Tech Talk; Q&A; Voltage Spikes And Grounds: The Shocking Truth - DigiCore Technology Ctrack iS100 Series II Installation Manual

9. TECH TALK

9.1. Q&A
Before going through the trouble-shooting procedures for the Ctrack Insure Unit, we should take a
stroll along the Automotive Playground and discuss the "Mysterious Spike", the consequences of a
bad ground, EMI and other important stuff you should know.
What is EMI? Electromagnetic radiation that adversely affects circuit performance is generally
termed EMI or electromagnetic interference. Many types of electronic circuits are susceptible
to EMI and must be shielded to ensure proper performance. Conversely, emissions radiating
from sources inside electronic equipment may threaten circuits within the same or nearby
equipment.
What is EMI shielding? Shielding is the use of conductive materials to reduce radiated EMI by
reflection and/or absorption. Shielding can be applied to different areas of the electronic package
from equipment enclosures to individual circuit boards and cables. Effective placement of
shielding interrupts the path of the electromagnetic waves.
What does Grounding have to do with EMI shielding?
Grounding issues affect both safety and EMI emissions. Conductive components are grounded
to protect equipment users from electric shock. If a system is properly grounded, all conductive
elements, which a user might touch, are theoretically at zero potential. Shielding against EMI
emissions is commonly provided by a conductive enclosure. The separate parts of the enclosure
must be electrically connected and grounded for the shielding to work. Disruptions in the
conductive continuity between parts adversely affect shielding performance. Proper grounding of
PCB's and shielding enclosure components is also a method for reducing board-generated EMI.
However, improper or ineffective grounding may actually increase EMI emission levels, with the
ground itself becoming a major radiating source.
9.1.1.

Voltage Spikes and Grounds: The Shocking Truth

Spikes
Voltage spikes are produced whenever a magnetic field collapses. When current is turned off to
any coil, and inductive voltage is created that is many times higher than the input voltage. This
is the principle on which the ignition coil works to create the thousands of volts necessary to
bridge the spark plug gap.
However, when voltage spikes are created in circuits where we don't want them, they can cause
serious problems. There are two general spike sources: coils and contacts. Consider for a
moment the number of coils in today's cars, besides the ignition coil, there are numerous relays
Revision: 02 05 December 2012
DigiCore Technology (Pty) Ltd
P.O. Box 68270, Highveld Park 0169, South Africa
Ctrack iS100 Series II Installation Manual
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