Near Field Probe Set

PS-400 Specifications

1. What frequency ranges do the probes in the PS-400 set cover and why is this range important for EMI investigation?

The PS-400 includes an H-field loop (9 kHz to 5 GHz), a broadband E-field probe (50 kHz to 5 GHz), and a fine tip E-field probe (100 kHz to 5 GHz). This wide coverage enables troubleshooting of low-frequency power noise through high-frequency digital harmonics encountered in modern embedded and RF systems.

2. How do the E-field and H-field probes differ in what they measure?

E-field probes respond primarily to voltage-driven emissions such as clock lines and logic traces. The H-field loop probe detects current-driven magnetic fields typically associated with switching regulators, power loops, and chassis leakage.

3. What equipment is typically used with PS-400 probes for visualization?

The probes connect via BNC to a spectrum analyzer or EMI receiver with 50-ohm input impedance. The analyzer is typically set to the emission frequency of interest with span and RBW matched to far-field measurements for correlation.

4. When should an amplifier such as PAP-501 or PAM-103 be used with the PS-400?

An inline preamplifier is recommended when investigating low-level emissions or when analyzer noise floor limits visibility. The PAP-501 provides 21 dB nominal gain over 10 MHz–1000 MHz and is ideal for broadband enhancement. The PAM-103 can be used when higher gain or extended low-frequency sensitivity is required. Amplifiers improve dynamic range but should be used carefully to avoid compression.

5. What is the role of the fine tip E-field probe in pinpointing EMI sources?

The fine tip probe enables localization down to individual pins or traces, including features as narrow as 3 mils. It is especially useful after the broadband probe identifies the general hot spot region.

6. Can the PS-400 set replace formal compliance measurements?

No. Near-field probing provides relative measurements used for design debugging and mitigation validation. Final compliance must be verified in accredited far-field test environments.

7. What practical setup considerations improve repeatability?

Maintain constant probe orientation, consistent spacing from the DUT, and minimal cable movement. Repeatable positioning is critical when comparing mitigation changes.

8. How does PS-400 assist in enclosure leakage detection?

The H-field loop probe can scan seams, ventilation slots, and cable entry points to detect slot antenna effects or poor bonding.

9. What EMI problem scenarios benefit most from PS-400 usage?

Clock harmonics coupling to chassis, high-speed bus radiation, impedance mismatches on signal lines, and unexpected cable emissions.

10. How can PS-400 reduce development cycle time?

By identifying dominant emission sources early in the prototype phase, costly late-stage redesigns and failed compliance tests can be avoided.

11. How should probe orientation be adjusted during experiments?

E-field probes should be oriented perpendicular to electric field lines, while H-field probes should align with magnetic flux paths for optimal coupling.

12. Are near-field measurements absolute or relative?

They are relative measurements. They are used to compare mitigation effectiveness rather than to determine regulatory compliance levels.

13. Can PS-400 help evaluate switching power supply noise?

Yes. The H-field probe is particularly effective in identifying high-current switching loops and transformer magnetic leakage.

14. What design issues can be diagnosed using PS-400 probes?

Transmission line reflections, impedance mismatch at source or load, via discontinuities, stub effects, and trace routing inefficiencies.

15. Is training required for effective use?

A working knowledge of EMI fundamentals and spectrum analyzer operation significantly improves diagnostic efficiency.