MGL Avionics Stratomaster Ultra “L” Owner’s manual
Page 74
(Fuel flow sender – continued from previous page)
Using other Flow Senders
It is quite possible to use Flow Senders other than the RS device. In this case ensure that the
Sender outputs a 5V TTL square wave or a similar signal. The Stratomaster interface electronics
will adapt to a variety of different voltages and pulse shapes as it contains a schmidt-trigger input
stage. The calibration factor can be entered in a wide range making the unit particulary suited to
other Flow senders.
The supply output terminal for the Sender provides a positive, regulated 5 volt output. This may
be used to power the Flow Sender provided the Sender will not draw more than 40 mA of current.
Should your sender require a higher voltage or more current, then you must supply the sender
from a different power source. Exceeding the rating on the Stratomaster Flow sender supply
terminal can affect the operation on the unit negatively or even damage it.
Settings for the calibration factor for other Flow senders can be estimated, using the following
formulae:
Estimated calibration factor:
1000 / (Number of pulses per 4 second period for 1 liter/hour flow)
Recommended Calibration Factors for RS Flow Sender Part No. 256-225
With jet installed = 130. Recommended with flow rates below 60 liters/hour maximum.
Without jet installed = 750. Recommended with flow rates above 60 liters/hour.
Please refer to the leaflet included with the Flow Sender for information on pressure drop vs. flow
rate, wetted materials etc.
It is your responsibility to ensure that the flow sender used is compatible with the fuels
you intend using. We have found the RS sender to be very compatible with automotive
fuels used in South Africa, many of which contain methanol. 100LL AVGAS also appears
not to harm the sender in any way. We have exposed a RS sender continuously to our
automotive fuels for a duration of two years without any noticeable ill effect on the sender.
However, despite this MGL Avionics or its appointed agents cannot assume responsibility
for any incident or damage, even loss of life by whatsoever cause connected with the fuel
flow sender or the Stratomaster Flight Instrument. Usage of this or other senders is your
own sole responsibility.
If you do not agree with the above statement you must not use the fuel flow sender.
Note to Pilots: (Even though this is the installation manual)
You must always have a visual indication of the fuel level available, either by means of a sight
glass, direct tank observation or a known, reliable secondary fuel level gauge. Fuel level
indication by means of calculated fuel burn is subject to errors both by entering incorrect starting
fuel levels as well as mechanical problems causing the flow sender impeller to turn too slowly,
resulting in under reading fuel burn and thus over reading remaining fuel.
As pilot in command of an aircraft it is your responsibility to ensure that you have sufficient fuel to
reach your intended destination. Always ensure that you have a generous amount of reserve fuel
and never use your reserve fuel except in an emergency if it is unavoidable.
