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Wednesday, May 25, 2011

The Way In Which Pressure Sensors Basically Work

By Adriana Noton


Pressure sensors are very popular in our times as they are the best systems for measuring pressure when it comes to fluid substances. When a container is full of liquid, for instance, and more liquid is released in the container, the sensor detects the increase in force and transforms it into an electric charge. After the transformation, the signal obtained will be transmitted further to the interpreter device. This is how equipment like this is functioning.

The force parameter is not the only one measured; there are also secondary measurements like the substance amount or the flow of the liquid/gas. These devices can measure a lot of things. The reading can be either static or dynamic.

Since the steam age, these equipments were very much used and demanded. And were used until now, when they have the same popularity. They can be categorized through the functioning principles in three types: strain gage, piezoelectric and variable capacitance.

The pressure sensor can be found in different shapes and designs; they can be classified after performance or price, after the range of measurement and the temperature range of use. There are some dynamic sensors that can measure rapid changes in speed or pressure, these ones have a high performance and are made of quartz.

Strain gage devices are constructed from 2 parts: the diaphragm and the strain gauge. When the force created by the fluid increases, the diaphragm detects the modification and it sends a signal to the strain gauge. Now the strain gauge will resist the force. Then the resistance force generated will be measured by a Data Acquisition System or DAQ.

The variable capacitance modules have two metallic elements. The first element is a metal plate and the second is a metal diaphragm. The distance from the plate to the diaphragm determines the detection of any physical force. Like the accelerometer, devices of this construction are very stable; the only disadvantage is the resistance to high temperatures. It is also more difficult to assemble this type.

The piezoelectric systems have a construction layout that is based on quartz crystals. The quartz has a natural property which makes it create electrical charges at the detection of strong forces. The signal has to be boosted after it is generated. Their disadvantage is low resistance to vibrations and shocks.

The signal obtained from the sensors is usually small and it can be measured in mV (a thousand parts is one Volt). The range of Volts that is outputted from the device is related to the amount of physical force which generates the current. For instance, zero Volts mean zero force. In this point no electrical signal is sent to the interpreter. The maximum range limit can be, for instance 5V, case in which a pressure of 5 Bars is generated.

Nowadays pressure sensors have a very high range of use, they are commonly used in the food industry, for example. With no exceptions, they have the role of measuring the forces made by the fluids. They are also able to detect the flow and the fluid level.




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