Repeatability accuracy analysis of vacuum pressure switches

Definition of repeatability accuracy

Repeatability accuracy refers to the degree of consistency of the output results of a vacuum pressure switch when it measures or operates the same pressure value multiple times under the same working conditions. In simple terms, it refers to the magnitude of the difference between the output signals or action points of a switch when it repeatedly measures or controls the same pressure point. The smaller the difference and the higher the repeatability accuracy, the more stable and reliable the performance of the switch is.

Factors affecting repeatability accuracy

Sensor performance

Sensitivity: Sensors with high sensitivity can sense pressure changes more accurately. If the sensor's sensitivity is insufficient, it may not be able to accurately detect even minor pressure fluctuations, resulting in deviations at the trigger points of each measurement or action, thereby reducing the repeatability accuracy. For instance, when measuring low vacuum pressure, a sensor with low sensitivity may respond sluggishly to minor changes in pressure, resulting in inconsistent pressure values at which the switch operates in different measurements.

Linearity: The ideal sensor should have a linear relationship between the output and input pressure. If the linearity of the sensor is poor, its output characteristics will change at different pressure ranges. This will cause the corresponding relationship between the output signal and the pressure of the switch to be unstable during repeated measurements, affecting the repeatability accuracy. For instance, when the pressure is low and high, the output deviation of the sensor may be different, resulting in inconsistent switch action points.

Hysteresis: Hysteresis refers to the difference in output signals corresponding to the same pressure value during the pressure increase and decrease processes of the sensor. This difference will cause the pressure values at which the switch operates during the pressure rise and fall processes to be different, thereby reducing the repeatability accuracy. For example, when the pressure gradually increases from low to high, the switch may act at a certain pressure value; When the pressure gradually decreases from high to low, the switch may act at another different pressure value.

2. Mechanical structure

Elastic elements: The elastic characteristics of elastic elements (such as diaphragms, bellows, etc.) will directly affect the repeatability accuracy. If the elasticity of the elastic element is unstable, after being subjected to multiple pressure changes, its deformation recovery ability will change, resulting in inconsistent pressure values at the switch action point. For instance, the diaphragm may experience fatigue and weakened elasticity after long-term use, which leads to a decrease in the operating pressure of the switch during repeated measurements.

Mechanical transmission components: The clearance and wear of mechanical transmission components (such as levers, gears, etc.) can also affect the repeatability accuracy. The gap can cause movement during the transmission process, making the trigger point of the switch action unstable. Wear and tear will change the size and shape of the components, affecting the accuracy of pressure transmission and thereby reducing the repeatability accuracy. For instance, if there is a gap at the connection of the lever, under the action of pressure, the swing amplitude of the lever will be different, resulting in inconsistent pressure values for the switch action.

3. Environmental factors

Temperature: Temperature changes can affect the performance of sensors and elastic elements. An increase or decrease in temperature will cause changes in parameters such as the resistance and capacitance of the sensor, thereby affecting the accuracy of the output signal. The elastic modulus of the elastic element also changes with temperature, resulting in a change in the pressure value at the switch action point. For instance, in high-temperature environments, the sensitivity of the sensor may decrease, and the elasticity of the elastic element may weaken, resulting in a decline in the repeatability accuracy of the switch.

Humidity: Excessive humidity may cause the sensors and circuit boards to get damp, affecting their electrical performance. For some vacuum pressure switches that use electronic components, changes in humidity may cause problems such as leakage and short circuit, resulting in unstable output signals and reduced repeatability accuracy.

Vibration: External vibration can cause slight displacement of the mechanical components inside the switch, affecting the accuracy of pressure measurement and operation. Long-term vibration may also cause components to loosen or get damaged, further reducing the repeatability accuracy. For instance, in an industrial environment with significant vibration, the measurement results of switches may fluctuate greatly.

4. Electrical components

Circuit stability: The performance stability of the circuit components inside the switch (such as resistors, capacitors, integrated circuits, etc.) will affect the accuracy of the output signal. If there are problems such as parameter drift and noise interference in the circuit components, it will lead to unstable output signals, thereby reducing the repeatability accuracy. For instance, the resistance value varies with temperature, which will cause the gain of the circuit to change and affect the magnitude of the output signal.

Power supply stability: Fluctuations in power supply voltage will directly affect the working performance of the switch. Unstable voltage can cause changes in the working state of sensors and circuit components, thereby affecting the accuracy of the output signal. For instance, a decrease in the power supply voltage may cause the sensor's sensitivity to decline, resulting in inaccurate pressure values for the switch's operation.

Methods for improving repeatability accuracy

Optimize the selection of sensors

Select sensors with high sensitivity, good linearity and low hysteresis. When purchasing sensors, it is required that suppliers provide detailed technical parameters and performance test reports to ensure that the sensors meet the accuracy requirements of vacuum pressure switches.

2. Improve the mechanical structure design

Optimize the material and structure of the elastic element to enhance its elasticity and stability. For instance, diaphragms are made of alloy materials with high strength and high elasticity to reduce elastic fatigue.

Reduce the clearance of mechanical transmission components, adopt high-precision processing techniques and assembly methods, and ensure the fit accuracy between components. At the same time, regular maintenance and upkeep of mechanical components should be carried out, and worn parts should be replaced in a timely manner.

3. Control environmental factors

For environments with significant temperature variations, temperature compensation measures can be adopted, such as integrating a temperature sensor inside the sensor and compensating for errors caused by temperature through software algorithms.

In an environment with high humidity, a sealed design can be adopted to prevent the interior of the switch from getting damp. At the same time, install dehumidification equipment to reduce the environmental humidity.

For environments with significant vibration, shock-absorbing measures such as installing shock-absorbing pads and shock absorbers can be adopted to reduce the impact of external vibration on the switch.

4. Ensure the performance of electrical components

Select electrical components with reliable quality and stable performance, and conduct strict screening and testing. In circuit design, anti-interference measures such as filter circuits and shielding measures are adopted to reduce noise interference.

Equip a stable power supply, such as using a voltage stabilizer or UPS uninterruptible power supply, to ensure the stability of the power supply voltage. At the same time, regular monitoring and maintenance of the power supply should be carried out to promptly identify and solve power supply issues.