Memsic 2125 and Acceleration Due To Gravity
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An experiment I'd like to perform on a high balloon flight is to measure the
decrease
in the acceleration due to gravity as the altitude increases. I calculated that
g will
decrease by 1% at 100,000 feet.
Will the 2125 measure the acceleration due to gravity? If you take measurements
and then drop it, does it's output record that fact that it is in free fall?
Paul
decrease
in the acceleration due to gravity as the altitude increases. I calculated that
g will
decrease by 1% at 100,000 feet.
Will the 2125 measure the acceleration due to gravity? If you take measurements
and then drop it, does it's output record that fact that it is in free fall?
Paul
Comments
Original Message
From: <verhap@o...>
> An experiment I'd like to perform on a high balloon flight is to measure
the decrease
> in the acceleration due to gravity as the altitude increases. I
calculated that g will
> decrease by 1% at 100,000 feet.
>
> Will the 2125 measure the acceleration due to gravity? If you take
measurements
> and then drop it, does it's output record that fact that it is in free
fall?
>
> Paul
Yep, acceleration is acceleration is acceleration to an accelerometer. In
climb, the output will correspond to the acceleration of gravity + whatever
upward acceleration is being experienced in the climb. In free-fall, the
output will correspond to 0g, because the accelerometer is not experiencing
any acceleration.
As far as measuring the change of gravity with altitude, I'm not sure that
the Memsic accelerometer will work for you. You might be hard-pressed to
distinguish an output for .99g from the output for 1g, at least with any
degree of reliability. Look around for some more sensitive accelerometers -
they might work for ya.
- Robert
vector of gravitational force and linear acceleration components. If
your balloon is buffeted by winds, there will be additional
acceleration, adding and subtracting from g from moment to moment.
An accelerometer dropped in a vacuum will report 0 output (free fall).
When dropped in an atmosphere, it will reach a terminal velocity that is
more or less constant, and therefore also close to 0 acceleration.
The Memsic, which I think is based on expansion/compression of a gas
bubble, would not be a good choice over wide-ranging atmospheric
pressure. Other sensors (Analog Devices ADXL202e) would be better, if
kept at constant temperature in a small oven.
Dennis
Original Message
From: verhap@o... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=E0wgUlbD1vuNj9-IiWzwJr6Driz3wSIwsIJ5EJxx98yZ_0hn8rFbf9I4ytOnS3HhASrBNVrRgLn6Nbypyo3luBjH]verhap@o...[/url
Sent: Wednesday, January 14, 2004 10:52 AM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Memsic 2125 and Acceleration Due To Gravity
An experiment I'd like to perform on a high balloon flight is to measure
the decrease
in the acceleration due to gravity as the altitude increases. I
calculated that g will
decrease by 1% at 100,000 feet.
Will the 2125 measure the acceleration due to gravity? If you take
measurements
and then drop it, does it's output record that fact that it is in free
fall?
Paul
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