A basic resistive pressure sensor, often called a resistive pressure transducer or strain gauge pressure sensor, is a device used to measure pressure by utilizing the change in resistance of a strain-sensitive element in response to applied pressure. Here's how it generally works:
Strain-Sensitive Element: The core of a resistive pressure sensor is a strain-sensitive element, often a metal or semiconductor material, like a strain gauge. This material changes its resistance when subjected to mechanical strain. When pressure is applied to the sensor, the strain-sensitive element deforms slightly, causing its resistance to change.
Wheatstone Bridge Configuration: To measure this change in resistance accurately, the strain-sensitive element is often connected in a Wheatstone bridge configuration along with other resistors. A Wheatstone bridge is a circuit arrangement that helps amplify the small changes in resistance. It consists of four resistors arranged in a diamond shape, and the strain-sensitive element forms one of the arms of the bridge.
Voltage Supply: A voltage supply is connected across the Wheatstone bridge circuit. When no pressure is applied and the strain-sensitive element has no deformation, the bridge is balanced, and the output voltage across the bridge is zero.
Pressure Application: When pressure is applied to the sensor, the strain-sensitive element undergoes deformation due to mechanical stress. This deformation leads to a change in its resistance. This, in turn, causes the Wheatstone bridge to become unbalanced, generating a differential output voltage across the bridge.
Output Measurement: The output voltage is typically very small, so it's amplified by signal conditioning circuitry. This amplified voltage can be read and processed by analog or digital electronics, such as microcontrollers or measurement instruments. The magnitude of the output voltage change is proportional to the applied pressure, allowing for pressure measurement.
Calibration: Since the relationship between the change in resistance and the pressure can be non-linear or have temperature dependencies, resistive pressure sensors often require calibration to convert the output voltage into meaningful pressure readings. This calibration involves mapping the sensor's response to known pressure values.
Resistive pressure sensors are widely used in various applications, such as industrial automation, automotive systems, medical devices, and consumer electronics, where relatively accurate pressure measurements are required. Keep in mind that there are many different designs and variations of resistive pressure sensors, each suited for different pressure ranges, accuracy levels, and environmental conditions.