Page 424 - Understanding Automotive Electronics

2735 | Glossary Page 411 Tuesday, March 10, 1998 1:33 PM

GLOSSARY G

Engine Crankshaft Position: The angular position of the crankshaft relative
to a reference point.
Engine Mapping: A procedure of experimentally determining the perfor-
mance of an engine at selected operating points and recording the results.
Equivalence Ratio: Actual air/fuel ratio divided by the air/fuel ratio at
stoichiometry.
Evaporative Emissions: Evaporated fuel from the carburetor or fuel system
which mixes with the surrounding air.
Foot-Pound: A unit of torque corresponding to a force of one pound acting
on a one foot level arm.
Frequency Response: A graph of a system’s response to different frequency
input signals.
Gain: The ratio of a system’s output magnitude to its input magnitude.
HC: Hydrocarbon chemicals, such as gasoline, formed by the union of carbon
and hydrogen.
Ignition Timing: The time of occurrence of ignition measured in degrees of
crankshaft rotation relative to TDC.
Inductor: A magnetic device which stores energy in a magnetic field produced
by current flowing in it.
Instrumentation: Apparatus (often electronic) which is used for measurement
or control, and for display of measurements or conditions.
Integral Amplifier: A control system component whose voltage output
changes at a rate proportional to its input voltage.
Integrated Circuit: A semiconductor device which contains many circuit
functions on a single chip.
Interrupts: An efficient method of quickly requesting a computer’s attention
to a particular external event.
Lead Term: A control system component which anticipates future inputs
based on the current signal trend.
Limit Cycle: A mode of control system operation in which the controlled
variable cycles between extreme limits with the average near the desired
value.
Linear Region: A transistor operating mode where the collector current is pro-
portional to the base current.
Logic Circuits: Digital electronic circuits which perform logical operations
such as NOT, AND, OR, and combinations of these.
Lookup Table: A table in the computer memory which is used to convert an
important value into a related value from the table.
MAP: Manifold absolute pressure; the absolute pressure in the intake manifold
of an engine.
Mathematical Model: A mathematical equation which can be used to numer-
ically compute a system’s response to a particular input.

UNDERSTANDING AUTOMOTIVE ELECTRONICS 411