Floats stick. Probes do not.
Capacitive level sensors measure liquid level continuously without floats, arms or other moving parts. Gill’s level sensors are designed for integration into vehicles, machinery and specialist platforms, with options for different tank configurations, electrical interfaces and operating requirements. Where standard products do not meet the application, custom sensor development may be possible.
How do you measure fuel, oil and coolant level in a vehicle or machine?
A capacitive level sensor measures fuel, oil or coolant level by detecting the change in capacitance along a probe as the liquid rises and falls. There is no float or pivot to wear, stick or jam, which suits tanks exposed to vibration, movement, temperature change and contamination. The output can feed the machine’s own electronics directly.
Fuel, oil and coolant levels need to be measured in environments where vibration, movement, temperature changes and contamination can affect the reading. Tank shapes are often dictated by the available space in the machine rather than by the needs of the sensor.
Conventional float senders use a moving mechanism that can wear, stick or become obstructed. Capacitive sensing measures the change in capacitance along a probe as the liquid level changes, removing the need for a float or pivot.
A continuous level signal can also feed into the machine’s own electronics or monitoring system, supporting level display and, where the wider system is configured to do so, monitoring over time.
Requirements for level sensing
The appropriate sensor depends on the liquid, tank geometry, required measurement, installation conditions and interface to the host system.
Vibration and liquid movement
Vehicles and machines expose sensors to vibration, acceleration and liquid movement. Float mechanisms can wear or stick over time. A capacitive sensor has no moving mechanism inside the tank, although the installation and measurement performance must still be suitable for the application.
No moving parts | Solid-state
Tank geometry and calibration
Tanks are often irregularly shaped or constrained by the surrounding equipment. Gill level sensors can be specified for the installation, including appropriate probe lengths and factory calibration. Changing the tank or installation may require the sensor specification and calibration to be reviewed.
Liquid properties
Capacitive sensing depends on the properties of the liquid being measured. Fuel, oil and coolant applications should be assessed against the sensor’s intended use. For difficult conductive liquids, Gill’s LevelSlick is designed for applications that require a suitable specialist approach.
Electrical interface
The level reading must be compatible with the vehicle or machine’s electronics. Depending on the sensor model, Gill options include voltage, current, RS232 and CAN outputs. The required output should be established before the sensor is selected.
0 to 10 V | 4 to 20 mA | RS232 | CAN
Weight and installation constraints
Weight and available space can be critical on platforms such as UAVs and competition vehicles. Sensor construction, length, mounting and sealing requirements should be considered together when choosing a solution.
Comparing level measurement methods
Different technologies suit different applications. A simple switch may be sufficient for a high- or low-level alarm, while continuous monitoring requires a suitable continuous-output sensor.
| Consideration | Float or reed switch | Resistive float sender | Ultrasonic sensor |  Gill capacitive level sensor |
|---|---|---|---|---|
| Measurement | Switched level points | Continuous resistance-based level | Continuous, non-contact measurement | Continuous level measurement along a probe |
| Moving parts | Depends on design | Float and arm | No moving parts | No moving parts |
| Potential limitations | Moving components may stick or wear | Pivot wear and float-related issues | Performance depends on surface, foam, vapour and installation conditions | Performance depends on liquid properties, probe specification and calibration |
| Output | Switched points | Resistance | Depends on sensor | Voltage, current, RS232 or CAN, depending on model |
| Typical application | Simple high- or low-level alarms | Conventional continuous level gauging | Suitable open or non-contact installations | Continuous level sensing in vehicles and machinery |
A float switch can remain a sensible choice for a straightforward alarm. Capacitive sensing is worth considering when continuous level measurement, the removal of moving parts or integration with the machine’s electronics is important.
Specification considerations
Probe length and tank calibration
The probe must suit the tank’s dimensions and installation. Gill level sensors can be specified and calibrated for the intended application. If the tank geometry changes, the sensor’s suitability and calibration may need to be reassessed.
Liquid compatibility
Do not assume that a sensor suitable for one liquid will perform identically with another. The liquid’s properties and the sensor’s intended application must be considered during selection. LevelSlick is designed for difficult conductive liquids; suitability should be confirmed for the specific fluid.
Output and host-system compatibility
Output options vary by model. LevelLite and LevelPro offer voltage and current outputs, with RS232 for configuration. CAN is available on bespoke sensors. The receiving electronics, wiring and any load requirements should be checked against the chosen model’s documentation.
Bespoke requirements
Some applications require a sensor designed around a specific tank, platform or operating environment. LevelDefend is built to customer requirements for defence vehicles and marine craft. The specification is agreed for each programme rather than assumed from a standard catalogue configuration.
Gill capacitive level sensors
Gill offers level sensors for general-purpose machinery, weight-sensitive platforms, defence applications and specialist motorsport installations. The models differ in construction, outputs and intended application.
LevelLite
Lightweight capacitive level sensor
LevelLite uses a lightweight aluminium construction and sealed electronics for applications where weight and installation conditions matter, including UAVs.
Confirm the exact output configuration for the required model.
LevelPro
General-purpose capacitive level sensor
LevelPro uses corrosion-resistant stainless steel construction and sealed electronics for fuel, oil and fluid-level applications on vehicles and machinery.
Check the current datasheet for the precise configuration and installation requirements.
LevelDefend
Level sensing for defence and marine platforms
LevelDefend is developed to customer requirements for defence vehicles and military marine craft. Its design can address demanding shock, vibration and electromagnetic compatibility requirements, with the specification agreed for the individual programme.
The final design and performance requirements need to be agreed for each application.
Motorsport catch-tank level sensor
Dedicated oil catch-tank measurement
Gill’s catch-tank level sensor is designed for oil catch-tank applications in endurance motorsport. It is ACO Le Mans approved and has an analogue voltage output that rises with oil level.
Confirm the relevant approval and configuration for the intended competition and installation.
insight
Continuous level data and condition monitoring
A continuous level signal can provide more information than a single high- or low-level alarm. When the reading is captured over time by the wider monitoring system, changes may help identify unusual consumption or a falling fluid level that warrants investigation.
For example, a gradual coolant-level reduction may prompt an inspection, while an unexpected change in fuel level may need to be compared with the machine’s operating pattern. These trends are indicators to investigate, not proof of a particular fault.
Level measurement and fluid-condition monitoring are different functions. Gill’s WearDetect monitors ferrous wear debris in oil, providing information about metallic wear particles rather than how much oil remains in the tank. It can complement level measurement, oil analysis and vibration monitoring, but does not replace them.
The full explanation is in Capacitive vs float level sensors
Related applications and resources
IndustryMotorsport and high performance
Fuel, oil and fluid-level measurement for applications where weight, packaging and reliability matter.
ApplicationConstruction vehicle engine monitoring
Level measurement for machinery operating in demanding environments, including dust, mud and vibration.
ApplicationSpecialist level sensing in cement and mining
Level sensing for applications where the liquid and operating environment place additional demands on the sensor.
IndustryDefence and security
Fuel and fluid-level sensing for military vehicles and marine craft.
Speak to our team
Tell us what you need to measure, where and under what conditions. We’ll help you work out the appropriate approach.
Frequently asked questions: fuel, oil and coolant level sensing
A capacitive level sensor measures changes in capacitance associated with the liquid level along a sensing probe. Gill’s capacitive level sensors use a sealed, solid-state design without a float or moving mechanism. The suitability of the sensor depends on the liquid properties, tank configuration and required output.
Float level sensors contain moving components that can wear, stick or become obstructed. Vibration and repeated movement can affect the mechanism over time, while contamination can interfere with its operation. A capacitive sensor removes the float and pivot, although its performance still depends on correct specification, installation and calibration.
Gill offers level-sensing products for fuel, oil and other fluid applications, but a single sensor should not automatically be assumed suitable for every liquid. Capacitive measurement depends on liquid properties, and compatibility must be confirmed for the specific fluid, tank and operating conditions.
Output options depend on the model. LevelLite provides voltage and current outputs, and LevelPro provides 0 to 10 V or 4 to 20 mA. Both use RS232 for configuration, and CAN is available on bespoke sensors. LevelDefend outputs are specified to customer requirements. Check the current datasheet to confirm the options for the exact sensor configuration.
Capacitive level sensors can be suitable for vehicle and machinery applications where vibration makes moving mechanisms less desirable. Gill’s designs have no moving parts inside the sensing mechanism. The sensor must still be selected and installed to meet the platform’s mechanical, environmental and measurement requirements.
Gill can assess custom level-sensor requirements where a standard product does not meet the application. The specification may need to address probe length, tank geometry, liquid properties, electrical interface and environmental conditions. Feasibility, development scope and validation requirements depend on the individual application.
Start with the liquid being measured, the tank’s dimensions and shape, the required measurement range, the operating environment and the interface to the host system. Also consider available space, mounting, supply voltage and any relevant sealing or vibration requirements. These details help determine whether LevelLite, LevelPro, LevelDefend, a specialist product or custom development is appropriate.
Level sensing measures how much liquid is in a tank. Oil-condition monitoring assesses other characteristics of the oil. Gill WearDetect monitors ferrous wear debris, which can provide information about metallic wear within machinery. These measurements serve different purposes and may be used together as part of a wider monitoring system.
Gill level sensors are factory calibrated for the installation. Because tank geometry affects the relationship between liquid height and volume, a change to the tank or installation may require the sensor specification or calibration to be reviewed. Confirm the requirements for the chosen model with Gill.