Converting Strain Gage Voltage to Force for Scientists

[trannh]

Hello,

I am doing a project where I have 4 strain gages (in a full bridge Wheatstone configuration) and I am continuously recording their output voltages. These strain gages have been installed on an aluminum bar and are recording bending. My question is how to I convert the output voltage that I am recording into an actual force in, say Newtons or pounds? I am aware of the equations to get Vo and the gage factor, but is there a way to convert that information into an actual force measurement like N or lbs? Thank you very much for any help.

 

[NascentOxygen]

Can you calibrate the sensor by subjecting the rod to various amounts of force (at the desired point of application) and graph your measured data of this force vs. voltage?

 

[trannh]

So you mean manually applying different known forces, reading the output for each, and then using that relationship to estimate forces depending on what output voltages are recorded?

 

[jim hardy]

strain gage measures strain not force.

think "Young's Modulus"...

 

[NascentOxygen]

So you mean manually applying different known forces, reading the output for each, and then using that relationship to estimate forces depending on what output voltages are recorded?

Yes, that's what I was suggesting because I read it as you wanting to use this setup to measure a force applied at some point on the rod ("Strain gage voltage to force"). Perhaps you have something different in mind? If you are wanting to measure the strain the rod is under, then jim hardy has pointed the way.

 

[trannh]

An example would be a treadmill bar. Let's say I wanted to measure the force a user is applying downward onto the bar, I would place the strain gages in a configuration under the bar, to create a load cell essentially. My goal is to convert the output voltage from such a configuration to a force. I'm not quite sure how to though. Applying different known forces and recording the voltage output and plotting them to find a relationship seems to be the best option, that way, when someone is putting an unknown load, by analyzing the output voltage, I can get an estimate on how much force they applied. Is this correct?