Witnessing EMI Testing Properly Adds Value

Witnessing EMI Testing

Witnessing EMI/EMC testing is a complex task.  Conducting this task properly can add value to your product development efforts.  More often than not products fail their initial testing.  Because of this, iterations of redesign and retest are required.  This can result in budgetary and scheduling issues for your design team and delay getting your product to market.

What is EMI/EMC Testing?

Let’s start by defining what testing is.  The word test has many definitions.  The definition critical for our subject is “a procedure for critical evaluation“.  There is significantly more going on than the pass/fail exams we took in college.  This process verifies that the product will meet design specification when operated in its intended environment and validate that it meets or exceeds customer requirements. 

When products experience issues in the field they can interfere with other equipment in their environment.  They can also be susceptible to radio frequencies that result in unexpected behaviors of the product.  These issues can result in property damage, injury, and death.  They can also result in product recalls, product liability cases, and fines.  Therefore properly conducted testing is of great importance.

Have a Plan – A Test Plan

The first step is to understand what testing is to be accomplished.  This will require reading and comprehending the standard and its requirements.  Once that has been done creating a test plan is essential.  This is because it is important to clearly communicate to lab personnel important information that is specific to your equipment.  This would include:

Testing to be Performed

This not only would include what testing is to be performed but document required pass/fail criteria.  This is because many standards will have different requirements for various classifications of equipment. 

Description of Equipment to be Tested

This should include a general description including model, serial number, and version numbers for hardware and software.  It should also include power requirements and overall size of the equipment.

Modes of Operation

This section should define all operational modes of the equipment, control settings, required interconnections.  It should also include any grounding or load requirements.

Performance Checks

Remember that we are trying to verify and validate the performance of the product.  Testing the equipment in an idle mode will not accomplish this goal.  Therefore it is important to provide simulation equipment to exercise the test item during both emissions and susceptibility procedures.

Susceptibility Criteria

It is important to define what your equipment’s acceptable level of operation when conducting susceptibility testing.  Often requirements for classes of equipment are established in the test standard.  This will inform the lab what the pass/fail criteria for the test will be.

Electrostatic Discharge Schedules

It is a good idea to document test points for Electrostatic Discharge (ESD) testing.  The documentation should include points where likely discharges from human contact would occur.  This documentation instructs the lab personnel to conduct a test that returns valid data.

Witnessing EMI Testing – Do the Work

Sitting in the waiting room of a lab plinking on a laptop is not providing any value to test activities.  A test witness should go to the lab prepared to work.  Communicate with the lab personnel what is to be done and make sure they are clear about the details.  Set up the test equipment and ensure it is operating correctly.  Place the equipment into a required mode of operation and check to see that simulation equipment, monitoring equipment and loads are behaving properly.  It is important to assist in monitoring the test item to capture any intermittent failures when performing susceptibility testing.

Data Gathering and Troubleshooting

The real challenge when witnessing EMI/EMC testing is when a test fails.  Time management is critical.  Selecting the best avenue for isolating and analyzing the cause of the failure can best utilize that time.  While you may not be able to “solve” the problem at the lab, you can identify causes of the failure.  You can also identify mitigation techniques that should be considered for design modification.  All of this activity should be documented and included in a final report.

CVG Strategy

It can be a challenge to perform witnessing of EMI/EMC testing in the new reality of Covid-19.  Travel of essential personnel to test facilities is often not an option.  CVG Strategy test and evaluation consultants are ready to help.  We are partnered with local labs to provide test program management and test witnessing services.  We offer a variety of test documentation products including our EZ-Test Plan Templates.

Our subject matter experts have decades of experience in aerospace, automotive, defense, and commercial applications.  They can help you with design issues by performing product evaluations and susceptibility analysis.  Contact Us today to see how we can help.

Jamie Hamilton

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