PHD User Guide
12
3.3.1.1.
Analog input connections
Analog inputs are susceptible to system noise, which can affect the accuracy of the signal. Signal
accuracy can also be affected by ground level shift, which can cause inputs to activate when they
shouldn’t.
System noise
To prevent noise pickup on the sensors,
•
Use the shortest possible wires when connecting analog inputs to sensors.
The following diagram shows connect an analog input to reduce system noise:
Internal to product
+5 Vdc Sensor Supply
Sensor Ground
Sensor
Analog Input
Figure 3.3. Analog input system noise reduction
Ground level shift
To reduce ground level shift:
1. Dedicate one of the system ground inputs (GND) to sensors that have dedicated ground wires and
connect all sensor grounds to this system ground input.
2. Splice the other system ground inputs together in the vehicle harness (close to the connector) to
provide a better ground for the noisier low-side outputs and digital circuits.
3. Position the sensor’s ground connection near the system ground connections to ensure that the
signal remains within the digital activation range of the input.
Note:
The system ground inputs are rated for low-current signals, which ensures the sensor’s
ground is very close in voltage potential to the system ground.
Note:
Sensors that don’t have a dedicated ground wire are typically grounded to the vehicle
chassis through the sensor’s body.
