Emissions or immunity – which do I need?
Both terms describe EMC, but from opposite directions. Which measurement you need can usually be read off the symptom you are seeing.
Short answer
Radiated emissions measure what your product puts out – measured in the fully anechoic chamber in Harbke. Immunity testing checks what your product can withstand – tested in the shielded chamber in Meine. If your device disturbs others, it is about emissions. If your device gets disturbed, it is about immunity.
The difference in one sentence
A device is electromagnetically compatible if it works in its environment without unduly disturbing others – and without being unduly disturbed itself. The two measurement directions follow from those two halves of the sentence.
They are measured separately because they need different instruments and different environments: emissions require a low-reflection environment, immunity a shielded environment in which disturbances are deliberately coupled in.
Which symptoms point to what
Find the observation that comes closest to your situation.
- “Another device nearby is disturbed as soon as my product runs.”Radiated emissions
- “An external test showed exceeded limits.”Radiated emissions
- “My device drops out when a machine next door switches.”Immunity testing
- “Touching the enclosure causes resets.”Immunity testing
- “Communication breaks down in certain environments.”Immunity testing
- “All I know is that EMC will become a topic – nothing more yet.”Consulting
The two measurements compared
Emissions
- Question
- What does my product put out?
- Test methods
- radiated and conducted
- Test environment
- selected per test method and device – Harbke or Meine
- Typical result
- Level per frequency, comparison against limits
Immunity
- Question
- What can my product withstand?
- Test methods
- radiated, conducted, ESD, surge, burst
- Test environment
- selected per test method and device – Harbke or Meine
- Typical result
- Documented behaviour per disturbance
When both make sense
For most products, requirements apply in both directions. During development, an order still pays off: measure first in the direction where a problem is suspected, or where a finding already exists.
Doing both at once makes sense if you need the complete status ahead of an external test, or if a measure affects both sides – a shield bond usually works in both directions.
If you are unsure, we settle the order beforehand in EMC consulting – which usually saves measurement time.
Decide on the right measurement together
Briefly describe what you are observing on your product – we will tell you which measurement helps.