They let you know what weld pressure you are getting at any time.
Force gauges eliminate the shortcomings of computing weld pressure.
Figuring from a standard air gauge reading can be inaccurate because weld cables or water hoses can impede strokes, or the air gauge itself may be incorrect. These are compact, direct-reading instruments. They operate on a closed and sealed hydraulic system and require no maintenance. This is the most precise force gauge available anywhere. Maximim reading is 3000 lb, in 20-lb increments.