Innovate Motorsports LMA-3 - Manual (Page 18)

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value internally until it is started the next time. In vaccuum/boost measurement mode the LMA-3
will then subtract the measured value from the MAP value internally.
For this to work, the LMA-3 MUST be powered by a switched 12V source that switches on before
the engine is started, like the ignition power. This 12V source MUST stay active during cranking.
To give the LMA-3 a chance to measure atmospheric pressure, you must change the way you
start the engine. First, switch ignition on (powering the LMA-3), wait for 0.5 seconds, THEN crank
the engine (starter).
Function 3 of input 4 of the LMA-3 measures vaccuum with a range of 0..30 inHg (gauge) This is
the range intended for normally aspirated engines where the maximum intake pressure can be
atmospheric pressure.
Function 4 of input 4 of the LMA-3 measures vaccuum and boost pressure with a range -14.7 to
29.4 PSIg This is the range intended for boosted engines where the maximum intake pressure
can be up to 29.4 PSI above atmospheric pressure. Vaccuum is typically measured here as
negative PSI. But you can set up any metric you want with LogWorks 2.
8 Measuring Frequencies, custom RPM, or speed
The LMA-3 has the capability to measure frequencies on channels 3, 4, and 5. It converts a
frequency signal (pulses per second) into a voltage (0..5V) to be logged in the LM-1 or a number
between 0 and 1023 to be logged directly by LogWorks. This is useful for measuring custom
RPM ranges, signals from speed sensors or the frequency of MAF sensors with frequency output
(as opposed to voltage output MAF sensors).
The range of frequencies that the LMA-3 can measure can be programmed by with LM
Programmer. The LMA-3 can be set to any frequency range between 0 and 30 Hz for the full
0..5V range to 0..15 kHz for the full 0..5V output (logging) range.
Also, LM Programmer has convenient conversions built in, so you don’t have to calculate the
resulting frequency ranges for speed sensing or RPM sensing yourself. See chapter 10.x for
details.
A frequency input signal must have an amplitude (voltage range of pulse) between 0.5V at the
low pulse point to minimum of 3V and maximum of 40 V at the high pulse range.
NOTE:
The custom RPM feature will work only for even fire tach signals, not for tach signals that
vary their time between pulses during an engine cycle. Use the input 1 RPM functions
instead.
9 Measuring duty cycle
To measure the duty cycle of a signal in channels 3, 4, and 5, the input signal must cover the
same voltage range as for a frequency signal. Duty cycle is defined as the ratio between the time
a signal is active and the total time of the active and inactive time. A signal can be either active
high ( the event, like injector open, happens when there is a high voltage) or active low (the event
happes when the measured signal is at ground or close to it).
Very often the injector duty cycle is to be measured by the LMA-3. A typical fuel injector is
connected to 12V on one side, while the other side is connected to ground when the ECU opens