of medicines). At the opposite end glue a piece of wire shaped, or a piece of plastic cut to the required form, so that it is free to move outside the cylinder. On the outer side, near the tip folded, glue a strip of paper on which we report a series of dashes graduated. The operation is very simple: if reggiamo with his hand on top of the spring hook and hang on to the lower weight, the spring will expand in proportion to the weight. The tip will fall down and will indicate a different location than the initial one. To calibrate our dynamometer we have to hang a bag on the hook every time less and introduce a measure of something, sand, rice or whatever. Obviously, we will use weights appropriate to the spring, bearing in mind that there are springs which extend with only gr. 100 of bearing weight, and other dozens of kilograms. Remember that if we overburden the spring beyond its limits, it will deform permanently and no longer work.