Click Here for an evaluation report - Vic Leggott

Principle of operation
This system does not use any kind of sender unit in the fuel tank itself. Instead, a small flow sensor is employed. As fuel flows through this device a turbine rotates and generates electrical pulses. Use is made of the fact that the sensor will generate a known number of pulses when a certain volume of fuel passes through it.

The total number of pulses produced by the unit can be counted, and then converted back to a volume in litres, US gallons or Imperial gallons. Hence if the initial amount of fuel in the tank is known, it is a simple matter for the flow meter to monitor the pulses and thus compute the amount of fuel remaining. There is a simple facility to calibrate the sensor to make it extremely accurate.

Knowing the amount of fuel remaining in the tank (and also the rate at which it is flowing out) allows the flow meter to compute the "time to empty". This is the maximum time, based on the amount of fuel which the flow meter thinks is in the tank and the present flow rate, until you run out of fuel.

The fuel quantity in the tank is set on the ground simply using two push buttons, which can be mounted remotely from the display. No more button pressing is required until the next fill up.

An optional ultrabright led (supplied) will illuminate when fuel remaining falls below 1 hour endurance.

A bonus is that the unit will record the total amount of fuel which has passed through the sensor (up to a limit of about 42,000 litres), the time for which the unit has been on since the last switch-on, and also the total "on" time - effectively a Hobbs meter.

A further advantage of this system is the ability to make use of information from a GPS. Most GPS units can be configured to output a data signal, and this signal contains several pieces of information. For example the current date, position, magnetic variation and course over the ground are transmitted. Also available is the ground speed. The Flow Meter uses this ground speed information and can easily convert a 'time to empty' into 'distance to empty'. Additionally the fuel consumption in nautical miles per litre or gallon can be shown, thus allowing the pilot to select the most economical cruising speed. The option to connect a GPS to the unit is a benefit which has previously only been available on systems costing £500 or more.

The display is supplied separately from the control box although connected to it by a grey ribbon cable. The reason for this is that it will then take up the absolute minimum amount of panel space. The use of a backlit liquid crystal display allows easy viewing in both bright and overcast conditions.

Please note that the LCD display is unenclosed (as per the photos) as most builders will wish to build the display into the instrument panel.