Pressure Sensor Bridge Configurations
Different pressure sensor bridge configurations: when each can and cannot be used.
The heart of Merit Sensor’s pressure sensors is a Wheatstone bridge that is comprised of a group of four resistors on a silicon etched diaphragm. As pressure is applied to the diaphragm the resistors are stressed, changing their resistance.
In an ideal setting, all of the resistors would be perfectly matched and completely temperature independent. In the real world, however, differences exist between the resistance values of each resistor. In addition, temperature also changes resistor values. The change to resistor values and the overall bridge output due to temperature is known as the Temperature Coefficient of Resistance, or TCR.
Many applications require that a pressure sensor operate independently of temperature. In these applications, the pressure sensor’s TCR must be compensated for. There are two general methods for TCR compensation – passive and active.
In passive compensation, the individual bridge resistor values will need to be measured in order to determine values needed for the compensation resistors.
In active compensation, a microcontroller, signal conditioner or analog circuit records the bridge output across various temperature and pressure conditions and adjusts sensor outputs accordingly.
