitive to shock and vibration.

They are thermally compensated over the entire operating range from -40°C to +125°C.

Gyroscope stability is less than 2 °/h and polarization accuracy over the entire temperature range <±0.6 º/s. The combined versions have two separate digital SPI interfaces (one for the gyroscope, one for the accelerometer).

• Main application areas

These products are mainly used for platform stabilization, motion analysis and control, GPS orientation and navigation systems, and mass-spring systems. Generally speaking, to facilitate the design process and validate the choice of component, Murata offers a demo-kit with an evaluation board that integrates a graphical interface for the accelerometer and gyroscopic inclinometer versions. The production plant is in Vantaa, FINLAND.