Everyone needs a hardness tester.

[tonyfoale]

Wow! This is very cool. Very generous of you to share. Not sure if I will have the electrical ability or the knowledge to make an Arduino work. But I am going to give it a try. Always wanted a reason to try out an Arduino.

Try it out. There is nothing to lose and you will learn something whatever happens. I think that you can buy the Arduino Nano for something like $15 for a pack of 5. The other electronic bits are also super cheap. If you had none to start with I doubt that you would to spend more than $5 to get everything for this project.
These days getting started with electronic projects is so much easier than it was in pre-micro days. Now you get something like an Arduino, Pi or ESP32 and you have a device which is the equivalent of thousands of transistors arranged in a general purpose way which can be used in specific circuits just with software. Decades back you had to design and construct individual circuits for each application and the components were much more expensive. I was 8 when I first started building radios etc. and I had to save pocket money for months just to buy a single valve.
It takes a minimum of electronics knowledge nowadays to build quite complex and useful devices.