Indirect Lightning Testing and the Influence of Couplers
It is possible to design a test system (generator / coupler combination) that will deliver both voltage and
current impulses, into a cable bundle, with a fixed impedance. These are known as hybrid circuits and are in fact utilized by some OEMs in indirect lightning requirements. The advantage of hybrid test systems is that they are independent of cable (load) impedance being defined into the extreme conditions of open and short circuit.
Couplers are a vital element in any indirect lightning test system. Varying the turns ratio on a coupler can be used to either increase secondary CURRENT into the EUT or, by Increasing secondary turns (for cable
bundle tests this can be the number of cable loops in the coupler) increasing the VOLTAGE into the EUT.
Hybrid systems eliminate calibration and cable bundle issues but are costly, large and very heavy making
it difficult to comply with the requirements of DO-160 either in terms of cable length or test setup.
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