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Weighing Applications

Rate of Change by Weight (ROC)

Typically deployed in two manufacturing areas: MAKE (batching and blending) and PACK (filling and dispensing). Rate of change (ROC) is normally used to measure the rate at which material enters or leaves a weigh hopper. It may be used in either “gain in weight” or “loss in weight” applications.

ROC is a weight change over time. For example, if material is being taken off the scale the ROC will display a negative value; if material is being added onto the scale the ROC will display a positive value. If no material is being taken on/off the scale, the ROC value will be ZERO.

The value is dependent on the time constant selected, for example lbs/min, lbs/hour, etc. The ROC value is used by a PLC to control the rate at which a feed is being executed e.g., feed 1000 lbs of material at 100 lb/min.

Hardy has multiple products that can be installed to manage ROC applications in different ways:

  1. HI1746 (PLC plug-in module, includes ROC as a standard function)
  2. HI1769 (PLC plug-in module, includes ROC as a standard function)
  3. HI1756 (PLC plug-in module, includes ROC as a standard function)
  4. HI2151/30 (instrument, includes ROC as an optional function)
  5. HI3030 (instrument, includes ROC as an optional function)
  6. HI4050 (instrument, includes ROC as an optional function)
  7. HI4060 (instrument, includes ROC as a standard function)
  8. Any Hardy PLC plug-in module or Hardy instrument IF ROC functionality is executed in a PLC