| 摘要 |
A measuring device (2) for testing a liquid (4) used as reducing agent in connection with exhaust cleaning for exhaust gases from a combustion engine. A temperature sensor (6) measures the temperature in the liquid. An acoustic velocity measuring unit (8) measures the acoustic velocity in the liquid. The measured first temperature T1 for the liquid and a first acoustic velocity v1 for the liquid at the temperature T1 are delivered to a calculation unit (10). The temperature sensor determines a second temperature T2 for the liquid and delivers a temperature signal (12) to the calculation unit (10). That unit calculates the absolute value of a temperature difference &Dgr;T between T1 and T2, i.e. &Dgr;T=|T1−T2, and compares &Dgr;T with a predetermined threshold value TTH. If &Dgr;T exceeds TTH, the acoustic velocity measuring unit (8) determines a second acoustic velocity v2 for the liquid at the temperature T2 to deliver an acoustic velocity signal (14) to the calculation unit (10), which compares v1 and v2 with reference values vref1 and vref2 for a reference liquid at the respective temperatures T1 and T2. An approved indicating signal (18) is generated if the measured values v1 and v2 are within approved velocity ranges, but not approved if v1 and v2 are not within those ranges. |
