0

Pretty much what the title states.

The Android CDD says of the Accelerometer

  • MUST be able to deliver events at 50 Hz or greater
  • MUST comply with the Android sensor coordinate system as detailed in the Android APIs (see [ Resources, 41])
  • MUST be capable of measuring from freefall up to twice gravity (2g) or more on any three-dimensional vector
  • MUST have 8-bits of accuracy or more
  • MUST have a standard deviation no greater than 0.05 m/s^2

So I find myself wondering - would it be possible to measure one's mass by taking a short hop with the device strapped to chest/waist? The raw accelerometer data would provide the duration and acceleration encountered on both upward/downward leg (pun unintended) of the hop.

ale
  • 19,723
  • 34
  • 110
  • 159
Everyone
  • 173
  • 1
  • 6
  • 2
    This doesn't seem to be Android specific, but is a physics question? – GAThrawn Mar 28 '12 at 14:09
  • Mitthrawnuuruodo, Although there is physics involved we're seeking a match on accelerometer that comply with the Android CDD – Everyone Mar 28 '12 at 16:09
  • The constraints on the problem being provided by the Android CDD don't change the nature of the problem. This is not an Android question. – Matthew Read Mar 28 '12 at 21:13
  • 1
    Going by that metre-stick, neither is http://android.stackexchange.com/questions/15260/how-does-in-pocket-detection-work – Everyone Mar 29 '12 at 11:00

1 Answers1

2

Newton's second law states that Force = Mass * Acceleration. We can use this formula to solve for Mass:: Mass = Force / Acceleration. As such, we need a known force in order to take a measurement of acceleration to determine mass. Hopping into the air is going to be a variable, instantaneous force. Also, your legs are going to act like variable force springs to absorb your impact with the ground. All of these variables would really frustrate your attempt to get anything close to a valid mass reading.

NASA has created device that uses the measurement of acceleration to determine mass for astronauts in space. The Space Linear Acceleration Mass Measurement Device (SLAMMD) uses two springs to generate a known force on the subject and then reads the acceleration to determine mass. There is a nice video on YouTube explaining how it works and providing a demonstration of the device in action.

JadeMason
  • 2,270
  • 3
  • 21
  • 26
  • You're right. But the mention of springs points me at another idea ... albeit not SmartPhone, or even Android specific. Here, in India, a truck must carry a proof of weight issued by a weigh-bridge over and above the bill of lading. A calibrated transducer at the right point in the suspension could cut down on the long queues/time getting each truck weighed. – Everyone Mar 28 '12 at 16:14