The Way In Which Pressure Sensors Basically Work

By Adriana Noton


Pressure sensors are devices that are meant for measuring the pressure. The measuring applies to any liquid or gas. When the level of substance has reached a certain limit and has even passed over it, the device translates the force generated into an electric signal. This signal is interpreted by a computer and in this way the measurement is made.

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.

During the steam age the first devices were made and they became very popular. Since then, the technology has evolved a lot, and they have adapted. Their popularity is still the same in our times. They can be split in three categories depending on how they work: variable capacitance, strain gage and piezoelectric.

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.

Being made of quartz crystals, the piezoelectric sensors use the properties which are owned by these crystals from nature. They have this feature that allows them to make an electrical charge when they detect a force increase. The signal created must be amplified with the proper circuitry. They are not as resistant as other materials to vibration exposure or to any type of shock.

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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