Capacitance Fuel Contents Gauge and Accessories for Liquid Natural Gas (LNG) Vehicles

A capacitance fuel gage consists of a sender that converts a signal from a variable capacitor in the fuel tank into a signal usable by the vehicles contents gage on the dash. The result is a measure of the mass of fuel in the tank, independent of pressure or temperature. AFS manufactures capacitance senders for LNG, liquid hydrogen, liquid propane as well as other cryogenic fluids.

Skip to [Capacitance Gauge Operation | Capacitance Gauge Sender | Fuel Gauge Test Instrument | Accessories]

Capacitance Gauge Operation

The Liquid Natural Gas (LNG) capacitance fuel gauge consists of three basic components: the variable capacitor inside of the LNG tank, the fuel gauge sender, and the fuel gauge.

The variable capacitor inside of the fuel tank consists of two concentric tubes or two parallel plates that run from the top to the bottom of the tank. As the tank fills with LNG the gap between the plates also fills causing the capacitance of the variable capacitor, measured in picofarads (pf), to change with liquid level. The capacitance signal is carried out of the tank through an electrical feedthrough to the sender.

The fuel gauge sender is an electronic device that converts the input signal from the variable capacitor into an output signal compatible with the fuel gauge. AFS manufactures over 80 LNG fuel gauge senders to interface with a variety of OEM dash boards or fuel gauges. Our senders can output resistance, voltage or current as required by the vehicles electronics. The senders are hermetically sealed for outdoor use and will operate normally from -40 to +160 F. All senders comply with European emissions and immunity requirements and are CE or e-marked for use in the EU.

The fuel gauge is simply the display of fuel level. Typically this is an automotive type fuel gauge mounted in the dash panel of the vehicle.

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Capacitance Gauge Sender

Single tank fuel gauge senders are optimized for input signals between 200 and 800 pf.

The dual tank senders have a provision for connecting a crossover cable to use a single fuel gauge to display the sum of both fuel tanks on one fuel contents gauge. The dual tank sender is optimized for input signals between 500 and 2000 pf.

The standard connection to the vehicle is via a three pin Weatherpak female connector (pn 12010717). The connection to the vehicle tank is via a shielded cable and weathertight BNC connector. Other connectors are available upon request.

Sender with Gauge

Click on this link for sender part number information:

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Fuel Gauge Test Instrument

The test instrument enables the user to diagnose electrical problems with capacitance gauge wiring on both the LNG tank and the vehicle on which it is installed. The tester connects to the gauge circuit through the Weatherpak connector. It is powered by vehicle power or by an internal battery for tanks not installed on vehicles. It will detect open or short circuits, miscalibrated sending units, crossed wiring, and fuel gauge problems.

Fuel Gauge Test Instrument

999.017

Fuel Gauge Test Instrument

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Accessories

Accessories

990.002	3' RG-59U Crossover Cable
990.003	4' RG-59U Crossover Cable
990.004	8' RG-59U Crossover Cable
990.005	10' RG-59U Crossover Cable
318.001	VDO 301-029 Gauge 240-33 ohm   Plastic Case
990.001	Male Weatherpak Kit

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