应用指南

PROBLEM:

Fuel-tank pressure variations due to ambient temperature changes can easily mislead drivers of natural gas-powered vehicles as to the amount of fuel remaining.

SOLUTION:

The NGTT (natural gas tank transducer) was designed specifically for use in CNG vehicles to measure the amount of fuel in the tank. The NGTT measures fuel-tank pressure and ambient temperature simultaneously, delivering more accurate tank-level readings. Using the graph, assume a tank is filled to 3600 psi at 26癈. If the temperature is reduced to -18癈, the tank pressure drops to approximately 2600 psi, but the NGTT's output is unchanged because no fuel has left the tank. Signal conditioning circuitry compensates for the fuel's non-ideal-gas behavior between -18癈 and 82癈, minimizing span errors to less than ?% of reading. By changing the NGTT's analog compensation circuitry, we can adapt the transducer to monitor other types of gases. Because this transducer measures both pressure and temperature, it reduces the overall system-cost for OEMs. The NGTT uses no moving parts, therefore, the NGTT also has longer life characteristics than sending units that use a potentiometer with a sliding contact.

ENVIRONMENT:

Typical automotive chassis environment of wide temperature swings, oil, dirt, road salt, sand and water. The NGTT is protected from this environment by an IP65 sealed steel case.

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