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# electronically measure poundage of an impact? Answered

I'm looking to make a training device that measures the pound force of impact from a strike. I'm sure the is a sensor out there that does this but I don't know what its called.

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## 14 Replies

Toga_Dan (author)2017-04-02

a balistic pendulum is an option.

wgriffith (author)2017-03-29

thanks guys. what I'm trying to measure is the poundage of a sword strike. I'm trying to help some friends train for tournament fighting.

Downunder35m (author)2017-03-26

Called force meter, available as sensor blocks, directional, omnidirection, impact and acceleration.
You need to know how much max force you are dealing with, get the right sensor and I suggest to get a corresponding reader or the info to build one from the manufacturer as well.

steveastrouk (author)2017-03-26

You can use an accelerometer.

Jack A Lopez (author)2017-03-26

and then multiply by m, to get F, since F=m*a.

steveastrouk (author)2017-03-26

Yup

Jack A Lopez (author)2017-03-26

So if I just put a single electronic accelerometer inside a big heavy punching bag, like maybe the kind that's mounted to the ceiling by a chain, then maybe that's the easiest way to do this using a small number of sensors and moving parts.

I mean, it would be just electronic accelerometer plus punching bag, and it's done... aside from whatever microprocessor plus software are used to interpret, record, display the signal coming from the accelerometer.

Jack A Lopez (author)2017-03-26

Oh right, but everyone has a smart phone now, with a built-in 3-axis accelerometer. So maybe just strap the phone to one side of the punching bag, preferably a side that is not being punched, input a number for the mass of the bag, and then some software can do the rest.

steveastrouk (author)2017-03-26

Got to depend a bit on just HOW much force/acceleration.

iceng (author)2017-03-26

"Description: This is a piezoresistive
force sensor from Tekscan. The harder you press, the lower the sensor’s
resistance. Pressing hard, the resistance changes from infinite to
~300k. The sensor itself is thin and flexible, but the resistance does
not change while being flexed. Resistance changes only when pressure is
applied to the round area at the end of the sensor. Used as a presence
sensor (someone standing), weight sensor, pressure sensor (impact
testing), etc.

The overall length is about 8.5". Sensor comes with 0.1" spaced, reinforced, breadboard friendly connector.

This sensor comes in three flavors. This sensor ranges from 0 to 100lbs of pressure in the mega-ohm range."

https://www.sparkfun.com/products/8685

Lower cost is https://www.parallax.com/product/30056

.. -.-. . --. -.

Jack A Lopez (author)2017-03-26

I forgot to mention, there is a sort of carnival version of the ballistic pendulum, that you've probably seen in movies, or real life. I was thinking it was called the test-your-strength game, or something like that.

It turns out that Wikipedia calls it, "high striker"

https://en.wikipedia.org/wiki/High_striker

and that page links to article with images from the 1933, September issue of Popular Mechanics,

http://blog.modernmechanix.com/boys-can-have-a-car...

and those images give a good picture of the mechanism.

If you put a right angle in that lever, then maybe you could punch it, instead of having to swing a hammer down on top of it.

Although the physics of the high striker seem, to me, to be little more complicated than the old ballistic pendulum,

https://en.wikipedia.org/wiki/Ballistic_pendulum

so the more complicated physics might make more difficult to build the "high striker" into an honest measuring device.

But what do really want? A precision measuring device? Or a contraption that can ring a bell when you punch or kick it hard enough?

cerberustugowar (author)2017-03-26

They might possibly be called load cells?

Jack A Lopez (author)2017-03-26

Hey, nice find. +1.

The device they're using to measure force is called a "load cell",

The time integral of force is called "impulse"

https://en.wikipedia.org/wiki/Impulse_(physics)

And impulse is equivalent to a change in momentum

https://en.wikipedia.org/wiki/Momentum

If you want a purely mechanical device for measuring impulse, a ballistic pendulum (first invented in 1742) can do this.

https://en.wikipedia.org/wiki/Ballistic_pendulum

Actually the BP was designed for measuring impulse delivered by a bullet, but punching it might work too.