SERVICE MANUAL NUMBER 24
FUEL INJECTION DESCRIPTIONS AND SYSTEM OPERATION
TWO-WIRE SENSOR (ECT)
The following figure is the schematic of a 2-wire type sensor. This sensor is basically a vari-
able resistor in series with a fixed-known resistor within the computer. By knowing the values
of the input voltage and the voltage drop across the known resistor, the value of the variable
resistor can be determined. The variable resistors that are commonly used are called therm-
istors. A thermistor’s resistance varies inversely with temperature.
b
a
c
d
e
2-Wire
Sensor
a - Typical Sensor
b - ECM
c - Signal Sensor
d - 5 Volt
e - Sensor Ground
Digital Signals
Digital signals are also variable, but not continuously. They can only be represented by dis-
tinct voltages within a range. For example, 1 V, 2 V or 3 V would be allowed, but 1.27 V or
2.65
V would not. Digital signals are especially useful when the information can only refer
to two conditions - YES and NO, ON and OFF, or HIGH and LOW. This would be called a
digital binary signal. A digital binary signal is limited to two voltage levels. One level is a posi-
tive voltage, the other is no voltage (zero volts). As you can see in the following figure, a
digital binary signal is a square wave.
d
e
g
a
c
f
h
b
Digital Binary Signal
a - Voltage
b - Time
c - Lo
d - Hi
e - On
f - Off
g - Yes
h - No
Index
90-861327
OCTOBER 1999
Page 5D-13
| Categories | Mercury MerCruiser Manuals |
|---|---|
| Tags | Mercury MerCruiser 305 CID, Mercury MerCruiser 350 CID |
| Model Year | 1998, 1999, 2000, 2001 |
| Download File |
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| Document File Type | |
| Copyright | Attribution Non-commercial |
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