Fuel Level Senders – The Inside Story

It goes without saying that every piece of equipment which is powered by an internal combustion engine needs a means of fuelling so that it runs for as long and efficiently as possible. ICEs are used in cars, motorcycles, race vehicles, ATVs, utility vehicles, compressors, generator sets etc. to name but a few, and the problems which has always pertained are how to contain the fuel, know how much is left and how best it should be stored for the user’s benefit, safety and security.

Fuel containers are typically steel or plastic because these materials have traditionally been used and are relatively inexpensive, but many modern race fuels contain some very aggressive additives so these tanks need to be made from carbon fibre or be reinforced with Kevlar. Truck and lorry fuel tanks are often rectangular in shape which allows easy fitting of a simple swing arm type fuel level sender because there are few baffles or reinforcing struts to impede the sender’s float arm. This sender outputs an ohmic value usually to a gauge but suffers from inherent failures resulting from fuel slosh which causes the resistance track to be constantly wiped by the float arm and therefore reduce the sender’s service life.

Modern vehicle designs require the designer has to be increasingly inventive is adapting the profile of the tank to not impact upon the increasingly complicated aesthetics of the vehicle. The swing arm sender is unsuitable for this kind of tank which therefore allows the use of solid state electronics sensors and senders which can be programmed to the tank profile and give accurate readings of the fuel level. Additionally, sophisticated electronics engine management systems now require voltage or PWM (Pulse Width Modulated) inputs not available from the swing arm sender. Accordingly, the capacitance level sender is an ideal product for answering all of today’s technical demands because there are no moving parts to wear out; capacitance technology is reliable and well proven; the sender’s outputs match all analogue and digital ECU inputs; it can be programmed to compensate for irregular tanks shapes and to smooth out blips caused by fuel slosh and has many other features.

The past few years have seen the cost of fuel escalate to a point whereby its theft is now a major factor in the methods used to secure the tank. One often used means is to have the fuel filler neck positioned behind a lockable panel and a second way is to fit an anti siphoning device. Furthermore, the designer can specify fitting a capacitance fuel level sender which can output the level to a remote monitoring telemetry system so regular readings of fuel level can be recorded and should a sudden drop in level be observed, this could indicate fuel theft and the cause of the loss be investigated quickly. Additionally, in a vehicle application the fuel consumption may be measured accurately and provide information which shows if it is being driven in an economical and appropriate manner.

Although the fuel supply process is considered a poor relation compared to emissions legislation, for example, this article demonstrates that customers of industrial equipment giving more consideration to this aspect of product design, which will result in further developments of fuel level senders with increasing numbers of new and challenging applications.