Chapter 14 Analog Device Installation and PLC Programming

1. Chapter 14Analog Device Installation and PLC Programming Analog PLC, Input Device, and Output Device Circuit Wiring • Programming for Analog Input and Output Devices • Troubleshooting PLC Analog Input Circuits • Troubleshooting PLC Analog Output Circuits

2. When controlled by a PLC, a level sensor can maintain a specific level in a tank by varying the position of the outlet valve.

3. Analog input devices (sensors) are used in a wide variety of applications.

4. The PLC signal allows the VFD to operate the fan at the speed required to maintain positive air pressure in the clean room.

5. In some applications, sensors must be protected from direct contact with the corrosive material being measured by devices such as wells.

6. Sensor installation instructions provide information on special installation procedures, hardware, and mounting.

7. The power supply for a PLC sensor may be internal (from the PLC) or external.

8. Shielded twisted pair cable reduces the harmful effects of electrical noise, but the shield and drain wire can only be terminated at the PLC end, not the sensor end.

9. A flow sensor can measure flow rate, sending a signal to the PLC to adjust the valve position to maintain the flow rate specified by the program. A VFD can be used as an intermediate device to control the speed of a motor.

10. The signal from a PLC analog output terminal can be directly sent to an actuator, or can be sent to another piece of equipment such as a VFD.

11. PLC actuators are mounted adjacent to or directly on the valve or damper they control.

12. Valve and damper specifications provide information such as the torque required by the actuator for proper operation.

13. PLC actuators require a separate power source (electrical or pneumatic) to power the actuator motor or piston, which is used to vary the position of the valve or damper.

14. A PID instruction allows a technician to access the PID Setup screen. Using this screen, the technician can optimize analog control by adjusting the numerous parameters related to the instruction.

15. Output data table files are used to monitor PLC analog output operations.

16. The analog setup dialog window of the microcontroller setup dialog box allows the technician to choose the output mode of the analog output signal, enable the analog inputs, and adjust the analog input filter settings to minimize the impact of electrical noise.

17. The voltage or input current from a sensor can be checked at the analog input terminals of the PLC.

18. To determine whether the sensor or the wiring between the PLC and the sensor is bad, the voltage or current from the sensor must be checked at the sensor.

19. The numbers in the analog input data table file must change as the sensor is actuated.

20. The output voltage or current from the PLC to the actuator can be checked at the analog output terminals of the PLC.

21. To determine whether the actuator or the wiring between the PLC and the actuator is bad, the voltage or current can be checked at the actuator.

22. The numbers in the analog output data table file should change as the sensor associated with the analog output is actuated.