Angier -

The Lightspeed ignition has two RPM outputs - a 0-10v pulse at 3x crankshaft
speed which can drive most tachometers, and a 0-30mV output that drives the
Simpson DPM (digital panel meter). 30mV equates to 3000rpm. Some quick math
indicates that your Simpson is seeing 0.11 to 0.13 mV from the Plasma III. A
small voltage like that is susceptible to ground noise which would explain
your reading. About the only precaution you can take is to make sure the
shield goes from the Plasma III to the low input of the Simpson and nowhere
else. But if you're using the pre-wired harness Klaus probably took care of
that for you.

The same is true for the manifold pressure - 30mv equates to 30" mercury. So
a discrepancy of 0.2" is quite a small voltage difference. The only way to
know for sure which instrument is correct would be to use a calibrated
pitot-static tester from an avionics shop. A simpler (and cheaper solution)
would be to adjust your MVP-50 so it matches the Simpson!

A word of caution - if you call Klaus with questions he'll want to know
whether you have Plasma III version A, B, or C. -Adam Molny
L2K #151 first high-speed taxi completed!

-----Original Message-----
From: Greenbacks, UnLtd. [mailto:N4ZQ@VERIZON.NET] Sent: Thursday, March 08, 2012 7:49 AM
To: lml@lancaironline.net
Subject: Re: Lightspeed Ignition

I have dual Plasma III on N4ZQ.
With engine off(actually, it hasn't been on yet...:-)  ..), the Simpson LCD
display shows RPM fluctuating between 11 and 13RPM.
Is this normal/typical? Also, MP reads .20 lower than MVP-50 MP reading. Nothing over which to lose
sleep, but...splitting hairs is such good fun.

Angier Ames
N4ZQ