Based on how much force is applied, that is how much current flows. Piezoelectric accelerometers are extremely accurate and used in many industrial applications. Items like smartphones and wearable technologies need accelerometers for many different uses like screen rotation and advanced movement analytics, but they cannot hold accelerometers like the piezoelectric model as it is much too big to fit.
All the components of the accelerometer are etched onto silicon instead of wrapped in an outer casing like with the prior two examples. This is where it gets its name from. It is essentially a micro-sized system that brings in mechanical processes acceleration with electrical ones. At a high level, MEMS accelerometers work using the same guiding principles of mass and spring but use them to create differing capacitances instead of voltages or pen lines.
Zooming in, the structure of the accelerometer will look like the diagram below. The mass is attached to springs on both sides that will move in the direction of the acceleration. Also, on the mass there are plates that are attached to it and move as it moves blue and fixed plates that are not attached to the mass green. The movement creates altering distances between the blue and green plates, which creates a different capacitance for each region red regions.
Based on the change in capacitance, the acceleration that caused that change can be calculated. These movements are microscopic, but because it is already integrated on the circuit board, that information can be directly applied for other device uses. Accelerometers have a vast range of uses and therefore different types exist to suit each specific use.
MEMS capacitors allow for mobile devices like smartphones, wearables, and even telematics hardware to accurately detect changes in acceleration while minimizing space and staying within the main circuit board. Since the accelerometer does not respond to gravitational acceleration, it never detects gravity directly. Since it detects deviation from freefall, its reading can sometimes be used to infer the properties of local gravity if we utilize other knowledge of the situation that we may have.
Imagine that we are in a little box with the accelerometer, and all we know is the reading that it is returning. Based on that knowledge alone , we can never determine the direction or strength of gravity. But now, consider injecting selected other knowledge-in particular, knowledge that relates our deviation from freefall to the local gravity vector. For example, if we know that we are stationary on the tabletop, we can infer both the direction and the strength of the gravitational field: It is exactly equal and opposite to the accelerometer reading.
At the other extreme, if we are in freefall, the accelerometer reads zero and we can't infer anything about the direction or strength of gravity. The only way we can learn anything is to open the window and look outside, taking note of the passing scenery to deduce which way we are falling. The accelerometer is no help at all. Not too surprisingly, the intermediate case of the angled table is also intermediate in what we can infer. For example, suppose we know that we are sliding down the angled table top.
If we also know either the angle of the table top or strength of local gravity, we can use simple trig to determine the other. Given the angle, we know that "down" lies somewhere on the surface of a cone that we can compute, but we can't say any more than that. In other words, compared with the level table top, we can't infer quite as much about local gravity given the equivalent extra knowledge. Inside the rocket, we can sense drag and thrust. These determine our deviation from freefall, but since they have no particular relation to gravity, we can't use the accelerometer reading to find "down".
Of course, if we already know the relation of the deviation vector to gravity, we can find "down". For example, if we know that after 15 seconds, our rocket will be headed straight down at zero thrust, we can say that the accelerometer will register a drag vector that points straight up.
But to deduce this, we already used our knowledge that the rocket was headed down, so the accelerometer reading isn't adding any new information about this. Create a free Team What is Teams? Learn more. How to determine linear acceleration using an accelerometer? Ask Question. Asked 3 years ago. Active 2 months ago. Viewed times. Can some one help me please? Improve this question. Vishnu 4, 5 5 gold badges 21 21 silver badges 65 65 bronze badges.
Tiago Portela Tiago Portela 13 2 2 bronze badges. They do not and cannot sense gravity. They sense acceleration due to every force except gravity. An accelerometer at rest on a table registers an acceleration of 9.
How could this happen if accelerometers sensed gravity?
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