Is there an instrument for measuring the force of spring compression?
Measuring instrument of course, but if your purpose is to want to know a few years after the spring compression (compression) and whether the length of compression strength and mechanical just installed in that case, I suggest you do not measure, certainly not the same! You should think about the frequency and environment you use, and for several years you must be tired! I do this line, I know.
It's OK to add a special jig to the connection of the height gauge and the push pull meter.
It is OK to install a digital push indicator on a height gauge! Depending on the accuracy you require, choose whether you need digital or pointer type.