How are the references set on a height gage? There are two main references to set when using a height gage: the internal zero and the ball diameter. A couple of key checks to run initially when setting these references are very important. First make sure that the surface plate used to set the internal zero is completely clean of any debris or dust; same goes for the ball. Second, make sure that both the surface plate and the ball are securely attached to the height gage and not at all loose. Both of these could interfere with the precision of your measurements. In order to set the internal zero of the surface plate, lower the sensing head and touch it to the plate. This will then be your baseline zero for any further measurements. Setting the reference of the diameter of the ball is equally important. The standardized text fixture and routine that accompanies your height gage should be utilized to set this reference point. As an extra precaution, the process of setting each of these reference points could be repeated a few times to ensure precision.