Glossary · Automation fundamentals, platforms and components
Voltage
Also known as: Electric potential difference
German: Spannung
In electrical engineering, voltage is the electric potential difference between two points, measured in volts (V). In automation, typical voltages include mains and motor supply voltages, 24 V DC control voltage and signal voltages such as 0–10 V.
- Automation components
In one sentence
Voltage is the electric potential difference between two points, in volts; automation uses mains, 24 V DC control and 0–10 V signal voltages.
Example
The machine is connected to 400 V AC three-phase, while sensors and PLC I/O run on 24 V DC from a power supply unit.
How it applies
- Engineering: Voltage levels determine insulation, clearances, protective measures and component selection. Low-voltage directive scope and protective extra-low voltage (PELV/SELV) concepts depend on voltage limits defined in the standards.
- Safety: Dangerous voltage can remain after switch-off, for example in DC link capacitors of drives. Electrical hazard instructions must state waiting times and how to verify absence of voltage.
- Documentation: State rated voltage, tolerance, frequency and number of phases on the nameplate, in the installation instructions and in circuit diagrams. Use the correct unit symbols (V, kV, V AC, V DC) consistently.
Voltage vs. current
Voltage is the driving potential difference; current is the flow of charge that results in a circuit. Analog signals can use either: 0–10 V voltage signals or 4–20 mA current signals, which are less sensitive to long cables and allow wire-break detection.