Copyright Goodheart-Willcox Co., Inc. 188 C H A P T E R 9 Marcin Balcerzak/Shutterstock.com Chapter Outline 9.1 PLC Counter Instructions 9.2 PLC Counter Instruction Registers 9.3 PLC Count Up Instructions 9.4 PLC Count Down Instructions 9.5 Connecting PLC Counter Instructions 9.6 Cascading Counters 9.7 Creating PLC Ladder Logic Diagrams with Counters and Timers 9.8 LogixPro Simulator Examples PLC Counter Instructions Technical Terms count bit count down count up double-input counter overflow bit (OV) fl reset (RES) instruction single-input counter underflow bit (UN) fl Learning Objectives After f te r completing co mp le ti ng this t hi s chapter, ch ap te r, you y ou will w il l be be able a bl e to: to : • Use count up instructions to create PLC ladder logic diagrams. • Use count down instructions to create PLC ladder logic diagrams. • Reset counter instructions. • Connect different counter instructions and cascade counter instructions. • Use timer and counter instructions to create PLC ladder logic diagrams. Introduction S imilar to timer instructions, counters are very useful in manufacturing and industrial control systems. PLC counter instructions are used to count parts in manufacturing plants or to count events in industrial control system applications. For example, in a bottle manufacturing plant, a PLC counter instruction could be used to count the number of bottles placed in every carton. In this chapter, you will study PLC counter instructions and their use. Examples will illustrate how to use different types of counters. You will learn howtocascadecounterinstructionsinaPLCladderlogicdiagram.Also,youwill learn how to use counter instructions and timer instructions in a PLC ladder logic diagram.