Innovate Motorsports LMA-3 - Manual (Page 5)

- 5 -
Input 5 Functions
Function
Indicator 1 2 3 F d =
Functionality Acceleration
(+- 2g)
Acceleration
(+- 1g) Acceleration
(+- 0.25g) Frequency
(straight
frequency,
Speed
sensor,
Custom
RPM
range Duty Cycle External
0..5V
sensors
The LMA-3 also can act as a power supply for user supplied external sensors. The 5V output of
the LMA-3 can supply up to 300mA of current. For this functionality the LMA-1 must be
connected to a switched 12V source in the car. It converts the 12V to 5V to power the sensors.
When no external sensors need to be supplied with 5V power, the 12V connection can be left
open.
1.1 Differential Inputs
The LMA-3’s external connections are differential. This means that each input channel has 2
input terminals. A + terminal and a – terminal. This is to eliminate ground offsets in the signal.
Many times the ground point of a sensor is at a different ground than the LMA-3. Because each
electronic device can only measure a voltage referenced to it’s own ground, differences in
grounding can introduce measurement errors. The LMA-3 measures the sensor signal’s ground
with the – input and them measures the difference between the + and the – input. This way it
“recreates” the sensor signal’s own ground reference as if this input were referenced directly to
that sensor’s ground.
The – input is NOT a ground itself. It is a ground reference input.