Harmonics

[doylej]

I have some understanding what the harmonics are and such but cant seem to put together where that info would be useful in common automotive diagnosis. Any help or direction to better understanding would be great

[Grant_Baker]

NVH: Noise Vibration Harshness. A harmonic is a noise associated with a vibration, and this vibration has a frequency. Frequency is in the time domain so it can be plotted by the scope. The frequency can be correlated with the speed of components: tires, CV axle, propeller shaft, engine, etc. The road speed, engine rpm, gear ratios, tire size, etc are inputs to the PicoDiagnostics NVH software. Sometimes the input is automatically populated such as by connecting to the OBDII connector. Sometimes the inputs are entered manually by the technician based on service information or an inspection. The NVH kit accelerometers and microphones convert the vibration or sound to a voltage which is categorized and plotted graphically by the NVH software. The software knows the speed at which components are rotating, therefore it can narrow down which component(s) are the suspected cause of the concern by labeling it as "T1" Tire once per revolution, "P1" Powertrain once per revolution, "E2" Engine twice per revolution. With more than one microphone you can see which microphone is closer to the sound of concern and therefore narrow down its source.

[Steve Smith]

Hello and thank you for the posts

They say that timing is everything and this question came up here too viewtopic.php?p=105115#p105115

Could you scroll down to Question 5 where I hope we have answered the harmonics question with several examples

Here is another link that may help
viewtopic.php?p=88781#p88781

Take care…….Steve