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G-Force Accelerometer conversion to Pounds per Square Inch

by MAPhysics
Tags: accelerometer, conversion, gforce, inch, pounds, square
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Jun21-09, 12:53 AM
P: 2
So, the title says it all. background info on this question. I purchased a Herman Digital Trainer. It measure the impact of punches and kicks based on G-Forces. I was wondering if it was possible to a G-Force reading into Pounds per square inch reading.

This is the websites description of the calculations used:
The Herman sensors are queried every 10ms. The sensor returns the highest reading for each axis (X,Y, and Z) that it has read since the last time it was queried.

The value is subtracted from the resting/idle value for that axis.

Herman takes the three axis readings and determines the magnitude of the sensor reading using standard vector math. This effectively takes into account the energy from all three axis simultaneously.

Vector Magnitude = square root (X*X + Y*Y + Z*Z)

This value is then scaled from a digital reading to G forces knowing the maximum reading on each sensor is 40G.

This value is then multiplied by 2 yielding the score for this sensor reading. Effectively, the scores in Herman are two times the G force of the impact. A score of 20 correlates to an impact of 10G on the accelerometer.

If someone is able to assist me by giving me a conversion equation it would be most appreciative. Note. Highest form of math I've taken is Calculus, I will be taking Physics 213 in the fall, so I might need an explanation of the equation. Thank you for taking the time to read this.
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Vanadium 50
Jun21-09, 02:30 AM
Vanadium 50's Avatar
P: 16,177
G-Force is not a force; it's an acceleration. Pressure is not a force either: it's a force per unit area. So there won't be a simple conversion: that's like asking for a conversion between degrees and gallons.
Jun21-09, 04:04 PM
P: 2
I figured that. But they are both being used to determine how hard the impact of your punch and kick. So I assume there has to be a way to link the two.

Jun21-09, 05:13 PM
P: 2,043
G-Force Accelerometer conversion to Pounds per Square Inch

Acceleration in G (a=readingx9.81) -> Force by (f=ma) -> Pressure by (P=F/A)

Obiously you'll need some data about the area of punch A and mass of the parts accelerated.

This is by no means totally accurate but gives a nice ballpark figure.

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