MGL Avionics Stratomaster Ultra Horizon XL Owner’s manual
Page 44
The rev counter
The Stratomaster Ultra includes a very flexible rev counter that can be adapted to a very wide
variety of engines. In the main this is done in the Device setup menu under “Basic operation
setup menu” and “Calibration Menu”. Here you enter the number of pulses the rev counter
pickup (whatever it may be) will generate for every ten revolutions. The instrument will
actually use this information to work out revs from the time it takes to complete ten
revolutions of the engine. This way high resolution of the rev counter is guaranteed even if
only one pulse is generated for a single revolution as would be the case for the 912 engine.
The rev counter is available in three variants, one of which is intended for rotor craft such as
small helicopters and gyro planes.
The rotor craft option shows an opposing needle display for engine power (engine RPM) and
rotor speed (or rotor RPM).
Standard RPM rev counter. The scale (maximum RPM) can be selected in the
Basic operation setup menu.
This smaller version of the rev counter can be selected if you have a busy panel
and want to save some space. You select the maximum RPM to display on the
bargraph in the Basic operation setup menu.
The Rotor craft opposing needle RPM and rotor speed display.
Indications can be in RPM or as a percentage relative to a given RPM
setting.
You setup most of these items in the “Rotor craft setup menu”.
About rev counter pickups
Pickups vary from those provided by the engine manufacturers in the form of magneto coil
tapings (Rotax / Ducati) to taping into the primary of a aircraft style magneto.
In fact, anything that is able to provide at least a 5 volt, reasonably stable signal at the rev
counter input of the RDAC EMS system. Signals with a voltage as high as 100 volts can be
used.
On unusual engines it is often a matter of experimenting with various pickup methods to find
a satisfactory solution. Once a stable reading can be obtained, set the calibration of the rev
counter so that correct revs are indicated.
The range of the rev counter is up to 9 999 revs. You should select the scale of the analog
rev counter to just above the maximum RPM. For example for a VW engine you might select
4000 RPM.
Pickups for the Rotor speed sensor range from hall effect sensors, gear tooth sensors to
simple magnetic switches that are closed by a small magnet once per revolution of the Rotor.
You setup the number of pulses generated by 10 revolutions of the rotor in the Rotor craft
setup menu.
