I show you a little device that I built so I can explain more things related to strain gauges, Wheatstone bridges and differential amplifiers. My circuit is not new, in fact, I reverse-engineered an already existing circuit from AliExpress. The circuit is an easy-to-find strain gauge amplifier module. It is a neat little circuit with a built-in Wheatstone bridge and a dual OP-AMP (typically an LM358 or a TP09) with a potentiometer to shift the output voltage. I already used this circuit in some of my older videos.

The original circuit is made with SMD components, so it takes time and effort to understand the circuit. I know that there are schematics shared on the internet, but as a practice, I first reverse-engineered the circuit with a multimeter in continuity mode, and then I looked at the publicly available schematic to see if I made any mistakes. Then, I designed a PCB with through-hole components to make it easy to replicate. I added a bunch of test points to places where it can be interesting to measure the voltages. I designed the board in a way that it can potentially be used for example in an electronics lab at a school where the students have to learn about strain gauges, Wheatstone bridges and operational amplifiers. I think this circuit is very useful to understand the concepts of these previously mentioned components.

In my circuit, I used passive components with 1% tolerance which seemed to be a mistake, or at least it created a "not too optimal" situation when I tried to compare my measurements with the formulas. When it is possible, go for components with 0.1% or even 0.01% tolerance and try to match the components as well as possible, especially for the first stage of the amplifier.

For the parts list, please check the attached interactive BOM.