Physical principle and pressure pattern
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The physical principle is based on the ideal gas law:
Pressure and temperature have a direct proportional relationship when quantity and volume remain constant .
The NVLD uses this physical principle to identify leaks in the fuel evaporation system.
This means that a vacuum forms when the temperature in the fuel tank drops. The NVLD uses a temperature sensor to measure the temperature. The NVLD uses the diaphragm-operated pressure switch to determine the vacuum. This diaphragm switches the pressure switch at a certain vacuum/ambient pressure combination.
The following graphic demonstrates the temperature profile and pressure pattern both when there is a leak in the fuel tank and when there is no leak.
| Index | Explanation |
|---|---|
| A | Pressure pattern without leak |
| B | Pressure pattern with leak |
| 1 | Pressure |
| 2 | Temperature |