Page 423 - Understanding Automotive Electronics

2735 | Glossary Page 410 Tuesday, March 10, 1998 1:33 PM

G GLOSSARY

Comparator, Analog: An electronic device which compares the voltages
applied to its inputs.
Compression Ratio: The ratio of the cylinder volume at BDC to the volume
at TDC.
Control Variable: The plant inputs and outputs which a control system
manipulates and measures to properly control it.
Conversion Efficiency (Catalytic Converter): The efficiency with which
undesirable exhaust gases are reduced to acceptable levels or are converted to
desirable gases.
CPU: Central processing unit; the calculator portion of a computer.
Cutoff: A transistor operating mode where very little current flows between
the collector and emitter.
D/A (also DAC): Digital-to-analog converter; a device which produces a volt-
age which is proportional to the digit input number.
Damping Coefficient: A parameter which affects a system’s time response by
making it more or less sluggish.
DEMUX: Demultiplexer; a type of electronic switch uses to select one of sev-
eral output lines.
Diesel: A class of internal combustion engine in which combustion is initiated
by the high temperature of the compressed air in the cylinder rather than an
electrical spark.
Digital Circuits: Electronic circuits whose outputs can change only at specific
instances and between a limited number of different voltages.
Diode: A semiconductor device which acts like a current check valve.
Display: Advice which indicates in human readable form the result of mea-
surement of some variable.
Drive Train: The combination of mechanisms connecting the engine to the
driving wheels including transmission, driveshaft, and differential.
Dwell: The time that current flows through the primary circuit of the ignition
coil for each spark generation.
Dynamometer: A device for loading the engine and measuring engine
performance.
EGO: Exhaust gas oxygen; the concentration of oxygen in the exhaust of an
engine. An EGO sensor is used in closed-loop fuel control systems to indicate
rich or lean A/F.
EGR: Exhaust gas recirculation; a procedure in which a portion of exhaust is
introduced into the intake of an engine.
Electronic Carburetor: A fuel metering actuator in which the air/fuel ratio is
controlled by continual variations of the metering rod position in response to
an electronic control signal.
Engine Calibration: The values for air/fuel, spark advance, and EGR at any
operating condition.

410 UNDERSTANDING AUTOMOTIVE ELECTRONICS