Do you have a Discount Tire (America's Tire in some states I think) near you. When I was discussing my frustration with shops using impacts to finish, they said NEVER HERE and we check ours daily against our tester ... I didn't see it, but the manager said that since I asked, they'd checked the one used on my F150 right before tightening mine. Perhaps, with their superb customer service, they'd do a quick check on yours? If it is a load cell type, they can observe its reading when yours shows maybe 50, 100, and 150 and say if you need to do anything.
As others mentioned, the construction looks like a beam style with a dial indicator ... inherently good unless totally broken.
Problem with weight and length is where the weight is applied; in concept that is the best way I know.