The 5 Critical Dimensions

INTRODUCTION

There are only 5 critical features, or types of information, from five primary signal types signals that we should consider important, because the vehicle's PCM considers them important. these are the 5 critical dimensions of the signal.

The five critical dimensions of automotive electronic signals are the equivalent of the "electronic words" that make up a sentence of intelligent electronic communication between sensors, control units and other devices in the system. The Five Critical Dimensions are what the vehicle's PCM "reads" and "writes" with. It "reads" what a sensor is telling it by decoding its "Critical Features" and "writes" with them to give instructions to devices within the system that perform certain tasks, like injector on-time, etc.


THE FIVE CRITICAL DIMENSIONS ARE:

1. Amplitude

2. Frequency

3. Shape

4. Pulse Width

5. Pattern


CRITICAL DIMENSION DEFINITIONS:

Amplitude - The voltage of the electronic signal at a certain point in time.

Frequency - The time between events, or cycles, of the electronic signal, usually given in cycles per second (Hertz).

Shape - The signature of the electronic signal; its unique curves or comers, etc.

Pulse Width - The on-time, or duty cycle of the electronic signal.

Pattern - The repeated patterns that have specific messages, like sync pulses that tell the PCM that cylinder #1 is at top dead center, or a repeated pattern in the serial data stream that tells the scan tool the coolant temperature is 2100.

Each of the five signals types use one or more of the Five Critical Dimensions, alone or in combination, to make up "intelligent electronic sentences." Diagnosis Using A Labscope