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Chapter 14: Inputs- Using
General Input Notes
Important general information
Engines running CDI ignition, copper core plug leads and/or non-resistive spark plugs emit massive
radiated interference. This may cause unstable readings or interfere with DYNertia3’s operation (PC
communication may fault). We suggest you follow the wiring information carefully, particularly in
regards to keeping all wiring as far as possible from the ignition system!
Input channels measure 0-5V or 0-15V depending on position of the “Input voltage select” switch for each channel.
DYNertia3’s processor actually measures 0-5V only, so when you select the 0-15V range you are switching in some
circuitry that divides the input voltage by 3 before it is actually measured.
Note: Whatever switch settings you have used or voltages/sensors you are measuring you will need to check the
settings in the ‘Setup’ menu under ‘Sensor Configuration’ to let DYNertia3 know the voltage range, display units and
calibration details if required. This is covered at the end of this chapter.
The 5V sensor supply is sourced from DYNertia3’s internal regulator so avoid excessive loading. Most sensors you will
power from the 5V supply will draw only very small current, however faulty sensors or shorted wiring must be avoided.
This switch selects for each channel the voltage range and also if a
‘Pullup’ resistor is required, as it is for resistive sensors like standard 2
pin automotive temperature sensors (not thermocouples).
Input Voltage Select- Selects the voltage range 0-5V or 0-15V
Pullup Select- Connects internally a 1KΩ resistor between the input terminal and internal 5V supply. This saves you
from needing to add a resistor externally for sensors that work by changing their resistance.
Wiring inputs for best results
Screw type terminals must be tight or contact will be troublesome. To avoid loose connections, especially when wiring is
frequently changed, we suggest fitting crimp ferrules (called ‘bootlace ferrules’) to the wire ends.
DYNertia3’s 0-5V (or 0-15V), 10 bit resolution allows voltage steps as small as 5mV (15mV with 0-15V settings) to be
measured but in practice its signal noise that limits this measurable voltage.
There are certain precautions that can be taken to maximise the performance and minimize the effects of interference-
Use a separate Power supply battery for ‘RPM Adapter’ if used so it can remain isolated from DYNertia3
It is best to avoid linking into the vehicle/engine if at all possible, run sensors from an isolated supply source
such as the battery powering DYNertia3. Sharing the vehicle ground/power is a major source of measurement
noise and this should always be considered when performing data acquisition during vehicle testing.
Run all wiring well clear of any large current carrying wires (eg electric fans), mains leads and particularly as far
as possible from high voltage sources such as ignition systems and secure well.
Connect all grounds to a common point (star ground) as this will reduce voltage differences between sensors
and the measuring system. The best earth location is at the battery negative terminal (DYNertia3 supply).
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