Electrical Pressure Transducer
Electrical pressure transducers use electrical circuit to convert the motion produced by the mechanical pressure elements into changes in electrical values. These values can then be measured to indicate pressure.
Most electrical transducers require an outside voltage source. Basically this type of transducer has a voltage applied to a circuit. Current output varies in direct proportion to an input variables such as changes in pressure.The changes in current flow are measured and indicate pressure.
A potentiometric consists of a wire wound resistor with removable slide attached to it. Moving the slide will change the amount of resistance of the potentiometer. When the potentiometer is connected in an electronic circuit any movement of the slide on the potentiometer will change the resistance in the circuit. The circuit configuration most often used to make accurate measurement is the Wheatstone bridge.
In a Wheatstone bridge,the bridge has two parallel legs. Each leg has two resistors in series.A voltage source has connected to the bridge so that current will follow through each leg. In a typical bridge,there is another circuit installed here.When the resistance of all four resistor is exactly equal the current flow through each leg is equal. In this condition,the bridge is balanced. However,if one of these resistors is changed,current flow through each leg is no longer equal.
If an instrument is installed,the current flow through this circuit is measured.in other words,we can determine the amount of unbalance in the bridge. In pressure measuring instruments one of these resistors is replaced with a resistor that is exposed to the changes in process pressure. When there is no process pressure,the bridge is balanced and there will be no current flow through the instrument.However if pressure changes,the resistance of the resistor exposed to the pressure will change and current will flow through the instrument indicating pressure.