The reference for all calculation and scaling of time is a quartz crystal on one of the data-acquisition boards that interfaces between the computer software and the machine. This includes dwell time during sealing, and cooling time after the jaws open.
For dwell time, the monitor displays a graphic of sealing pressure (or force) vs. dwell time, in milliseconds. The cooling curve is a plot of force vs. time after jaws open, in milliseconds. In both cases, the actual scale of time shown on the plot is calculated by the computer from the crystal frequency, employing appropriate algorithms.
To check the accuracy of scaling by independent means, a calibrated digital oscilloscope is used. The input to the oscilloscope is connected to the output of the machine's load-cell amplifiers. Forces associated with either sealing pressure or peel of the seal during cooling are then measured by the oscilloscope vs. the scope's calibrated time source. We allow a tolerance between the oscilloscope and machine readings of the larger of 2 ms or 0.2%.
