AEM 30-6905 Universal Programmable EMS-4 - Manual (Page 275)

Page 275 of 279 EMS-4 Install and Tuning Guide_Rev 1.6
psia
Abbreviation for pounds per square inch absolute. A unit of pressure measurement relative to a
perfect vacuum.
RS232
A common standard used in serial communication between a PC and an engine controller.
RXD
Abbreviation for Receive Data.
Saturated Driver
A power transistor driver that turns fully on for the entire duration of the injector PW. This type of
driver is used with injectors having high resistance coils (typically 12 to 16 ohm) or with injectors
having low resistance coils in combination with a ballast resistor
Sensor Calibration
Sensors used on EFI systems output a voltage that is proportional to whatever the sensor is
monitoring, manifold pressure, coolant temperature, etc. A calibration curve is a 2 dimensional
lookup table that assigns sensor voltage settings to values in particular engineering units.
Manifold pressure will be calibrated in units of pressure, coolant temperature will be calibrated in
units of temperature, either Fahrenheit or Celsius, etc.
Sensor Ground
Also known as analog ground or low reference. The voltage output from a sensor is always
relative to some reference. Most analog sensors use a clean 5 volt high reference and a clean
low reference or sensor ground. Sensor grounds are actually outputs from the ECU. The engine
controller isolates and filters these reference grounds so they are not affected by stray electrical
noise.
Serial
In communication hardware, serial refers to sending data sequentially, one bit at a time over a
communication channel or cable.
Series Circuit
Two or more circuit elements are said to be in series if the same current flows through each of
the elements.
Spark Timing
Time measured in degrees of crankshaft rotation between the spark plug firing event and top
dead center for that cylinder.
Stoichiometric
The air/fuel ratio for complete combustion; all the fuel is burned using exactly all the oxygen in