Deck 22: Understanding Communication Networks

Question 1

Explain why it is necessary to filter analog noise.

Answer 1

When working with analog input signals it is not uncommon to have analog signals that may contain some degree of noise. The problems that this noise can cause vary, depending on the severity of the noise, and how the analog data is intended to be used. Common problems include digital displays that become hard to read, unnecessary and erratic operation of analog output devices, process errors or disturbances, etc. The solution to noisy analog input signals is to implement some kind of signal conditioning, either hardware or software based.

Question 2

The circuit in the accompanying figure is an example of a(n) ____________________ circuit.

Answer 2

push on/push off,push on push off

Question 3

Explain the operation of the circuit shown in the accompanying figure.

Answer 3

Shown in Figure 22-13 is the PLC logic for our bit array tracking system described above. We have shown the "Bit Shift Left" instruction with a file or array address of #B3:0. We have also shown the file or array address for the Photoelectric Sensor and Spray Nozzle in Figures 22-11 and 22-12 for clarity. The "Conveyor System Running" digital input in Rung 2 is there to ensure that the "Spray Nozzle" output operates only when the conveyor is moving.

Question 4

The accompanying figure shows a memory address labeled as Digital Input connected to the normally closed contact marked "Start Push Button."

Question 5

Explain the operation of the basic flip/flop circuit using the accompanying figure.

Question 6

Explain the operation of the circuit in the accompanying figure.

Question 7

A word address in PLC memory containing a decimal value being sent to a real-world output device such as a valve, variable speed drive, or panel meter is a(n) ____________________.

Question 8

A digital address in the output memory area of the PLC that a real-world device is being controlled from, such as a pilot light, motor starter, or solenoid, is referred to as Digital Memory.

Question 9

A word address in PLC memory containing a decimal value from a real-world input device such as a temperature sensor, or pressure transmitter is a(n) ____________________.

Question 10

In most cases, there is more than one solution to a problem. The right solution and subsequent logic depends on having a thorough understanding of the machine or process to be controlled.

Question 11

Explain why a PLC should know the state of an attached motor starter.

Question 12

The accompanying figure is an example of a ½ ____________________ circuit.

Question 13

The convention for programming examples in the text uses Analog Memory to refer to a word address in a user memory area of the PLC containing a decimal value from calculations or values to be stored for comparison type instructions.

Question 14

When controlling industrial motors with PLCs, it is often desirable to monitor and know when motor starters fail to operate as directed.

Question 15

The circuit in the accompanying figure is a common logic circuit called the ____________________ circuit.