Test Setup, Measurement & Detectors
From the seven-step measurement procedure to the four detector types and the distance a lab actually places the antenna from the EUT — this module ties the environment and equipment from Module 07 into a repeatable, animated test process, with a real EUT test setup diagram and interactive Plotly charts.
Every accredited RE test follows the same repeatable sequence, regardless of product type or standard. The steps below are shown alongside a live animation of what actually happens on the test-site turntable while each one runs.
The receiver's detector determines how it converts a raw, rapidly fluctuating RF signal into the single displayed emission level. The same noisy pulse train can produce four very different readings depending on which detector is selected — which is why standards mandate a specific detector for compliance rather than leaving it to the tester's choice.
| Detector | How It Responds | Purpose |
|---|---|---|
| Peak | Captures and holds the single highest instantaneous amplitude in the measurement window. | Fast pre-scan — always reads at or above the true compliance level, so nothing failing is ever missed. |
| Quasi-Peak | Weights repetitive pulses by how often they occur using standardized charge/discharge time constants, mimicking human annoyance perception. | CISPR compliance — the detector actually named in most commercial limit lines. |
| Average | Averages the signal envelope over the measurement time, smoothing out short transients. | Continuous / narrowband emissions such as clock harmonics. |
| RMS | Reads the true root-mean-square power of the signal over the measurement time. | Broadband measurements where total energy content matters more than any single peak. |
In the far field, radiated field strength falls off roughly as 1/d, so moving the antenna from 3 m to 10 m alone would drop the reading by about 10.5 dB even if the EUT emitted nothing differently — this is exactly why the standard specifies both a limit and a fixed measurement distance together, and why results at one distance can't be casually compared to results at another without a correction factor.
| Distance | Typical Application |
|---|---|
| 1 m | Automotive (component-level, small chamber footprint) |
| 3 m | Medical, Industrial, Consumer |
| 10 m | Large equipment, OATS (Open Area Test Site) |
Putting it all together: the EUT sits on an insulating turntable at a fixed height above the ground plane, cabled with its worst-case peripheral harness draped per the standard's cable-routing rules, while a mast-mounted antenna at the specified test distance feeds the receiver through low-loss coax and an optional LNA. This is a realistic illustration of that full chain since a licensed stock photo of a live test setup isn't available to embed here.
The measurement chain from Section 4 is built from a small, well-defined set of equipment, each piece contributing a known gain or loss that must be accounted for in the final reading.
Module 8 Quiz
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