Electronics Guide

Test Environment and Equipment

Radiated immunity testing requires a controlled electromagnetic environment to generate uniform, calibrated fields at the equipment under test (EUT). Several test environments are used:

Anechoic chambers: Fully or semi-anechoic chambers lined with radio frequency absorbing material create a controlled environment free from reflections and external interference. Semi-anechoic chambers have absorber on walls and ceiling with a conductive ground plane floor, providing a defined reflection condition that approximates many real installations.

Stripline and TEM cells: These guided-wave structures generate uniform fields within a defined test volume. TEM (transverse electromagnetic) cells and GTEM (gigahertz TEM) cells offer compact alternatives to anechoic chambers for smaller equipment, though they have limitations on EUT size and the frequency range for true TEM mode operation.

Reverberation chambers: Mode-stirred reverberation chambers create statistically uniform field exposure through mechanical stirring or frequency stirring. While the instantaneous field is not uniform, the statistical field distribution provides equivalent exposure over the test duration, often with more efficient power usage than anechoic testing.

The test system includes a signal generator providing the modulated RF signal, power amplifiers to achieve required field strengths, transmitting antennas appropriate for the frequency range, field monitoring sensors, and control equipment to automate the frequency sweep and field leveling.

Test Procedure

The standard test procedure involves these key steps:

Field calibration: Before testing, the field is calibrated across the test area using a calibrated field sensor. The field uniformity must meet specified criteria (typically within +6 dB to 0 dB of the target level over 75% of the uniform field area). This calibration establishes the power required at each frequency to produce the specified field strength.

EUT configuration: The equipment is set up in its normal operating configuration on a non-conductive table or ground plane as appropriate. Cables are arranged in standardized configurations to ensure reproducible coupling. The EUT should be performing a representative function that allows detection of disturbances.

Frequency sweep: The modulated RF signal sweeps across the specified frequency range, typically 80 MHz to 1 GHz for basic compliance, with extended ranges to 2.7 GHz or 6 GHz for some applications. The signal is amplitude modulated at 80% depth with a 1 kHz sine wave to simulate voice-modulated transmissions and detect both RF rectification and audio frequency demodulation.

Dwell time: At each frequency step, the field is applied for sufficient time (typically 3 seconds minimum) to observe any equipment response. Sweep rates and step sizes must allow full EUT response at each frequency.

Orientation: Testing is performed with the field in both vertical and horizontal polarization, and typically with the EUT in multiple orientations to find the most susceptible configuration.

Test Levels and Criteria

Standard test levels range from 1 V/m for light residential environments to 10 V/m or higher for industrial and automotive applications. Some specialized applications require 30 V/m or more. The test level selection depends on the intended installation environment and applicable product standards.

Performance criteria define acceptable equipment behavior:

• Criterion A: Normal performance within specification limits during and after the test. No degradation or loss of function is permitted.
• Criterion B: Temporary degradation or loss of function is permitted during the test, provided the equipment self-recovers to normal operation afterward without operator intervention or data loss.
• Criterion C: Temporary degradation is permitted during the test, with recovery possible through operator intervention (such as power cycling) or automatic reset. No hardware damage or permanent data loss should occur.

Product standards specify which performance criterion applies for each test and test level.

Design for Radiated Immunity

Achieving radiated RF immunity requires attention to several design aspects:

Enclosure shielding: Conductive enclosures attenuate field penetration, but apertures, seams, and ventilation openings limit effectiveness. Shield integrity must be maintained at the highest test frequencies, requiring careful treatment of all openings and proper bonding at seams. Conductive gaskets or finger stock may be needed at panel interfaces.

Cable entry treatment: Cables penetrating the enclosure act as antennas that couple fields into the shielded volume. Feedthrough filters, shielded connectors with 360-degree shield termination, or ferrite chokes at cable entries reduce this coupling path.

Internal circuit immunity: Even with good shielding, some field penetration occurs. Internal circuits should have adequate noise margins, proper filtering on sensitive inputs, and layout practices that minimize field coupling to critical traces. Differential signaling and balanced circuit design reduce common-mode susceptibility.

Firmware resilience: Software techniques including input filtering, plausibility checking, watchdog timers, and error recovery can help equipment maintain acceptable behavior even when some RF-induced disturbance reaches circuit nodes.

Test Rationale and Coupling Mechanisms

Cables attached to equipment can be electrically long at RF frequencies, making them efficient antennas. A 1-meter cable is approximately one-quarter wavelength at 75 MHz, approaching resonant antenna behavior. The ambient electromagnetic field induces common-mode currents on these cables, which then enter the equipment as conducted disturbances.

Rather than attempting to control the radiated field coupled to cables (which would require an extremely large anechoic chamber), conducted immunity testing directly injects a known RF signal onto cables. The test specifies the common-mode voltage or current that would result from field coupling, allowing reproducible testing in simpler environments.

Coupling Methods

Three coupling methods inject the RF signal onto cables:

Coupling-decoupling networks (CDN): These networks insert the RF test signal onto the cable while blocking RF from reaching auxiliary equipment at the far end. Different CDN types address various cable configurations: CDN-M types for power mains cables, CDN-S types for shielded signal cables, and CDN-AF types for coaxial ports. CDNs provide the most defined and reproducible injection but require a specific network for each cable type and connector.

Electromagnetic clamp: The EM clamp is a current transformer that couples RF current onto a cable without requiring galvanic connection. It can inject onto cables without disconnection but has frequency-dependent coupling efficiency and is limited to cables that physically fit through the clamp aperture.

Current injection probe: Similar to the EM clamp, the current injection probe couples RF magnetically to the cable. Used with calibration procedures to establish the injected current level, it offers flexibility for various cable configurations but requires careful calibration.

Test Setup and Procedure

The test setup includes a signal generator, RF amplifier, coupling device, and auxiliary equipment or terminations at cable far ends. The EUT is placed on a ground reference plane with cables routed in standardized configurations.

Before testing, the injection level is calibrated. For CDN injection, the common-mode voltage is set using the CDN's calibration port. For clamp or probe injection, the induced current or voltage is measured and adjusted to achieve the specified level.

The test applies an 80% amplitude-modulated signal (1 kHz modulation) across the frequency range, typically 150 kHz to 80 MHz, though some product standards extend this range. The signal is applied to each cable in turn while monitoring EUT performance. Dwell time at each frequency step must allow full EUT response.

Test Levels

Test levels are specified as RF voltage (EMF) into 150 ohms. Common levels include:

• Level 1 (1 V): Light residential and commercial environments
• Level 2 (3 V): Typical residential, commercial, and light industrial
• Level 3 (10 V): Industrial environments with close RF sources
• Level 4 (30 V) and above: Severe industrial or environments with high-power RF

Performance criteria follow the same A, B, C classification as radiated testing.

Design Considerations

Protection against conducted RF disturbances focuses on preventing RF energy from reaching sensitive circuits:

Input filtering: Filters on all external interfaces should attenuate RF signals before they reach active circuits. The filter cutoff frequency should be well below the lowest test frequency (150 kHz) for digital interfaces, or include appropriate RF bypassing for interfaces that must pass lower-frequency signals.

Common-mode rejection: Since conducted RF appears as common-mode current, differential interfaces with good common-mode rejection inherently reduce susceptibility. Common-mode chokes on cables are effective at presenting high impedance to the injected common-mode signals.

Grounding impedance: The path from filter capacitors to chassis ground should have low impedance at RF frequencies. Short, wide connections to the ground plane or chassis minimize inductance that would otherwise reduce filter effectiveness.

PCB layout: Keeping filter components close to connectors, maintaining solid ground planes under filter circuits, and avoiding routing sensitive traces near cable entry points all contribute to conducted immunity.

ESD Phenomena

Static charge accumulates through triboelectric effects when dissimilar materials contact and separate. Human body charging is common: walking across carpet can generate body potentials exceeding 15 kV in dry conditions. When a charged person touches electronic equipment, the accumulated charge discharges rapidly, creating the ESD event.

The discharge waveform has two components: an initial fast spike with sub-nanosecond rise time representing the discharge of the hand capacitance, followed by a slower component representing the discharge of the body and clothing capacitance through the hand and arc. The standard ESD waveform specifies a rise time of 0.7 to 1 ns, with peak current proportional to test voltage.

Test Equipment

ESD testing uses a specialized generator that simulates human body discharge characteristics. The generator includes:

Charge storage capacitor: A 150 pF capacitor representing the human body capacitance stores the charge to be discharged.

Discharge resistor: A 330 ohm resistor in series with the capacitor represents the body resistance and shapes the current waveform.

Discharge electrode: Interchangeable tips allow contact or air discharge testing. The contact tip is rounded (8 mm radius) for consistent contact discharge. The air discharge tip is pointed to promote arc initiation at specified voltages.

The generator is calibrated by measuring the discharge current into a defined target, verifying the waveform meets standard specifications for rise time and peak current.

Test Methods

Two discharge methods are specified:

Contact discharge: The electrode touches the EUT surface before the generator is triggered. This method provides reproducible discharge location and timing, preferred where metal surfaces are accessible. The discharge occurs at the moment of relay closure within the generator.

Air discharge: The charged electrode approaches the EUT until the air gap breaks down and an arc forms. This method is used for surfaces that are not conductive or where contact discharge is not practical. Air discharge is less reproducible due to variability in arc formation, but represents more realistic discharge scenarios for user-accessible surfaces.

Test points include user-accessible surfaces, connector shells, ventilation openings, and coupling planes. Direct discharges apply to surfaces users might touch. Indirect discharge applies to nearby horizontal and vertical coupling planes, simulating discharges to adjacent objects that disturb equipment through field coupling.

Test Levels and Procedure

Standard test levels range from 2 kV to 15 kV or higher:

• Level 1: 2 kV contact, 2 kV air
• Level 2: 4 kV contact, 4 kV air
• Level 3: 6 kV contact, 8 kV air
• Level 4: 8 kV contact, 15 kV air

At each test point, multiple discharges are applied (typically 10 single discharges at each polarity). A minimum 1-second interval between discharges allows EUT recovery. The EUT is monitored for malfunction, with any effects noted and classified according to performance criteria.

ESD Protection Design

Effective ESD protection requires a defense-in-depth approach:

Personnel discharge paths: Providing designated discharge points and ensuring chassis grounding allows charge to dissipate without entering sensitive circuits. User-accessible surfaces should either be insulating (preventing discharge) or connected to chassis ground through controlled impedance.

Transient voltage suppression: TVS diodes, varistors, or specialized ESD protection devices on external interfaces clamp transient voltages to safe levels before they reach sensitive components. Device selection must consider peak current handling, clamping voltage, and capacitance.

Enclosure integrity: Keeping the ESD pulse outside the enclosure prevents field coupling to internal circuits. This requires continuous shielding around openings, conductive gaskets at seams, and proper grounding of cable shields at the point of entry.

Circuit layout: Sensitive traces should not run near enclosure edges, ventilation openings, or other points where ESD fields can couple. Ground plane integrity under sensitive circuits provides field shielding. Series resistance in signal paths can limit current during ESD events.

Component selection: Input/output devices should have adequate ESD tolerance. Human body model (HBM) and charged device model (CDM) ratings indicate component-level ESD robustness. Additional protection may be needed for components with low inherent tolerance.

Transient Characteristics

EFT pulses simulate contact bounce and arc phenomena during switching. Each pulse has a very fast rise time (approximately 5 ns) and relatively short duration (approximately 50 ns), with energy content low enough that the transients typically cause upset rather than damage. The pulses occur in bursts lasting 15 ms with burst repetition at 300 ms intervals.

The standard waveform is defined in terms of front time (5 ns plus or minus 30%) and pulse duration (50 ns plus or minus 30%). Peak voltage varies with test level, from 0.5 kV to 4 kV or higher. The burst contains approximately 75 pulses at the 5/50 ns waveform.

Test Equipment and Setup

EFT testing uses a specialized generator that produces the defined burst waveform. The generator includes a charging circuit, switching element (typically a spark gap or fast semiconductor), pulse-shaping network, and output coupling networks.

Coupling to the EUT depends on the cable type:

Power line coupling: For AC/DC power cables, a dedicated coupling network injects the burst onto power conductors while protecting the power source. The coupling network presents defined impedance characteristics to shape the delivered transient.

Signal line coupling: For I/O and communication cables, a capacitive coupling clamp surrounds the cable bundle. The clamp couples the transient capacitively to all conductors within the clamp aperture without galvanic connection.

Test Procedure

The test applies bursts to power supply cables using the coupling network, and to I/O cables using the capacitive clamp. Testing is performed at both positive and negative polarity. The burst is applied for at least 1 minute on each cable and polarity combination.

During testing, the EUT performs representative functions while being monitored for malfunction. The fast pulse repetition rate (5 kHz within bursts) can accumulate energy in circuits without fast recovery, while the fast rise time creates broadband spectral content that couples through various paths.

Test Levels

Standard test levels specify peak open-circuit voltage:

• Level 1 (0.5 kV): Well-protected residential and commercial
• Level 2 (1 kV): Typical commercial and light industrial
• Level 3 (2 kV): Industrial environments
• Level 4 (4 kV): Severe industrial environments

Power port levels are typically higher than signal port levels in product standards.

Protection Against EFT

EFT protection focuses on preventing the fast transients from disturbing circuit operation:

Input filtering: Low-pass filters on power and signal inputs attenuate the high-frequency content of EFT pulses. Effective filtering requires capacitors with low equivalent series inductance (ESL) to maintain low impedance at the high frequencies present in 5 ns rise time transients.

Transient suppression: While EFT energy is relatively low, transient suppressors can help clamp voltage levels. Fast-responding devices like TVS diodes are appropriate; slow devices like MOVs may not respond quickly enough to the fast edge.

Ground plane integrity: The capacitive coupling of EFT pulses makes ground plane quality critical. Interrupted ground planes can develop transient voltage differences between sections during EFT, disturbing circuits spanning the interruption.

Decoupling: Adequate high-frequency decoupling on power supply rails prevents EFT energy that reaches the power distribution from disturbing circuits. Multiple decoupling capacitor values address the broad spectral content.

Surge Phenomena

Two primary sources create surge transients on equipment ports:

Lightning effects: Direct lightning strikes are rare but devastating. More common are indirect effects: lightning current flowing in ground systems raises local ground potential relative to distant grounds, and electromagnetic fields from lightning induce voltages in nearby cables. These indirect effects create transients of kilovolts with microsecond rise times.

Power switching: Switching of utility power factor correction capacitors, fault clearing by circuit breakers, and operation of heavy industrial loads create transients that propagate through power distribution networks. While lower amplitude than lightning-induced transients, these switching surges are more frequent.

Test Waveforms

The standard specifies two waveforms representing different surge source characteristics:

1.2/50 microsecond voltage waveform: This waveform has a 1.2 microsecond front time (10% to 90% rise) and 50 microsecond duration (time to 50% of peak on decay). It represents the open-circuit voltage of a surge source, used for high-impedance circuits.

8/20 microsecond current waveform: This waveform has an 8 microsecond front time and 20 microsecond duration. It represents the short-circuit current of the surge source, relevant for low-impedance circuits that clamp the surge voltage.

A combination wave generator produces both waveforms from a single source. Applied to a high-impedance load, it delivers the 1.2/50 voltage waveform. Applied to a low impedance, it delivers the 8/20 current waveform. Real circuits experience something between these extremes.

Coupling Modes

Surge testing addresses both differential-mode and common-mode transients:

Line-to-line (differential): Surges between power conductors (line-neutral, line-line) simulate differential-mode transients from switching events. Equipment power input circuits must withstand these transients without damage.

Line-to-ground (common-mode): Surges between conductors and earth ground simulate lightning-induced ground potential differences. Common-mode surges stress insulation and can couple through parasitic capacitances into signal circuits.

Coupling networks inject the surge onto power lines while protecting the power source. External surge-limiting elements may be needed to prevent damage to coupling networks at high test levels. For signal and telecommunications ports, different coupling networks address coaxial, balanced, and unbalanced configurations.

Test Levels

Standard test levels for power ports include:

• Level 1 (0.5 kV line-to-line, 0.5 kV line-to-ground): Protected installations
• Level 2 (1 kV line-to-line, 2 kV line-to-ground): Typical commercial/industrial
• Level 3 (2 kV line-to-line, 4 kV line-to-ground): Industrial with long cable runs
• Level 4 (4 kV line-to-line, 4 kV line-to-ground): Severe environments

Signal port levels are typically lower, depending on cable exposure to lightning effects.

Surge Protection Design

Surge protection requires coordination of multiple elements:

Primary protection: High-energy surge protective devices (SPDs) at the power entrance divert the bulk of surge energy. Gas discharge tubes (GDTs) and large MOVs handle high peak currents but may not clamp voltage low enough for sensitive electronics.

Secondary protection: Downstream SPDs with faster response and lower clamping voltage protect equipment from the residual surge after primary protection operates. Coordination between protection stages prevents secondary devices from absorbing energy meant for primary protection.

Series impedance: Inductors or resistors between protection stages limit the surge current seen by downstream protection, improving coordination and extending device life.

Circuit protection: At the equipment input, TVS diodes or small MOVs provide final protection with clamping voltages compatible with circuit withstand ratings. These devices must handle the let-through voltage and current from upstream protection.

Insulation coordination: For common-mode surges, creepage and clearance distances in circuit layout must withstand the surge voltage without breakdown. This is especially critical for isolation boundaries in power supplies.

Sources of Power Frequency Fields

Significant power frequency magnetic fields arise from:

• Power transformers, especially during inrush and fault conditions
• Heavy current bus bars and cables in industrial installations
• Motors and generators during starting or under fault
• Switchgear and circuit breakers during operation
• Welding equipment and induction heating systems

Field strengths vary widely. Near a power transformer, steady-state fields might reach tens of A/m, while fault conditions can create transient fields of hundreds of A/m. Short-duration high-amplitude fields simulate these fault transients.

Test Equipment and Procedure

Testing uses an induction coil to generate a known magnetic field strength in the test area. The coil is driven by a power amplifier at 50 or 60 Hz. Field uniformity over the EUT volume must be verified.

Two test modes address continuous and transient exposures:

Continuous field: A steady-state field at the specified level (typically 1 to 100 A/m) is applied while monitoring EUT operation. Test duration is sufficient to observe any interference with equipment function.

Short-duration field: A higher field level (typically 10x to 100x the continuous level) is applied for 1 to 3 seconds to simulate fault conditions. This tests the equipment's ability to withstand or recover from brief high-field events.

The EUT is positioned in various orientations to find the most susceptible alignment relative to the applied field.

Design for Magnetic Field Immunity

Equipment susceptible to power frequency magnetic fields can be protected by:

Magnetic shielding: High-permeability materials (mu-metal, permalloy) surrounding sensitive components attenuate low-frequency magnetic fields. Multiple shield layers may be needed for high attenuation. Shielding effectiveness at power frequency is much lower than at RF frequencies.

Circuit orientation: Minimizing loop areas perpendicular to expected field directions reduces induced voltage. Sensitive circuits should be oriented to minimize magnetic coupling from likely field sources.

Twisted pairs: For circuits extended over space, twisting conductors so induced voltages cancel between successive twists reduces net pickup. Tight, uniform twist is most effective.

Balanced circuits: Differential input circuits reject common-mode signals induced equally in both inputs. Combined with twisted pair wiring, balanced circuits provide excellent magnetic field immunity.

Power Quality Phenomena

Several phenomena cause voltage dips and interruptions:

Voltage dips (sags): Temporary voltage reductions to 10-90% of nominal, typically lasting from half a cycle to several seconds. Common causes include motor starting, transformer energization, and faults on adjacent feeders that depress voltage system-wide before protective devices isolate the fault.

Short interruptions: Complete loss of voltage for durations up to 3 minutes, typically caused by automatic recloser operation, fast transfer switching, or brief faults. Equipment must either ride through these events or restart safely.

Voltage variations: Slower changes in steady-state voltage due to changing loads on the distribution system. Equipment must operate satisfactorily across the expected voltage range.

Test Equipment

Testing uses programmable AC or DC sources that can produce controlled voltage dips and interruptions synchronized to the power frequency (for AC). The test generator must maintain waveform quality during transitions and provide repeatable dip depth and duration.

Common test generator types include:

• Amplifier-based sources providing fully controllable arbitrary waveforms
• Transformer-based switching systems that create dips by switching between voltage taps
• Impedance-based systems that insert series impedance to create voltage drops

Test Parameters

Key test parameters include:

Dip depth: The residual voltage during the dip, expressed as a percentage of nominal voltage. Standard test levels include 0% (complete interruption), 40%, 70%, and 80% of nominal.

Duration: The time from dip initiation to recovery. Standard durations range from 0.5 cycles (approximately 10 ms at 50 Hz) to 5 seconds or longer for interruption testing.

Phase angle: For AC systems, the point in the voltage waveform at which the dip begins and ends affects equipment response. Testing at 0 degrees (voltage zero crossing) and 90 degrees (voltage peak) brackets likely behavior.

Repetition: Multiple dips or interruptions may be applied to test cumulative effects and recovery time requirements.

Performance Criteria

Equipment behavior during and after dips/interruptions is evaluated against performance criteria:

Class 1 (Criterion A): Normal operation maintained throughout; no degradation permitted.

Class 2 (Criterion B): Temporary degradation during the event, with automatic recovery and no data loss.

Class 3 (Criterion C): Temporary loss of function requiring operator intervention or automatic restart, with no hardware damage.

The appropriate class depends on the application. Process control equipment might require Class 1 for short dips to maintain continuous operation, while consumer electronics might accept Class 2 or 3 behavior.

Design for Voltage Immunity

Equipment immunity to voltage dips and interruptions involves:

Energy storage: Power supply capacitors, batteries, or supercapacitors provide hold-up energy during brief interruptions. The energy storage must bridge the specified interruption duration while maintaining adequate voltage to power supply outputs.

Wide input range: Power supplies designed for wide input voltage ranges naturally ride through voltage dips without loss of output. Universal input supplies (85-264 VAC) typically perform well during dip testing.

Undervoltage detection: Controlled shutdown when voltage drops below sustainable levels prevents unpredictable behavior. Orderly shutdown can save critical data and prepare for restart.

Restart sequencing: Safe automatic restart after interruptions ensures equipment returns to a known state. Restart delays may be needed to allow power system recovery before drawing significant current.

Oscillatory Transient Phenomena

Switching operations in substations generate high-frequency oscillating transients as distributed capacitances and inductances in the installation resonate. Gas-insulated switchgear (GIS) produces particularly fast oscillations due to the compact geometry and low losses. These oscillations can reach peak voltages of several kilovolts with frequencies from 100 kHz to over 100 MHz.

The transients couple to nearby control cables through capacitive and inductive mechanisms. Cable shields reduce but do not eliminate coupling. Secondary equipment and control systems connected to these cables must withstand the conducted oscillatory transients.

Test Waveforms

The standard defines two primary waveforms:

100 kHz damped oscillatory wave: Represents transients from air-insulated switchgear and general substation switching. The waveform has a 1 MHz frequency during the rising edge, decaying to 100 kHz oscillation.

1 MHz damped oscillatory wave: Represents faster transients from gas-insulated switchgear and compact installations. Both waveforms are damped with defined decay characteristics.

The test applies both common-mode (all lines to ground) and differential-mode (between lines) transients. Test levels range from 0.5 kV to 4 kV peak, depending on installation category.

Design Implications

Protection against damped oscillatory transients requires:

• Transient protection devices capable of responding to the oscillation frequency
• High-frequency filtering to attenuate the oscillatory components
• Cable shielding with proper 360-degree termination
• Circuit immunity to repetitive transients during the oscillation

Ring Wave Characteristics

The standard 0.5 microsecond/100 kHz ring wave has:

• Rise time of approximately 0.5 microseconds to peak
• Oscillation frequency of approximately 100 kHz
• Decay to 50% in approximately 8-10 cycles

This waveform represents the residual ringing on power circuits after switching events. The energy content is moderate, typically less than surge waveforms but more than EFT bursts. The 100 kHz frequency content can couple through power supply filters more effectively than higher-frequency EFT transients.

Test Application

Ring wave testing applies the transient to power input ports through coupling networks. Test levels typically range from 0.5 kV to 6 kV peak, applied at various phase angles relative to the AC power frequency. Both common-mode and differential-mode application may be specified.

The ring wave's intermediate frequency (between EFT and surge) tests power supply filter effectiveness in a frequency range where filter capacitor ESL becomes significant but filters have not yet reached full attenuation.

Protection Considerations

Ring wave protection combines elements of EFT and surge protection:

• MOVs or TVS diodes for voltage clamping (response fast enough for the 0.5 microsecond rise)
• Filter capacitors effective at 100 kHz (requiring attention to ESL)
• Series inductance to limit current through protection devices during the oscillation

Laboratory Equipment

A comprehensive immunity test laboratory requires:

• Shielded rooms or anechoic chambers for radiated immunity testing
• RF signal generators and power amplifiers spanning required frequency ranges
• Antennas for various frequency bands and both polarizations
• ESD simulators calibrated to standard waveforms
• Surge and EFT generators with appropriate coupling networks
• Programmable AC/DC sources for voltage dip testing
• Field generating coils for magnetic field immunity
• Calibration equipment and reference instrumentation

Laboratory Accreditation

For regulatory compliance, testing should be performed by accredited laboratories. ISO/IEC 17025 accreditation demonstrates laboratory competence and quality management. Accreditation scope should cover the specific tests required for the product under evaluation.

Pre-Compliance Testing

Development testing often uses simplified setups to identify immunity weaknesses before formal compliance testing. Pre-compliance approaches may include:

• Open-area or unshielded radiated testing (results influenced by ambient RF)
• Manual ESD testing to identify susceptible points
• Simplified transient generators to verify protection circuit operation

Pre-compliance testing helps iterate design improvements efficiently before committing to formal laboratory time.

Test Plan Development

Before testing, develop a test plan that specifies:

• Applicable standards and test levels
• EUT operating modes and functions to be monitored
• Test points and cable configurations
• Pass/fail criteria for each test
• Sequence of tests and any required conditioning

Test Documentation

Document test results including:

• Equipment and calibration status
• Test setup photographs and configuration details
• Applied test levels and frequencies
• EUT behavior observations at each test condition
• Any failures or anomalies with detailed description
• Conclusions regarding compliance with requirements