3.3
Resistive Sensors on A Channels
Daqu — Manual
Special caution should be applied when dealing with fuel level sensors. If they
are resistive type, they should be connected to E channel.
3.3
Resistive Sensors on A Channels
Resistive sensors are often used for various temperature probes, pressure sen-
sors, fuel level probes, trim positions, etc. The resistive sensors can be con-
nected either to A or to E channels. The principles are a bit different regarding
to the channel type used. This section describes connection to A channels and
section 3.4 describes connection to E channels.
For A channels, two basic schematics can be used, based on the sensor type.
One wire sensors have slightly simpler schematics, but they are more
sensitive to ground loops. When a large current consumer is turned on,
sensor values may
jump
a bit, sometimes they may even go crazy.
Two wire sensors have slightly more complex schematics, but they are
less susceptible towards large currents.
3.3.1
One Wire Sensors
Some sensors connect with only with one wire. The wire is connected to + pin
of A channel. Although it seems that there is no second wire, in fact it is.
The “invisible” ground wire is provided by the engine block. This means that
negative terminals of selected A channel must be connected to the engine
block, which acts as a second wire.
Figure 4 illustrates such situation for two resistive sensors. A thick ground
wire (use AWG 17 or less) must be routed directly from the engine block
close to Daqu, where it is split and connected to negative terminals of one
wire resistive sensors.
In theory, any system ground point could be used to connect the negative
terminals. In practice this is causing problems (ground loops) and taking
ground directly from the engine block and splitting this ground close to ter-
minals works the best.
There may be several one-wire resistive sensors connected to Daqu. Figure
5 illustrates situation where two CHT, one oil temperature and one resistive
oil pressure sensors are connected. They all are one wire sensors and all are
grounded via engine block. The engine block is connected with one AWG 17
wire, which leads to the splitter and from the splitter separate wires lead to
each negative terminal.
©
Kanardia
2019
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