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How Fuel Level Sensors Work

fuel gauge

Remote sites typically run off sustainable and uninterpretable energy sources. Primarily commercial electricity, with some wind turbine and/or solar source to supplement. Some gear, however, requires liquid fuel that requires regular refueling for operation. Now how do you track fuel levels for remote sites, especially for a lot of locations?

When it comes to monitoring how much fuel is in your tanks, many options exist. Some are basic sight-only solutions. Either open the cap and look or maybe you get lucky and have a viewport or a gauge to look at. This requires techs to be in the field constantly to track levels manually.

This not only increases costs through commuting and labor expense but also has room for error. If a mistake results in a fuel delivery delay, you could lose a site and have some unhappy customers.

Fuel level sensors (aka fuel gauges) are devices that allow technicians to monitor fuel consumption so they know when their tanks need to be refilled.

Some solutions may work for home-owner projects. When it comes to industrial applications though, there are more robust solutions. There are basically two kinds of level monitoring: switches and sensors (also known as senders). Both allow for automatic response to level events but the events are significantly different.

Fuel Level Switches

Fuel Level Switches is a float type fuel level sensor that operates on a simple principle. Utilizing a dry-reed switch and a float, it provides a signal path when the liquid is below a specified level. When the liquid is above the specified level, the signal path is broken. The signal is then monitored by a Remote Telemetry Unit (RTU) using a digital input.

This data can be processed locally for on/off status and possibly local alert. The data can also be sent to a Network Operating Center (NOC) for Remote Alarm Monitoring and Control if you have a Supervisory Control and Data Acquisition (SCADA) system in place.

The signal is clearly a digital signal. A digital fuel level sensor does not provide any hint of what the liquid level is or how far above or below the switch point it may be at any point in time. The signal simply switches between Off and On when the float moves and crosses the switch point.

Fuel Level Sensors

Fuel Level Sensors (or sending units) use a different approach. Using a variable resistance component and a similar float, they provide a signal that varies between two stop values. Fuel Level Sensor typically provide a 4-20mAmp or 0-6Vdc output.

The signal can be monitored by an RTU using analog input. This data can be processed locally against thresholds (ideally user-defined) for out-of-range conditions and local alerts. This data can also be sent to a NOC for Remote Alarm Monitoring and Control by a SCADA system.

Notably, this data is analog data and provides basically a real-time indication of the liquid level. Alarm events are generated by the RTU or by the Remote Monitoring and Control system by comparing the monitored level against one or more thresholds.

Summary of Advantages

Both Fuel Level Monitoring solutions allow for better management of your fuel levels. A more controlled response due to continuous monitoring. More efficient management by getting rid of site visits to check level or to fill tanks that are still well above the refill level.

Both improvements can be part of a Control solution for Fuel Level Monitoring. You will save time, reduce costs, and prevent gear downtime. A win/win for you and the customers that depend on your service.