Digital vs analog signals


Digital input and output signals

Digital signals are made out off bits. A bit can be 0 or 1.

The most easy way to start understanding is looking at a normal lamp. You can turn the light on with the switch and off. The switch sends power to the lamp and lamp will go on. When you turn the switch off its stops sending power and the lamp will go off.

When pressing a button in the PLCtrainingKIT the button sent a high signal to the PLC. This signal is high 24 volts. When you stop pressing the button the signal will go low and the PLC will see the 0 volts.

In the graph on the left we see a digital signal. The signal is low (0 volts) after 4 seconds the signal is high (24 volts). At 7 secondes the button is release and the signal is low again.

Digitale output signals work the same. Instead of reading the switch the PLC is become the switch. So the PLC can sent high or low to a lamp, motor, driver or heater.

Analog input signals

With analog input signals the PLC can read temperature sensors, distance, speeds or any other thing what needs more information then high 24 volts or low 0 volts. In the PLCtrainingKIT we use the 2 analog inputs to read the tank level and temperature. In the elevator scenario we use the analog input for the position of the elevator and the workload (weight).

To understand how it work we will give you an example. The tank can take 1000 Liter and is 10 meter high. That means every 1 meter is 100 liters. Are PLC can read 0 to 10 volts. If we only had 1 bit. Mean the option we have is 1 or 0. S

Barrier outputs
schuin aanzicht gesloten klein
Tank analog

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