These elements are silicon beams interdigitated with two sets of stationary silicon beams attached to the substrate, thus forming two nominally equal capacitors. Capacitive SensingĪDXRS645 measures the displacement of the resonating mass and its frame due to the Coriolis effect through capacitive sensing elements attached to the resonator, as shown in Figure 4. The frame and resonating mass are displaced laterally in response to the Coriolis effect. & amp amp amp amp amp amp amp amp amp amp amp lt img src=' ' alt='Figure 4'& amp amp amp amp amp amp amp amp amp amp amp gt įigure 4. When it moves toward the center of the rotation it exerts a force to the right, as indicated by the green arrows. The mass is micromachined from polysilicon and is tethered to a polysilicon frame so that it can resonate only along one direction.įigure 2 shows that when the resonating mass moves toward the outer edge of the rotation, it is accelerated to the right and exerts on the frame a reaction force to the left. The ADXRS645 takes advantage of this effect by using a resonating mass analogous to the person moving out and in on a rotating platform. If you have a mass (M), the platform must apply a force-2MΩv-to cause that acceleration, and the mass experiences a corresponding reaction force.
There is another half from changing the direction of the radial velocity giving a total of 2Ωv. This is half of the Coriolis acceleration. So if r changes at speed v there will be a tangential acceleration Ωv. If Ω is the angular rate and r is the radius, the tangential velocity is Ωr. The acceleration required is the Coriolis acceleration. A person moving northward toward the outer edge of a rotating platform must increase the westward speed component (blue arrows) to maintain a northbound course. & amp lt img src=' ' alt='Figure 1'& amp gt įigure 1. The rate of increase of your tangential speed, caused by your radial velocity, is the Coriolis acceleration. If you were to move to a point near the outer edge of the platform your speed would increase relative to the ground, as indicated by the longer blue arrow. Your speed relative to the ground is shown as the blue arrow lengths. Consider yourself standing on a rotating platform, near the center. The Coriolis effect can be explained as follows, starting with Figure 1. MEMS gyroscopes measure angular rate by means of Coriolis acceleration. This sensor enables precision angular rate (rotation speed) measurement even in the presence of shock and vibration and is rated for temperatures up to 175☌.
To meet this need, Analog Devices has developed a new high temperature MEMS gyroscope with integrated signal conditioning, the ADXRS645. This type of abuse can cause undue wear and early failure of the system, incurring high cost in maintenance or downtime. However, there is still a need for additional degrees of freedom to precisely measure movement of the system in harsh environment applications where the end product can be subjected to severe shock, vibration, and violent motion. In addition, they can also integrate signal conditioning circuitry in the same semiconductor package.Ī high temperature MEMS accelerometer- ADXL206-has already been released that provides high precision tilt (inclination) measurements. MEMS sensors often are smaller, lower power, and lower cost than discrete sensor equivalents. However, there are still unmet needs for sensors that can operate at temperatures up to 175☌, particularly in the easy to use form factor provided by microelectromechanical systems (MEMS). In recent years there has been considerable progress in semiconductors, passives, and interconnects to enable high precision data acquisition and processing. There are an increasing number of applications that have a need to gather data from sensors located in very high temperature environments. MEMS Gyroscope Provides Precision Inertial Sensing in Harsh, High Temperature Environments