PLC Analog INPUT OUTPUT

Question 1

What are commonly used analog inputs to PLC’s?

Answer 1

Voltage signals (v) and currents (mA)

Question 2

How are signals dealt with

Answer 2

PLC’s use IOC modules to deal with analogue signals using transmitter

Question 3

What are the differences between current mode and voltage mode

Answer 3

Mode Analog Inputs are affected by cross noise interference from devices.

Current mode is better for signals that need to travel considerable distance.

Difference is current mode is a voltage mode with high resistance.

Question 4

What commonly used analogue device input from current mode and how much amps are used?

Answer 4

Powered by 4- 20 miliamp signal

Question 5

Give examples of temperature device for PLC and characteristics

Answer 5

Thermocouple and RTD
Thermocouple is old temperature measurement device which has a small signal range . It needs right type of wiring for carrying signal. It needs appropriate shielding and routed away from from high voltage. It needs cold junction compensation. Type J thermocouple is common type.

RTD is a more modern temperature device and can handle high temperatures. Resistance of devices change with temperature. It comes with three or four wiring configurations.

Question 6

What is MQTT?

Answer 6

Message queuing telemitory transfer - Function extension acting as Message broker used for communicating between office applications to industrial/factory systems.