Basic Tips On The Working Principles Of Pressure Sensors

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.

Besides the direct indicator of how much force is released from the fluid, other additional things can be indicated. For example, the fluid level or how fast it is flowing etc. Depending of the type of detection, the devices can be categorized as 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.

When it comes to the devices that use variable capacitance, these are made of two metal plates. Actually it is one metal plate and a metal diaphragm. When the force changes, the distance between the plates changes as well and this indicates the difference in pressure. Like the accelerometer, these devices are more stable than others but they do not function well in high temperature conditions. Also they are harder to assemble then the other types.

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.

Pressure sensors are devices that are very common in our days. They are used in many industrial domains. For example, they have a good role in the food industry. Regardless of their type, they are good tools for measuring the force generated by different fluids. But they also measure the fluid speed, the level of a fluid inside a container or many other valuable details.




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