PLC - Programmable Logic Controller

Que: What is the difference between analogue input and analogue output?

Ans:

• Analogue input: which gives continuously signal from field to plc.

Examples: Level sensor, pressure sensor, temperature sensor (RTD, thermocouple etc)

• Analogue output: giving continuous command from plc to field.

Examples: VFD

Que: What is the difference between digital input and digital output?

• Digital input: means giving feedback to PLC.

Examples: feedback about status of the motor is on or off or trip in condition.

On/off, trip, level switch, pressure switch, emergency stop, hooter accept push button, phase failure relay trip feedback etc.

• Digital output: means giving command to start from the PLC.

Examples: giving command to start or stop the motor.

Motor, valves, hooter etc .

Que: What is the meaning of analogue Signal?

Ans: Analogue means continuous signal.

4-20 mA, 0-10vdc, 0-5vdc

Examples: VFD to control the speed of motor, Level sensor, pressure sensor, temperature sensor (RTD, thermocouple etc)

Que: What is the meaning of Digital Signal?

Ans: Digital means either 0 or 1, on/off, yes/no.

Examples: Either start or stop the motor,

level switch, pressure switch, valves etc.