3 Strain gauges

Hi I am working on a project for school and would like to use an arduino to connect 3 120Ohm strain gauges to my computer and display a live graph and data. The reason for 3 strain gauges is because I am trying to measure the strain on a barbell so using 3 strain gauges eliminates any issues with the barbell rotation. I have read that I will need to use a amplifier, but most amplifiers I have found require 4 wire strain gauges.

The strain gauges I will be using are

Model: KFH-6-120-C1-11L1M2R


What are my best options to achieve this? I am brand new to Arduinos but have been told it is a great way for me to set up my project.

Any suggestions or information is greatly appreciated

Thank you

Strain gauges are mostly used in either voltage divider or bridge configurations, with four forming a Wheatstone bridge, to reduce the effects of temperature variations.

You can use a resistor in place of a strain gauge as one or more of the elements in either configuration, but then you may have to compensate for temperature changes.

Ok If i do use a resistor in place of the strain gauge. How do I go about interfacing it with the Arduino? I have done some research and have found a few load cell amplifiers? But they are focused on load cells that are 4 wire setup. I am not an EE or very familiar with Arduinos. Any information getting me in the right direction will be greatly appreciated

Four wire cells are Wheatstone bridges with two excitation leads and two signal leads.

Any of the arms of the bridge can be replaced by a passive resistor, but then you may need temperature compensation.

It is unclear how you intend to use the gauges that you have. Post a diagram showing their placement and what each is supposed to measure.

I suspect the idea is to have them longitudinal to the bar, spaced 120 degrees apart around it, so that no matter what the bar's rotation is they can measure the amount of flexing.

If you measure the no-load value for each one, then when you measure the differences under load for each of the three you can turn that into a quadrature value using the Clark transform https://en.wikipedia.org/wiki/Alpha%E2%80%93beta_transformation

and its easy to compute the amplitude of a quadrature signal using Pythagorus.

Maybe try to choose other types of strain gauge. Please think about optical strain gauge or mechanical strain gauge. The calculations will be harder but the accuracy will be better.

Use 4 strain gauges instead of 3. Now wire them up to detect bending and you will find you have 4 nodes to connect to.

I think the Omega site has a diagram for this. It is not super-clear however.