In electronic components, under otherwise constant conditions, the output signal will drift with temperature changes. To reduce this phenomenon, we use certain algorithms to correct the output result, thereby eliminating the influence of temperature changes on the component's output signal within a certain range. This method is called temperature compensation for electronic components, or simply "temperature compensation".
The static characteristics of most pressure sensors are closely related to ambient temperature. In practical applications, the operating temperature of the sensor varies greatly, and the heat output caused by these temperature changes is also significant. This can lead to substantial measurement errors, which in turn affect the static characteristics of the pressure sensor. Therefore, measures must be taken in the design to reduce or eliminate the measurement effects caused by temperature changes.
Pressure sensors convert changes in pressure into changes in resistance for measurement. Typically, the small signal output by a pressure sensor needs to be amplified by a subsequent amplifier before being transmitted to the processing circuit for pressure detection. Its resistance changes with pressure. In sensor applications, a series of specific technical measures are taken to ensure that the sensor's technical specifications and performance are not affected by temperature changes. This is called temperature compensation technology.
Most sensors are calibrated at a standard temperature of (20±5)℃, but their operating environment temperature can range from tens of degrees below zero to tens of degrees above zero. Sensors consist of multiple components. In particular, the static characteristics of sensitive elements made of metallic and semiconductor materials are closely related to temperature. The characteristics of components such as resistors and capacitors in the signal conditioning circuit remain largely unchanged with temperature. Therefore, effective measures must be taken to offset or reduce the impact of temperature changes on sensor characteristics. This means that temperature compensation for pressure sensors is essential.
1. Self-compensation method
Single-wire self-compensation method: This method enables the pressure sensor to self-compensate when the temperature changes by appropriately selecting the temperature coefficient and expansion coefficient of the grid wire, thereby reducing temperature error. This method is easy to manufacture and low in cost, but it is only applicable to specific specimen materials and has a narrow temperature compensation range.
Wheatstone Bridge Compensation Method: The Wheatstone Bridge Compensation Method is a commonly used temperature compensation method. It uses a strain gauge as one arm of a bridge and a compensator made of the same material as the strain gauge as the other arm, ensuring that the compensator and strain gauge exhibit the same temperature change pattern. When the temperature changes, the resistance of the two adjacent arms of the bridge changes simultaneously, but because their change patterns are identical, the bridge output is unaffected, thus achieving temperature compensation. Differential bridges, using two strain gauges of the same type with opposite strain directions, can directly compensate for temperature errors. The Wheatstone Bridge Compensation Method is simple and feasible; ordinary strain gauges can be used to compensate for various specimen materials over a wide temperature range.
2. Line compensation method
Circuit compensation is typically achieved by adding a temperature compensation circuit to the sensor's measurement circuit. When temperature changes cause a change in the sensor's output voltage, the temperature compensation circuit adjusts its output accordingly to counteract the effect of the temperature change on the sensor's output voltage. For example, when a temperature change increases the sensor's output voltage, the equivalent resistance of the temperature correction circuit increases, reducing the constant current source's output current, thereby reducing the sensor's output voltage and restoring it to its original value. The reverse is also true. This method can effectively eliminate errors caused by temperature changes and improve measurement accuracy.
3. Hardware compensation
Hardware compensation is primarily achieved by adding thermistors, leveling resistors, and other similar methods. For example, in MEMS piezoresistive pressure sensors, a thermistor can be added to monitor changes in ambient temperature and adjust the sensor's output signal accordingly to compensate for temperature errors. Alternatively, a dedicated ASIC integrated chip can be designed to achieve both low power consumption and temperature compensation.
4. Algorithm Compensation
Algorithm compensation is a method that uses software algorithms to process the output signal of a sensor to eliminate temperature errors. Commonly used algorithms include least squares linear fitting compensation, curve fitting compensation, and neural network-based compensation methods. These algorithms can establish mathematical models based on the sensor's output data at different temperatures, and then use these models to correct the actual measurement data to eliminate temperature errors.
