Eaton Cutler-Hammer Durant PRESIDENT Series Installation And Operation Manual

Contents

SCALE FACTORS31each successive part grows longer by 0.004inches. Eventually, this cumulative error will causethe part to be out of tolerance.Typically, those applications which require Func-tion 83 to have a value of “1” are cut-to-lengthapplications. When the application is performing arepetitive process such as punching equallyspaced holes in a single part, the scaler shouldretain partial counts for the next measurement. Inthese cases, Function 83 should be set to “0”.Whenever the Reset key is pressed or the ResetInput is energized, the scaler is always reset, elim-inating any remaining partial counts. This isregardless of the value entered in Function 83.CALCULATING THE SCALE FACTORThere are four general categories of applicationswhich require scaling. The method of calculatingthe scale factor differs for each. The categoriesare:1. Allowances for wear of measurement devicesand material stretch applications.2. Unit conversions (typically when the measure-ment system is set up for measuring one unitand the part must be made in another; i.e.,inches versus millimeters.)3. Scaling of pulses received from flowmeters orother sensors which produce a non-standardnumber of pulses per unit of measure.4. Allowing multiple parts to be made for eachoperation of a machine.A discussion of the means of calculating the scalefactor for each category and special problemsinvolved follows.Allowances for Wear or StretchOver a period of time a measuring wheel will beginto wear. The wheel allows accurate measurementonly when its circumference is a known, fixedvalue. Thus, as the wheel wears, the error in themeasurement increases because the circumfer-ence of the wheel becomes less and less. Scalingprovides a means to compensate for the decreas-ing wheel circumference. This allows the useful lifeof the measuring wheel to be extended, decreas-ing cost.In applications where the material stretches orshrinks by a fixed amount, scaling allows compen-sation for gained or lost material. These applica-tions required that the amount of stretch orshrinkage be known, measurable or calculableand that it be consistent from machine cycle tomachine cycle.In either case, the scale factor is calculated byusing the formula:Measured or Calculated DistanceScale Factor = Theoretical DistancePULSESRECEIVEDRESULTCALCULATEDDISPLAYVALUESECOND CYCLERESULTSECOND CYCLEDISPLAY1234567891011121.30002.60003.90005.20006.50007.80009.100010.400011.700013.000014.300015.6000123567910111314151.90003.20004.50005.80007.10008.40009.700011.000012.300013.600014.900016.200013457891112131416Figure 25. Pulses Received versus Display Value Using Scale Factor of 1.3000