Dynon Avionics EMS-D120 Installation Guide - Manual (Page 18)

Transducer Installation
Tachometer
Dynon Avionics does not sell a tachometer transducer.
Depending upon existing equipment and engine type,
you have a few options for connecting the tachometer
inputs on the EMS-D120. See the relevant subsections
below for your particular method. You may connect
different types of signals to the two different RPM inputs (e.g., p-lead to RPM Left and a 12V
transducer to RPM Right). Once you have connected the tachometer inputs according to your
engine and transducer type, you must set the appropriate pulses/revolution as described on page
5-8.
TACHOMETER TRANSDUCER
Pin Color Function
32 White/green RPM Left
33 White/blue RPM Right
If you have a standard tachometer transducer (usually with a 12V output), you may simply
connect its output to the RPM Left input on the EMS-D120. Ensure that you follow all
recommendations given in the manual for your individual tachometer transducer.
P-LEAD PICKOFF (LYCOMING AND CONTINENTAL)
If you do not have a standard
tachometer pickoff, you must
follow the instructions below. The
magneto P-lead has high voltages
which can very easily damage the
EMS-D120 if not dealt with
properly.
Use the two included 30kΩ
resistors (color bands: orange,
black, brown, red, brown; connect
in either direction) to attach left
and right P-leads to the RPM Left
and RPM Right inputs on the EMS-D120. Connect them as shown in the following diagram. It is
important to connect each resistor as close as possible to the spot where you tap into the P-lead.
This minimizes the length of cable carrying high voltage spikes. 6 cylinder Lycoming engines
sometimes need more inline resistance to prevent false readings by the EMS-D120.
If, after setting the PULS/REV R and L values as described on page 5-8, you see higher
than expected RPM or unstable values, you may need to increase the series resistance to
as high as 150kΩ.
TRIGGER COIL (ROTAX)
The Rotax 912 engines have a 5 th trigger coil for the purposes of electrically monitoring rev
counts. This trigger coil outputs to a two-wire harness. Connect either of the two wires to
ground; connect the other to one of the included 30kΩ resistors (color bands: orange, black,
brown, red, brown; connect in either direction). Connect the other end of the resistor to the RPM
Left input on the EMS-D120.
3-4 EMS-D120 Installation Guide