Portable tennis ball testing device

A portable device for use in determining whether a tennis ball complies with a pre-established deformation standard, comprising:

• a frame including a plurality of support rods extending in parallel relationship with one another;
• a first plate and a second plate fixed to said support rods and disposed in spaced relationship to one another;
• a ball-compressing sliding component disposed between said first plate and said second plate, said ball-compressing sliding component including:
• a third plate and a fourth plate coupled to said support rods for mutually independent sliding motion along said support rods;
• and
• an elastic element or spring of predetermined height and a predetermined monotonic force vs. distance function F(x), said elastic element or spring being disposed between and in contact with said third plate and said fourth plate;
• means for moving said sliding component so as to compress both said elastic element or spring and a ball inserted between said second plate and one of said third plate and said fourth plate;
• means for limiting a compression distance of said elastic element or spring to d=F−1(f), where the force f=F(d) required to compress the spring the distance d has a predetermined value;
• and
• means mounted at least indirectly to said support rods for measuring a degree or deformation or compression of the ball.