By Jennifer Kitaygorsky, PhD and Anthony Supino
In DO-160 chapter 22 (and sometimes chapter 20) testing, it is often advantageous to use simulation to help understand what is happening inside of cable shields and equipment. DO-160 test waveforms that are injected onto complex cable harnesses will induce currents and voltages on the pins at equipment interfaces. EMA3D is a useful tool in understanding what the pin levels are as a result of the transfer impedance of the cable while capturing the effects of cable shields, branches and multiple conductors.
We often find ourselves doing this type of simulation during design phases or after a test failure. The purpose is not to replace the required box testing; rather, it is to help reduce the risk of failure and to help determine the cause of failures.
This training shows a DO-160 type measurement of a 22 AWG twisted shielded pair, and compares the test results with simulation results.
This measurement is for training purposes only. In actual DO-160 testing, waveforms defined in the DO-160 document are typically used.
A double exponential current waveform resembling lightning component A, but with 400 mA amplitude, is injected onto the shield of the cable. The cable shield was grounded to an aluminum sheet placed 2 inches below the cable, such that the current path was from the cable shield to the aluminum sheet, back to the generator ground. The open circuit voltage (VOC) was then measured at the end of the cable opposite the injection point. For this configuration, the only way for any current and voltage to couple to the twisted pair inside the shield is through the shield transfer impedance. The schematic of the measurement is shown below. A full demo video of the test, test setup, and the simulation can be viewed below.
And here is the training for how to create the model:
The simulation training and data files can be downloaded here. The data files from the measurement are named “measCurrent.dat” and “measVoltage.dat”. Once the simulation is completed, the results can be compared with the measurement. Please contact EMA if you have any questions about the test setup, test results, or the training manual.