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### Topic: Acceleration Measurement (Read 1 time)previous topic - next topic

#### bronco9588

##### Sep 15, 2013, 10:07 pm
Hi,

I would like to try to measure horsepower from an accelerometer. If I collect acceleration data WRT time and perform some integrations, I will be able to calculate velocity and position. From there with some drive train calculations it should be pretty easy to calculate torque and horsepower. I need one axis and a 2 g accelerometer. I would like to collect as much and accurate data as possible to do my integrations. My plan is to use a memsic 2125 accelerometer. It is low cost, meets my g requirement, and axis requirement. From my reading there are 100 hz and 400 hz models? The accelerometer puts out a pulse signal, so I wouldn't even have to perform an ADC.

What is the best way to collect this data? Should I look at getting a SD card shield? How many samples per second can the arduino uno collect? 16 msps?

#### Erdin

#1
##### Sep 16, 2013, 09:30 pmLast Edit: Sep 16, 2013, 09:35 pm by Erdin Reason: 1
Did you really say: 16 Mega samples per second ?
Or: 16 milli seconds per sample ?

By the way, that sensor is an expensive freaky weird old and outdated sensor. Why would you use a frequency output, when the Arduino has a I2C bus, a SPI bus and analog inputs.
There is a simple sketch for it: http://arduino.cc/en/Tutorial/Memsic2125
(But I still don't like that sensor)

Don't set high hopes on calculating the position. The MEMS sensors are noisy and drift.
http://en.wikipedia.org/wiki/Microelectromechanical_systems
I did see a few projects that calculate the position. Perhaps one was on www.hackaday.com

#### Chagrin

#2
##### Sep 17, 2013, 12:04 am
There was a post on hackaday where an accelerometer was used to track the position of a person's shoe as they walked. The only reason this worked is because the user could count on their foot being motionless every step and at a known position (on the ground!).

But no, you can't hope to put an accelerometer in a car, for example, and have any sort of sane result beyond the first two seconds.

Practical rate of recording samples would be around 1000-10000 samples/second. Commodity MEMS accelerometers are only capable of outputting data at ~1000 samples/second.

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