Glossary · Process instrumentation and analytical measurement
Isolation amplifier
Also known as: Isolating amplifier, Galvanic isolator
German: Trennverstärker
In instrumentation, an isolation amplifier is a device that transfers an analog signal from input to output while galvanically isolating the two circuits, often also converting or amplifying the signal and, in explosion-protected versions, forming the associated apparatus of an intrinsically safe circuit.
- Process instrumentation
In one sentence
An isolation amplifier transfers an analog signal while galvanically isolating input and output, preventing ground loops and interference.
Example
An isolation amplifier between a thermocouple transmitter and the PLC input removes an offset caused by a ground loop between two buildings.
How it applies
- Engineering: Galvanic isolation breaks ground loops, protects inputs against overvoltage and allows signals between different potentials. Isolation voltage, accuracy and response time are the key specifications.
- Explosion protection: Isolation amplifiers with Ex i input act as associated apparatus and supply field devices in hazardous areas. Their certificate defines the permissible connections.
- Commissioning: Check that input and output types and ranges match the connected devices and that the supply is correct.
- Documentation: Show isolation amplifiers in loop diagrams, with their function and, for Ex versions, their certificate data. They are easily forgotten in troubleshooting.
Isolation amplifier vs. signal isolator
The terms overlap strongly. Isolation amplifier emphasizes signal transfer, possibly with amplification; Signal isolator emphasizes the isolation function. Catalogs often use both for the same device.