Having worked in factories my whole life, I have used scales for weighing trucks and pallets for years. However, when it comes to scale calibration proceduresI know very little. In the past if my scales were acting up, I just called our local guy to come out with his test truck or weight cart. He would take a look around the scale, make a few adjustments, put weights on it and then he would say that he was going to calibrate it. I never really understood what that meant. So one day I asked. He said calibration of a scale is a procedure in which I place a known certified test weight on the scale to adjust the response of a mechanical or electronic weighing system. The indicator must show zero when there is no weight on scale. Then, when a known weight is applied the indicator must display the exact amount of applied weight within a specified tolerance. When weight is applied or removed incrementally the scale must display weight equal to that on the scale within a certain tolerance.