Why a Pneumatic Tank Gauge?
Most boats suffer badly from unreliable tank level gauges, this is a particular problem with dirty water tanks. The main problem is the corrosive nature of the salt water in the tank and the fact that float meters are damaged in the tanks.
The measuring device must not be affected by the movement or the corrosive nature of the fluid it is measuring. The best way to achieve this is the way ships and other quality tank meters work. And this is to use pneumatics. This has always proved too expensive to miniaturize for leisure craft use until now.
How does it work?
The new Sterling gauge works on a very simple principle. If you put a small tube to the bottom of any liquid, then pump air through the tube to remove all the fluid from it, then the atmospheric pressure or back pressure on the liquid is directly proportional to the depth of the fluid (taking density into account). For this to work, we need a simple pipe (approx 2 – 3 mm diameter) from the top to the bottom of the tank, then pump air through the pipe and measure the back pressure of the air (the transducer) and display it on a display panel.
Well not that simple, we need a compressed air pump with a complex software program control to reduce power consumption to milliamps and to return a highly accurate reading, all at a sensible cost.
The Sterling Tank Gauge is a fully programmable system, where you program in the following information, 1) tank depth 2) fluid density (water, diesel, dirty water, petrol) 3) operation mode (i.e. a water or fuel tank would require the alarms etc to go off when the tank is empty, but a dirty water tank would require its alarms when it is full). With these three pieces of information simply connect the unit to a pipe which is about 10 mm of the bottom of the tank and the L.E.D. display will give a good indication of the depth. For a more accurate analysis the L.E.D display can be connected to the optional L.C.D display which will scan up to 8 tanks and display the depth in % full in rotation, when the fill button is pushed on the tank, for example tank 6, then the L.C.D. display will lock on to that channel.
The system must only be used where the pump sensor unit can be fitted above the level of the highest point on the tank system, i.e. above the height of the deck filler system or a U bend in the tube going above the filler. i.e. in a overfill condition liquid must not run into the unit.