In this lab you will be asked to design an experiment where you will adjust the

Question

In this lab you will be asked to design an experiment where you will adjust the inclination angle of an accelerometer and measure the voltage output of the instrument.

What instrument will you use to measure the voltage?

If the accelerometer has a linear voltage output with respect to acceleration, do you expect the voltage output with respect to inclination angle to be linear? (Keep in mind that these accelerometers can measure the static acceleration from gravity, even when sitting still.) Explain.

Explanation / Answer

Accelerometer is an electronic device which generally uses the piezo-electric effect to convert the force acting upon it to a corresponding voltage.The voltage output from the piezo-electric crytal are small and the output is analog.Hence, an ADC (analog to digital converter) along with a microprocessor is required to read the voltages from an accelerometer.
The relation between the voltage output and the corresponding acceleration/force are generally given in the datasheet of the particular accelerometer. Accelerometers with linear voltage changes are prefered as the results can be calibrated accurately.

If an accelerometer has a linear voltage output with respect to acceleration, then the voltage output with respect to inclination would be linear but would change in magnitude in the following manner:

Consider, the case where acceleration due to gravity (g) is acting in the downward direction (i.e. horizontal motion) and let the voltage output of the accelerometer be (say) x volts.

Now,when the setup is tilted at an angle (say a) the acceleration f gravity would not be equal to the acceleration g but would be a component of g.i.e. gnew = g * sin(a)Where,gnew = Acceleration due to gravity for the new inclined positiona = angle between the horizontal and the inclined plane. (i.e. the inclination with respect to the horizontal)
Now, as the voltage output with respect to acceleration is linear, the output when the accelerometer is inclined would be a function similar to that shown in equation (1).

This whole phenomenon would occur because the accelerometer can measure the static acceleration from gravity even in the horizontal position and hence as the inclination increases the component of acceleration due gravity would change giving variable output.

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