# What is Accelerometer: Definition and 159 Discussions

An accelerometer is a tool that measures proper acceleration. Proper acceleration is the acceleration (the rate of change of velocity) of a body in its own instantaneous rest frame; this is different from coordinate acceleration, which is acceleration in a fixed coordinate system. For example, an accelerometer at rest on the surface of the Earth will measure an acceleration due to Earth's gravity, straight upwards (by definition) of g ≈ 9.81 m/s2. By contrast, accelerometers in free fall (falling toward the center of the Earth at a rate of about 9.81 m/s2) will measure zero.
Accelerometers have many uses in industry and science. Highly sensitive accelerometers are used in inertial navigation systems for aircraft and missiles. Vibration in rotating machines is monitored by accelerometers. They are used in tablet computers and digital cameras so that images on screens are always displayed upright. In unmanned aerial vehicles, accelerometers help to stabilise flight.
When two or more accelerometers are coordinated with one another, they can measure differences in proper acceleration, particularly gravity, over their separation in space—that is, the gradient of the gravitational field. Gravity gradiometry is useful because absolute gravity is a weak effect and depends on the local density of the Earth, which is quite variable.
Single- and multi-axis accelerometers can detect both the magnitude and the direction of the proper acceleration, as a vector quantity, and can be used to sense orientation (because the direction of weight changes), coordinate acceleration, vibration, shock, and falling in a resistive medium (a case in which the proper acceleration changes, increasing from zero). Micromachined microelectromechanical systems (MEMS) accelerometers are increasingly present in portable electronic devices and video-game controllers, to detect changes in the positions of these devices.

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1. ### Motion detection and Location Positioning query

Hi All, I'm working on a project for my kids, objective is: - Design a system that can detect motion and report to a user (report method is not prescribed) OR - Design a system that can report the location of an object to a user (report method is not prescribed) BONUS Marks: Design a system...
2. ### Accelerometer on a dropped object

Why does the accelerometer tell me that the dropped object does not accelerate to the ground but that the ground accelerates to the dropped object?
3. ### Accelerometer vs. Gyroscope - measuring torque

Summary:: accelerometer Vs gyroscope - measuring torque Torque can be measured with an accelerometer (tangential-acceleration): t = F*r and F=m*a, so we get a from the accelerometer, giving: t = m*a*r Nm Torque can be measured with an gyroscope (angular-acceleration): t = F*r The...
4. ### I Check for geodesically-followed path in a coordinate-free way

Hi, My question can result a bit odd. Consider flat spacetime. We know that inertial motions are defined by 'zero proper acceleration'. Suppose there exist just one free body in the context of SR flat spacetime (an accelerometer attached to it reads zero). We know that 'zero proper...
5. ### Accelerometer with a Charge: Measuring Acceleration?

Suppose we have an accelerometer carrying a charge. The charge density everywhere in the instrument is uniform, or at least what I mean to say is, the charge on any component is proportional to that component's mass. Now, in an inertial reference frame, we place the accelerometer in an electric...
6. ### Unit of Velocity from a Random Walk measured by an accelerometer

Hi, I am working on a kalman filter where my measurement equation involves "-g + v" , where g is in m/s^2 and v is velocity random walk given in m/s/sqrt(hr). Feels like a stupid question, but how can I transform the unit of velocity random walk so I can do the calculation correctly?
7. ### High frequency in MEMS devices

Hello, I am designing a resonant mems accelerometer. It has a resonating beam. We are actuating it by AC voltage + DC voltage. We are going to actuate it at beam's resonance frequency. When I search for papers related to previous studies, I encounter resonance frequencies ranging from 20 kHz to...
8. ### How Do Resonant MEMS Accelerometers Detect Changes in Acceleration?

Hello, Suppose that I have a resonant MEMS accelerometer. It has a suspending beam (resonator) and I want to apply an AC voltage to the beam which will be at beam's resonant(natural) frequency. When I do this, I will create a standing wave pattern of acoustic waves (vibrations) inside the...
9. ### Force felt by the accelerometer in a smartphone

My smartphone has an accelerometer inside it. Does the phone itself and the proof mass of the accelerometer feel the same acceleration OR do they feel the same force, when I apply a force to my phone? I think they feel the same acceleration, F=ma. Force felt by proof mass and the force felt by...
10. ### I Making World's Smallest MEMS Accelerometer

Hi everyone. I want to make a very small accelerometer. (A micro or nanosized MEMS accelerometer) What do you think about this idea? I will have a source which will emit alpha particles. I will place two movable magnets at both sides of the alpha particle. When I apply acceleration to the...
11. ### Find the Acceleration and Distance from the Output of an Accelerometer Sensor

My question is kindof related to physics, as I have an Accelerometer sensor through which I am able to get the sensor data as following: x = 192 y = 433 z = -453 I need to convert these values in such a way so that It will share Acceleration in cm or meters, And also what concept I should use...
12. ### A Reference frame conversion for a moving sphere

Hi here is the situation; There's a spherical particle contained with a MEMS sensor (3D accelerometer and gyroscope) moving down a bed. What we want is to estimate the total kinetic energy of the particle. The total kinetic energy has two parts, translational part and rotational part. for the...
13. ### A Calculating Distance from Hand Movements in Surgical Procedures

I'm a surgeon, maths and physics study was a long time ago. I have been working on a project using an accelerometer and gyroscope.to.monitor hand movements during practice procedures. I thought to represent my 3 axis acceleration as a vector and then subtract from this 1g, to compensate for...
14. ### Accelerometer drop tests evaluation

Good morning everyone! I am a Medical Doctor and have a very basic understanding of physics (Studied till high school). I was very much interested in freefall experiments and wanted to do something by myself. I was interested to see if I can demonstrate the lack of gravitational pull during...
15. ### Which Accelerometer is Best for Measuring G-Force in a Car-Bicycle Collision?

I am trying to decide on an accelerometer to use that will help me measure the g-force that a crash test dummy’s head experiences during a car on bicycle collision. The dummy will be mounted on a bicycle and launched at 20km/h, it will then be struck from behind by a car driving at 30km/h. I...
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### What Factors Should I Consider when Building an Accelerometer Vibration Circuit?

Good afternoon. I am currently attempting to build a circuit for my university dissertation. I am looking to build a cct that would use an accelerometer to sense vibration from say a gearbox of a helicopter to a storage device before being transferred via Bluetooth to a laptop. My questions are...
17. ### Choosing Proper Filters for High-Speed Accelerometer Impact Sensing

I’m planning on using the ADXL375 (200g/3200Hz Bandwidth) or ADXL1001 (100g/11,000Hz Bandwidth) to measure the peak accelerations in a crash test dummy’s head during a bicycle/car crash. My goal is to sample at atleast 10,000 S/s using either a Teensy 3.6 or a Rasp Pi3. The dummy will be...
18. ### How Can I Relate Measurements from a Gyroscope and Accelerometer?

Hi Physics Forums, I have two sensors that I am trying to relate: - One gyroscopes measuring angle - Two accelerometer measuring linear speed I have put the gyroscope in the middle of a long rectangular tube. While the accelerometers are at each end of this tube. I need help getting started...
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### How to count the bicycle wheel revolutions by accelerometer

Hi, I am setting the accelerometer (BMA250E) on the bicycle wheel hub. I want to count the wheel revolutions(each sine wave) but the Speed over 20km the x-axis(a) data will increase. My question is: How to count the sine wave when x-axis sine wave position move to high or low. Thanks.
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### 2-DoF system characterization with 2 dual axis accelerometers

I've been having some trouble with this problem for a while. (Its not a homework or coursework problem) Its a part of an experimental set up that I'm building and this is a simplified version of it. I have a rigid rod which is hinged at a point and can pitch or heave about that location. There...
21. ### Accelerometer data interpretation

Hello, this is my first experience in this forum. :) I was wondering if someone can help me understanding my accelerometer data installed in a project consisting in an object that is dropped in the air from an altitude of approximately 1000 meters. The descent is controlled by a parachute...
22. ### Simple question about acceleration from accelerometer

Hi, I'm currently developing an application. I'm practically done, but I have one big issue (for me). So I have 3-axis acceleration from my android device. Now I want to have the general acceleration at time t, because after that i want to calculate velocity. So, what I know: to get velocity...
23. ### I Possible to estimate the location of a measurement point?

Hi guys, I am just wondering if it is possible to calculate/estimate the location of measurement point on a rigid body? For example, let's say we have a rigid body that is in motion. We attach a sensor, say an accelerometer on the surface of the rigid body. Now can we estimate the location of...
24. ### What is the efficiency of an accelerometer?

I 've got a project, and I 've been searching all over to find an answer; what is the efficiency of the accelerometer itself (p.e. in its use in smart-devices as screen-orientation method)? Or do you know, what is the efficiency (approximately of a regular spring (NOT into void)? Thank you...
25. ### Determining the period of a pendulum with an accelerometer

I've got an accelerometer swinging back and forth on a string collecting data. But because of the tolerance of the accelerometer, the data is not quite clean enough to simply determine when positive turns to negative, or passes through equilibrium. Here's the data. (arbitrary reading vs. time...
26. ### Reliability of low-cost accelerometers in commercial applications

My question relates to the reliability of low-cost accelerometers (MMA7455,ADXL345 etc.) in commercial products with a expected life expectancy of 5 years or more. The tilt angle reading from the accelerometer will be used as a feedback parameter to orient a single-axis plate-reflector...
27. ### How to calculate Distance from Accelerometer Data

Hi All, I am a beginner in embedded world. Currently I am working on MPU9250 motion sensor. My objective of project is to calculate the distance in real time using accelerometer. e.g. If I am at point A (i.e located at 5cm on X-axis) and I am willing to move towards point B (i.e. located at 50cm...
28. ### Mounting of accelerometer on bullet - Drop test

Hi guys, I am performing drop-weight impact tests on concrete slab. I have designed a bullet made of high tensile steel and I am interested to recorded the acceleration, then convert it to impact force. For this purpose, I need to implement an accelerometer on the bullet. I have tried two...
29. ### Need help with accelerometer data processing

Hi, am working on a vehicle tracking device, i am using LIS3Dh accelerometer to get the acceleration data. i am using TM4c1231e6pz controller. I need to implement a harsh breaking alert, I am having difficulty in finding out which direction the vehicle is moving since the axis are not aligned...
30. ### Finding Theta Angle of a Pendulum in a Moving Car | Accelerometer Question"

Homework Statement A small mass m hangs from a thin string and can swing like a pendulum. You attach it above the window of your car. When the car is at rest, the string hands vertically. What angle θ does the string make when the car accelerates at a constant a=1.20m/s^2? Homework Equations...
31. ### What Factors Affect the Impulse in a Bungee Jump?

Homework Statement An small doll is attached to an elastic cord which is suspended from a support as shown. An accelerometer is attached to the doll. The doll is allowed to fall and produces the graph shown. When the recording system is started the doll is stationary at the upper support...
32. ### Need a simple accelerometer for a demo kit

Hi, I am trying to build a demo kit to show the velocity and acceleration of a slider that reciprocates. I am from mechanical engineering background and hence need help in finding good acceleratio measurement device. My requirements are this: 1. Should be something like a ready to fit. 2. Needs...
33. ### Create a pocket pedometer just with accelerometer

Can I create a pocket step counter / pedometer just with accelerometer? If yes, can you explain how can I do that? The device should detect step irrespective of direction of device.
34. ### Orientation Detection in accelerometer

Hello, I am using accelerometer to detect orientation change.for an e.g.if mobile accelerometer senses the direction that is it in portrait or landscape mode.so basically in this method the change of axis is detected . I am using the BMA250e module as an acceleromter,which has an inbuilt...
35. ### Rotating platform on top of another rotating platform

Homework Statement Have platform A that is being spun by a centrifuge with a radius R1 and centripetal velocity of w1. On top of platform A is a Lazy Susan (Platform B) that spins about a radius R2 with a centripetal velocity of w2. There are accelerometers placed on the the purple platform...
36. ### Using accelerometer data to calculate distance

I am looking for some help, or even advice as how to proceed. I am trying to quantify an impulse from a hand (a high velocity low amplitude motion). In attempt to do that, I've tried attaching an accelerometer to my hand. My problem is, that the values I'd like to calculate as an objective...
37. ### What does an accelerometer measure?

Hi I'm confused about what an accelerometer actually measures. I downloaded an app that reads out the data of the accelerometer in my phone in all three dimensions. If I lay it flat on a table, it says something around 9.81 in the z direction and something around zero in the x and y directions...
38. ### Proper Acceleration In Accelerometer ?

Hi guys, I'm working on my project with accelerometer. I know that accelerometer measure specific force or proper acceleration in general by deflection of proof mass. Proper acceleration is relative to free fall which could be analogy that proper acceleration is the relative acceleration...
39. ### Vector Decomposition and Trig in Tension Force Analysis

Homework Statement This is a solved problem. It is attached. Why is sin theta horizontal, and cosine theta vertical? Homework Equations All relevant equations are given. The Attempt at a Solution The solution is given.
40. ### Accelerometer on a rotating wheel- Net force calculation

Homework Statement I have two analog MEMS accelerometers ADXL337, ADXL377. The ADXL337 can measure acceleration upto +/- 3g (where g = gravitational acceleration) and ADXL377 can measure upto acceleration of +/- 200g. More than this much amount of acceleration, would create noise and random...
41. ### De-noising an accelerometer with autoregression

Hi I want to ask about denoising accelerometre with autoregression after filtring high frequency noise. I analysed the noise with Burg method. To denoise the signal, I made a simulation with autoregression and subtracted it from the noised signal. Now, I have a problem. The std of the signale...
42. ### Meaning of having powerful signal near to 0Hz

Hello I computed, with python scipy.rfft, the Fourier transform of signal coming from an accelerometer. I don't understood what this is the meaning of having a powerful signal near to 0 Hz ?
43. ### How Does Material Choice Impact Miniature Accelerometer Design?

Accelerometer Design: You have been asked to help design an accelerometer with a measurement bandwidth of 1000 Hz using a cantilevered design (see figure). The cantilever (c) has a rectangular cross-section and the proof-mass (m) is 1 gram. The cantilever can be made from single-crystal Silicon...
44. ### Help with control from Arduino Mega to ADXL345 Accelerometer

So I was starting a project and have run into a small issue. I was following a tutorial and the code is not compiling correctly. The error reads as: Arduino: 1.6.3 (Windows 8.1), Board: "Arduino Mega or Mega 2560, ATmega2560 (Mega 2560)"...
45. ### Acceleration detection accounting for rotation

Hello everyone! I am trying to write an app that needs to be able to tell if a vehicle is accelerating or breaking. In this sense I used the accelerometer in the phone. At the moment I managed to isolate and subtract the gravitational pull of the Earth from my readings and I am using a noise...
46. ### Use of Gyro/Accelerometer for Boat Tilt Application?

Hello, I'm looking to try to use a gyroscope to determine the rocking motion (just side to side - not back and forth) of a boat while it is traveling forward or sitting still in the water. Specifically, I'm looking for the boat's angle from vertical and this angle's velocity. Can I do this...
47. ### What does mobile phone accelerometers actually measure

Hi Guys I am using a mobile phone to collect some accelerometer data for my walking experiments. I know this topic is done to death but a specific answer that I have never got is what does mobile phone accelerometers actually measure? Do they give the acceleration due to all the forces acting...
48. ### Interpretation of Accelerometer Measurements

I have performed an impact test on different football shin guards to assess their performance. I am however confused with the readings measured by the accelerometer I have used. The sensor was attached to a striking mass of 4.3 kg which was dropped at different heights. The graph I have attached...
49. ### Understanding use of accelerometers

Homework Statement Imagine this: A rod is attached at one end to a rotating shaft. So, as the shaft rotates from 0 to 90 degrees back-and-forth (in the xy plane), so does the rod. My goal is to measure the instantaneous acceleration of the rod while its moving. I have a few 3-axis...
50. ### How to use KALMAN with accelerometer?

hi I found an article that shows how to use kalman filter to models error of accelerometer. they used markov process as stochastic error, then output of this model will be used as input of KALMAN filter. Now, I don't what to do. I'm not sure, but I think that I need to double integrate the...