Chapter 8

Select the true statements about a one-shot instruction.

it stays on for one scan and goes off. it is triggered by the leading-edge transition of the input signal in a SLC 500 plc.

identify the features of up-counter instruction.

its accumulative value is incremented on false to true transition of an input instruction. it is a output instruction.

the counter is reset if the reset condition is activated at the time of power restoration.

true

select the correct statements about the counting frequency of a PLC counter.

when the frequency of the input signal is higher than that of the scan timer is necessary to utilize a higher-speed counter. The maximum counting frequency of a PLC counter is limited by the scan time of the processor.

Identify the true statements about ORS instruction.

I triggers an event to occur on time. it is an input instruction.

Select the correct statement about incremental encoder.

Incremental encoder output pulses each time and only when the shaft is turned. They provide a specific number of equally spaced pulses per revolution of linear motion.

Select the true statements about the accumulated value.

It is the current count base on the number of times the rung goes from false to true. it increments with a false to true transition of the count -up counter instruction.

A CTU instruction that is reset while counter logic remains true will the result accumulate value of 1 instead of 0. Using the _____________ instruction in the counter enabling logic prevents this from happening.

ORS

Choose the counter statement about high speed counters and their instruction in a PLC

The HSC instruction is used to configure control and monitor the counters internal hardware counter. The high-speed counter operate independently of the controller scan.

identify the true statement about mechanical counters.

The actuating lever return automatically to its original position after counting. The actuating lever is moved over to count every time.

identify the true statement about the control bits in a counter file.

The count-up enable bit is true whenever the count-up counter instruction is true. The count down enable bit is true whenever the count down counter instruction is true.

which of the following statements are true of the counters in an Allen-Bradley SLC 500?

The data works share the same base address. The base address is the address of the counter.

select the correct statement about the counting frequency of a PLC counter.

The maximum counting frequency of a PLCs counter is limited by the scan of the processor. When the frequency of the input signal is higher than that of the scan time, it is necessary to utilize a high-speed counter.

In an allen-bradley SLC 500 counter file each composed of____________ words, collectively called a counter element.

Three 16-bit

identify the true statements about a one-shot instruction.

is is used to automatically clear or reset a counter. it can be triggered by a momentary pulse. it is also known as a transitional instruction.

Identify the true statements about an incremental optical encoder.

the encoder disks interrupt the light as the encoder shaft is rotated to produce the output waveform. An incremental optical encoder creates a series of square waves as its shaft is rotated.

Select the correct statement about counters.

they are dependent on external source for counting. they do not operate on an internal clock for counting.