Internet PLC Forum

Our company is in the process of purchasing an automated system that will be performing soldering operations.  We are looking to validate the solder process, and as a result we are currently considering trying to "calibrate" the PLC timer.  I don't believe this is a value-added effort.  I am not so much concerned that the timer is accurate, but that the amount of time measured will not vary over time.  To put it another way, I'm not concerned whether or not the time elapsed is accurate, but that the measured time elapsed will remain the same over a period of years.  I was wondering if there is any documentation or studies out there that may have addressed this issue, and I would appreciate any help in finding an answer for me.