Spectrum-Analyser Setup
CANBench TrueZ v1.1 — Fabricated prototype, sole built unit. V1.1 is electrically identical to the V1.2 schematic refresh but predates the InvenTree symbol-library migration; the schematic component metadata reflects legacy SCADYS naming. Testing and bench validation reference this V1.1 hardware.
Other versions: v1.2 — schematic refresh (next version)
The TrueZ presents a 50 Ω source at each output across the conducted-emissions band. Any analyser that covers the band and accepts a 50 Ω input will work. The analyser configuration is the same as for the CANBench Duo — only the impedance requirement is stricter.
The faceplate measurement conditions — CM-25Ω (49.9 Ω shunt in parallel with the analyser's 50 Ω) and DM-100Ω (49.9 Ω series with the analyser's 50 Ω) — are defined for a 50 Ω analyser input. A high-impedance oscilloscope input, or an analyser switched to 1 MΩ, changes the loading and invalidates the calibration. Confirm 50 Ω before measuring.
General configuration (any analyser)
| Parameter | Value |
|---|---|
| Input impedance | 50 Ω (mandatory) |
| Start frequency | 150 kHz (CISPR 25 low edge) |
| Stop frequency | 30 MHz for routine work; 108 MHz for the full CISPR 25 band |
| Detector | Peak (Max-hold for time-varying disturbances) |
| Reference level | Adjust per analyser; typical −60 dBm to −20 dBm |
| Attenuation | 10 dB starting point |
| RBW | 9 kHz (150 kHz – 30 MHz) / 120 kHz (30 – 108 MHz) for CISPR-aligned work; otherwise auto |
| LNA / preamp | OFF for normal signal levels |
Low-frequency correction
The TC1-1-13M+ transformers droop below ≈ 0.5 MHz, so readings at the bottom of the CISPR conducted band (150 kHz upward) read low until corrected. Apply the TrueZ low-end correction curve in post-processing. Note this curve is currently a first-order simulated model — the golden-prototype VNA measurement that will replace it is still outstanding (see Tasks), so treat low-band absolute levels as provisional. Above ~1 MHz the transformer response is flat and no correction is needed for relative measurements.
tinySA ULTRA (recommended)
The tinySA ULTRA is the analyser SCADYS uses for engineering validation. Use the General configuration above; set the input to 50 Ω, Peak detector, LNA off, 10 dB attenuation as a starting point, and extend the stop frequency to 108 MHz for the full band.
See Measurement Procedure for the sweep workflow.