The temperature compensation mechanism of vacuum pressure switches

The temperature compensation mechanism of vacuum pressure switches is mainly to counteract or weaken the influence of temperature changes on the sensor characteristics and ensure its measurement accuracy. Common methods include hardware compensation and algorithm compensation:

Hardware compensation

Self-compensation method

Single wire self-compensation method: Appropriately select the temperature coefficient and expansion coefficient of the grid wire to enable the pressure sensor to self-compensate when the temperature changes, thereby reducing the temperature error. This method is easy to process and has a low cost, but it is only applicable to specific test materials and has a relatively narrow temperature compensation range.

Combined self-compensation method: It is composed by connecting two metal wires with different temperature coefficients in series. One type is to select two metal wires with different resistance temperature coefficients. Another type is to use two metal wires with the same symbol of resistance temperature coefficient, but the resistances formed by the two metal wires are respectively connected to the adjacent two arms of the bridge.

Line compensation method

Bridge compensation method: Use a strain gauge as one arm of the bridge, and a compensation gauge made of the same material as the strain gauge as the other arm of the bridge, so that the compensation gauge and the strain gauge have the same temperature change law. Compensation is carried out based on the characteristic that when the resistance of the adjacent two arms of the bridge changes by a certain amount simultaneously, it will not affect the output of the bridge. The differential bridge can directly compensate for temperature errors because it uses two strain gauges of the same type, but their strain directions are opposite. The bridge compensation method is simple and feasible. By using ordinary strain gauges, various specimen materials can be compensated within a wide temperature range, and thus it is the most commonly used.

Adding thermistors and leveling resistors: In the sensor measurement circuit, a temperature compensation circuit is added. For instance, in a MEMS piezoresistive pressure sensor, a thermistor is added to monitor changes in the ambient temperature, and the output signal of the sensor is adjusted accordingly to compensate for temperature errors.

Algorithm compensation: The output signal of the sensor is processed through software algorithms to eliminate temperature errors. Commonly used algorithms include neural network-based least square fitting for straight line compensation, curve fitting compensation, etc. These algorithms can establish mathematical models based on the output data of the sensor at different temperatures, and modify the actual measurement data through this model to eliminate temperature errors.