Wednesday, May 25, 2011

Fundamental Things About How Pressure Sensors 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.

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.

The construction of strain gages systems involves 2 things: a diaphragm and a strain gauge. The diaphragm is useful for the detection of the increasing force in the fluid. Then the information is passed to the strain gauge, which will generate a resistance equal to the force. The resistance can be measured with the aid of a DAQ or Data Acquisition System.

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 which is transmitted by the device is weak in the majority of cases. The measure unit is mV= 0,001 Volts. The voltage outputted depends on the force intensity. A voltage equal to zero means a pressure level that is zero (zero Bars). The signal does not exist in this case. But when the value is 5V the corresponding value will be 5 Bars.

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.




About the Author:



No comments:

Post a Comment