Pin Injection Level Comparison
To make sure your design is compliant with your DO-160 Pin Injection Level requirement you must first understand what to focus on. Not all waveforms are created equal.
Below is an example of the Level 3 pin injection waveforms
Level 3 Pin Injection Waveform Analysis
At first glance, you might consider looking at WF3 because it is two times higher in voltage. This would be a mistake as I will show you.
If you want to cut right to the chase, always look at WF5a. This is because of two reasons.
1. WF5a is longer in duration. Below are the waveforms stacked up against each other in time and voltage. Notice how short the WF3 voltage is applied.
Additionally, if you have read http://aerospacepal.com/do160g-wf3-lightning-testing/ you would know that with proper design the voltage seen can be 10x less than the spec level.
Pin Injection Level Comparison Voltage
2. WF5a has a source impedance of 1 ohm. This compares to a larger source impedance of 5 ohms for WF4 and 25 ohms for WF3. When protecting against lightning power is king (not voltage). Below is how the waveforms stack up against one another in power.
Just to verify this I checked a great tool by Vishay called the Pulse Energy Calculator
Using the information in the DO-160 waveforms I was able to calculate the energy in WF5a and WF4 in under a minute. The source impedance is simply R = V/I or Resistance(Ω) = Voc/Isc
WF5a = 6.39370215 J
WF4 = 0.84772226 J
Thanks for Reading,