Each contact comes with a value called total_force, which is the force of the contact in grams.
You can learn more about what information you can get from a contact from this API primer: guide.sensel.com/api/.
You can see all the possible elements in the contact struct here: (guide.sensel.com/sensel_h/#SenselContact). But if you need some of the more complex data (deltas, bounding box) look into senselSetContactsMask (guide.sensel.com/sensel_h/#senselSetContactsMask) which is detailed in the primer.
Hope this helps.