Zener Barrier vs Galvanic Isolator
Side by side comparison: how they work, where each fits, and which to choose.
Quick answer: Zener barriers are cheap and simple but need a high integrity IS earth; galvanic isolators need power but no IS earth, and break ground loops.
Zener Barrier vs Galvanic Isolator: Comparison Table
| Aspect | Zener Barrier | Galvanic Isolator |
|---|---|---|
| Isolation | None | Galvanic |
| IS earth | Required, low resistance (less than 1 Ω) | Not required |
| Power supply | Not needed | Needed |
| Ground loops | Possible | Prevented |
| Signal accuracy | Voltage drop across barrier | Small conversion error |
| Cost | Lower | Higher |
Choose Zener Barrier when
- Simple loops where a reliable IS earth exists
Choose Galvanic Isolator when
- Most new installations, grounded sensors, long cables
Key Differences Explained
Both limit energy into the hazardous area so the field circuit is intrinsically safe. Zener barriers divert fault energy to earth, so the earth is part of the safety.
Isolators transfer the signal across a transformer or optocoupler, so the field side floats.
Related Glossary Terms
Free Calculators
Free Tools
Frequently Asked Questions
What is the difference between Zener Barrier and Galvanic Isolator?
Zener barriers are cheap and simple but need a high integrity IS earth; galvanic isolators need power but no IS earth, and break ground loops.
Can I use a barrier without an IS earth?
No, the earth is essential for safety.
Do isolators pass HART?
Many do; check the data sheet.
Which is more common today?
Isolators.
Learn more on the blog
Hazardous area classification zones
A practical guide on instrumentationblog.in that goes deeper into this topic with field examples.
Read Full ArticleMore Comparisons
All comparisons · Instrumentation glossary