Linear actuator design

hello,

I want to create a robot that performs somewhat of a "hardness test". I was thinking about using a Tubular Rack Actuator. In determining the hardness of a material, the robot will feel a greater resistance with a harder material (and not so much with a softer one). My concern is: will the Tubular Rack Actuator have a feature/sensor (or wire that I can connect to the microprocessor) that will measure such a resistance. Will I have to buy a sensor? If I, what kind should get?

Another idea was connecting a spring to the end of the actuator. Depending on the displacement of the spring will tell me what material I am testing. How can i measure that?

Any help will be greatly appreciated. =)

Do some online searching for a Rockwell Hardness tester. You will get a good idea of how they work.

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