My new employer produces coated fiberglass yard goods. They (we) employ several mechanical devices that count the yardage on rolls of material as they are converted (ie. wound) The counters are basically wheels that ride on the material. Can anyone offer advise / direction on how to calibrate these counters. Some folks have suggested just running a 100 yard roll of material and making sure the counter reads 100 yards.....however my question would be how do I know the material is 100 yards to begin with?
thanks for any help you could provide.
Depends on the accuracy you are looking for and the acceptable errors. Best way to measure 100 yards is to use an electronic distance meter, with your material unrolled on a flat surface. Steel tapes are not good, as they have scale error subject to temperature. You also want to take multiple measurements, I'd say 10 yards, 25 yards, 50 yards and 100 yards as a minimum, a repeat over a period of time and conditions. This lets you isolate errors pertaining to scale (stretching of material, wheel size error) and offset. You also have to consider that while some errors will be systematic (e.g. wheel size calibration) others will be random (e.g. slippage). You may also have interference factors such (e.g. if the wheel is metal, its diameter will change with temperature).
Calibrating the equipment using one measurement is akin to testing a piece of software using a single happy path test. Not a great way of doing it.