Epsilon - fuel level sensors

Sensor is purposed for fuel level measurement in containers and fuel tanks of vehicles. Sensor can be used with equipment that supports unified communication protocol Epsilon Data Exchange. Sensor has the electronic galvanic isolation through interface and power-supply circuits. Fuel level measurement is provided by a measuring head together with the probe submerged in fuel, which acts as a condenser, which capacity linearly depends on a fuel level in a tank.

EPSILON® ESx-H digital RS-232, RS-485 capacitive fuel level sensor is designed to measure fuel level in vehicle tanks and reservoirs with high precision (99% accuracy).

Main advantages:

High-resolution of the sensor, linearity, temperature stability;
Calibration table inside the sensor head. Allows transferring data directly in liters;
Galvanic isolation. Protects sensor head from power surges;
Monolith construction;
Wide range of possible probe length from 15 to 300 cm;
Ease of installation. Any hack saw can be used to cut the probe.

Sensor description

Sensor is purposed for fuel level measurement in fuel tanks of vehicles and stationary fuel tanks. Sensor can be used to measure level of other nonconductive liquids.
ES2-H, ES4-H sensor can be used with equipment that supports unified communication protocol Epsilon Data Exchange (hereinafter - EDE).
ESA-H model sensors can be used with analogue interface devices.
Sensor has electronic galvanic isolation through interface and power circuits.

Additional features

Model ES2-H sensors provide frequency interface (signal outputting from 500 to 1500 Hz frequency with linear frequency dependence vary with measured level of fuel). Also, model ES2-H sensors can provide analogue interface (signal outputting from 0 to 10 V voltage with linear voltage dependence vary with measured level of fuel), when using FV-10 frequency-to-voltage converter.

Operation principle

A measuring head together with a sensor probe submerged in fuel provides fuel level measurement.
Sensor probe acts as a condenser, which capacity linearly depends on a fuel level in a tank.
Measuring head of the sensor performs linear conversion of sensor probe volume into fuel level digital code, processes acquired digital information with averaged results, measures sensor head temperature and outputs data in unified EDE protocol through RS-232 or RS-485 interfaces (for ES2-H and ES4-H models) or through analogue output (for ESA-H model). Fuel level data outputs in 16-bits (additionally, data output can be selected in 10-, 12-, 14- or 16-bits), temperature data outputs in 8-bits.
To measure the volume of monitored fuel calibration of fuel tank must be performed. This procedure determines volume-level code dependence of fuel.
Calibration procedure and installation of data exchange parameters (by using “EP30_Install” software) described in appendix A of “EH.000 IM. Installation Manual”.
Data exchange protocol EDE can be found in appendix B of aforementioned document.
The process of firmware updating and methods of saving and restoring configuration data described in appendix B of aforementioned document.

A measuring head together with the sensor probe provides fuel level measurement.

Measuring head

Measuring head contains:
- capacitymeter;
- digital circuit for data processing;
- data exchange device;
- power supply regulator and circuit for protection of incoming and outcoming electric circuits.
Sensor is connected to the external devices by the interface cable. Capacity meter performs conversion of current probe volume into digital code. Conversion is a linear function with variable parameters.
Digital circuit for data processing manages the capacity meter performance (limits of measurement, offset nulling, etc.), temperature compensation and received data scaling.
Data exchange device performs data exchange with GPS trackers, save/load of sensor calibration and configuration data and remote updating of embedded software. Sensor is mounted on the tank with self-drilling screws. Gasket ensures tightness between tank and flange.

Fuel probe

Fuel probe is a coaxial capacitor formed by an aluminum alloy tube (outer electrode) and an isolated aluminum rod (inner electrode). Required centering of the rod is achieved by placing a plug on the edge of the fuel probe and by isolated inner position-spacers.

Installation of the sensor

Evaluation of fuel probe length when ordering

To evaluate the proper fuel probe length it is necessary to measure fuel tank depth in place of intended sensor installation and to calculate length of fuel probe according to the formula:
Lm = L- Δ,
where Lm – approximate length of fuel probe as per order;
L– tank depth in place of intended sensor installation;
Δ - distance between measuring part and tank bottom.
Recommended values for distance Δ:
- Δ = 15…20 mm – for rigid metal tanks (the deeper the tank the bigger the distance);
- Δ = 30 mm – for tanks without enough rigidity (such as plastic tanks of considerable height).
During installation process, the necessity of reducing fuel probe length may arise (on-site).
You can find the procedure of reducing fuel probe length in “EH.000-EN IM_ Installation Manual”.

Technical characteristics

Parameter or characteristic name	Unit	Value	Notes
Operational temperature range, °С	°C	– 40 … + 75
Mode of operation		Continuous
Ranges of permissible reduced error of level measurement	%	± 1,0
Code length of presentation of measurement results	bit	10/12/14/16	Level
Code length of presentation of measurement results	bit	8	Temperature
Power supply voltage, operational range	V	+9,5 … +36	Nominal
Current consumption	mA	25
Acceptable exposure of impulse voltage through power circuits		+ 120, long-term + 180 V, 1 sec. - 1000 V, long-term
Acceptable short-term exposure of potentials difference between signal ground and body of measuring head		±1500 V, 1 sec.
Digital interface		RS-485	ES4-H models
Digital interface		RS-232	ES2-H models
Exchange rate through the serial port, bps		2400, 4800, 9600, 19200, 38400, 57600, 115200	programmed
Frequency interface (when using ES.700 compatible device), Hz		500…1500	ES2-H models
Analogue interface. Upper an lower limits are setting by software in the range of, V		0…10 (default)	ESA-H models
Analogue interface (when using FV-10 Frequency-to-voltage converter), mV		0…10
Height of a measuring head over a tank top, including flange and gasket	mm	26