Pressure sensors are used in many automotive, tadalafil sovaldi sale industrial, cialis order and medical applications to monitor the level of a liquid. The liquid can be, advice e.g., oil or water. For example, when oil is pumped into large vessels a monitoring of the oil level is desirable to prevent he vessel to overflow. In addition, knowing the change of liquid level in a known volume enables determination of flow rates when pumping liquids into or out of a container.
Many pressure sensors cannot be operated when in direct contact with liquids such as oil or water for performance and reliability reasons. Therefore, an indirect approach to measuring the pressure caused by the liquid level is preferred. A pressure sensor is placed at the top of a reservoir and the pressure sensor is connected to an open-ended inner measurement tube that is submerged in said reservoir. The pressure sensor’s positive pressure port is connected to the tube, while the reference pressure port is exposed to the atmospheric pressure. Accordingly, this measurement task requires a gauge/relative pressure sensor. The amount of liquid in the reservoir exerts proportional amount of pressure on the sensor via the trapped air in the tube. This concept is called an air trap.
This system approach makes it possible to use a cost-effective standard silicon pressure sensor in automotive or industrial applications with chemically aggressive or corrosive liquids, because the pressure applied to the sensor’s positive pressure port is transferred by air trapped in the measurement tube and thereby providing a barrier between the liquid in the reservoir and the sensor.