Identifying and Dealing with EMI, searching and searching Options

[McMark]

I would like to spend some serious time doing a qualitative analysis of the EMI that is probably going on in my engine bay. I've been searching Google for some write ups that might help me get started, but everything seems to be quick marketing blurbs for every electronics company on the planet. Does anyone have some links or books or anything that might help me?

Here is how I would like to approach the problem:
1. Evaluate my current situation.
2. Identify the sources.
3. Implement effective corrective measures.
4. Judge the effectiveness of my efforts.

This is probably over the top, but being the son of an engineer makes me think this way. (IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif)

So give me your best links and books regarding identifying and dealing with EMI, please.

[TonyAKAVW]

Never underestimate the need for a good source of power. Start off by making sure that your power supply is clean and can deliver sufficient current for the kitcarlson. That means big enough wire, and filter capacitors at the input unless they are present on the kitcarlson circuit board.


After the power supply is guaranteed good and noise free....


An oscilloscope could be a good way to start looking at things. In general you want to use an oscilloscope in parallel. Touch the tip of the probe to the line in question and ground the probe ground to as near a ground as possible. I would guess anything more than 4-5 inches away is probably too much. So that pretty much rules out the battery post as your ground for most things unless you have a very tiny engine.

I would think that rather than starting by finding your sources of noise, find those components which are sensitive to it and figure out how to shield them. EMI from igniton can probably be reduced, but the fact is that you have very high voltage being switched, and thats just bound to cause problems.

lapuwali has excellent suggestions. Shielded twisted pairs is the way to go for sensors, and shield only at one end. bd1308's point about too many ground points can be right. Tiny differentials in voltage from one ground point to another can result in ground loops, and cause noise issues.

I'm not sure how the kitcarlson electronics are designed, but its possible to add components such as capacitors and inductors to filter noise. Depending on the sensor however, the values of these might be critical.

So I would start by looking at what sensors are picking up noise and shield them. Trying to reduce generated EMI is probably not the best awy to go.

I have an interesting article on grounding that I can send you if you are interested.


-Tony