Weighing Applications

Weight Measurement

Typically deployed in all four manufacturing areas in a plant: STOCK (inventory management); MAKE (batching and blending); PACK (filling and dispensing); SHIP (product inspection). Used when is it important to be able to determine the weight in a vessel to a “high accuracy” e.g., 0.02% to 2% of full-scale capacity.

Material Feed Control by Weight (GIW/LIW)

Typically deployed in two manufacturing areas: MAKE (batching and blending) or PACK (filling and dispensing). It may be used in either "gain in weight" or "loss in weight" applications, usually abbreviated to GIW and LIW.

In this application, the goal is to feed the exact amount of material required, in the minimum amount of time, every time. Consistency is key to deliver the best OEE (Operational Equipment Efficiency) possible, a measure of availability, performance, and quality. The additional benefit is accurate fills reduce giving product away or underfills, that risk regulatory non-compliance.

Material Feed Control by Rate (LOW)

Typically deployed in two manufacturing areas: MAKE (batching and blending) or PACK (dispensing). It is used in "loss of weight" applications, usually abbreviated to LOW. This terminology is used to help differentiate this application from the LIW application above. Control functionality included for this application include: a setpoint for rate control; automatic refill cycle; rate of change exception to eliminate upsets.

Product Inspection by Weight (Checkweighing)

Typically deployed in two manufacturing areas: PACK (portioning/grading) and SHIP (product inspection). Checkweighers can monitor the weight of:

• a piece (e.g., can/bottle/pouch etc.)
• a case of pieces
• a pallet of cases.

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.

Piece Count

Typically deployed in two manufacturing areas: STOCK (inventory management) and PACK (filling and dispensing). Used to automatically validate goods being received from a vendor e.g., that 1000 bolts are in a carton, or that there are 50 piston heads in a crate. Piece count is also used to automatically dispense, for example 150 plastic spoons into a carton.

Level Measurement by Weight

Typically deployed in one manufacturing area: STOCK (inventory management). Predominately used where a “low accuracy” level indication will do e.g., +- 2% to 10% of full capacity. In these applications weight can be used to calculate the level (height) of a material in a silo, vessel, or tank. The level is expressed as a percentage e.g., 0% (empty), 36%, 50% (half full), 71% and 100% (full). Often high and low alarms are added to announce the silo level is approaching a desired max desired inventory level, or min inventory level that indicates it is time to reorder material for this silo.