The reasons for the delayed response of vacuum pressure switches

The response delay of the vacuum pressure switch may be caused by the following reasons, which need to be investigated one by one in combination with the system characteristics:

Mechanical structure and medium characteristics

Elastic element hysteresis

There is a deformation lag in the diaphragm or spring inside the switch when the pressure changes. For instance, in rapid pressure fluctuations, metal diaphragms experience action delays due to the time required for the elastic recovery of the material.

Analogy: Similar to a spring mattress that slowly bounces back when subjected to force.

Medium viscosity

If the measured medium is a high-viscosity fluid (such as lubricating oil), the pressure transmission speed will be reduced due to the decrease in medium resistance, resulting in a lag in the switch response.

The speed of pressure transmission between mercury and water is significantly different, with the former being faster.

Pipeline volume effect

If the pressure tapping pipe is too long or the pipe diameter is too large, it will increase the medium filling time. For instance, in a 1-meter-long φ6mm pipe, it takes several seconds for the medium to fully transmit the pressure signal when the pressure changes.

2. Electrical and Signal Processing

Contact action time

There is a physical contact delay when mechanical contacts close or open, usually in the millisecond range, but it may affect accuracy in high-frequency response scenarios.

Comparison: Solid-state relays have no mechanical contacts and have a faster response speed.

Signal filtering and damping

The built-in damping device of the switch (such as damping holes) can filter out pressure fluctuations, but it will prolong the response time. For example, to suppress the pressure spikes when the pump starts and stops, the damping time is usually set at 0.5 to 2 seconds.

Circuit processing delay

Circuit processing such as converting analog signals to digital signals, signal amplification or filtering will introduce delays, especially in low-power design, which may be more obvious.

3. Environmental and installation factors

The influence of temperature

In a low-temperature environment, elastic elements (such as rubber diaphragms) harden, resulting in a slower response. High temperatures may cause the medium to expand or change in viscosity, indirectly affecting pressure transmission.

Data: The response time of a certain model of switch at -20℃ is 30% longer than that at 25℃.

Improper installation location

If the switch is installed in an area with severe pressure fluctuations (such as the pump outlet), the pressure signal may be distorted due to the inertia of the medium. In such cases, a buffer device needs to be added or the installation point adjusted.

Leakage and Sealing

Leakage of the switch body or the pressure tapping port will cause attenuation of the pressure signal, which is manifested as a slow response. For example, a tiny leakage may cause the pressure to drop from -90 kpa to -85 kpa within several seconds.

4. Design and selection issues

The range does not match

If the switch range is much larger than the actual pressure variation range (for example, using a -100 to 0kPa switch to monitor -10 to 0kPa), the sensitivity will decrease and the response time will increase.

Suggestion: Select a switch with a range of 1.5 to 2 times the actual pressure.

The damping setting is too large.

To avoid misoperation, some switches provide adjustable damping function. If the damping time is set to 3 seconds, there will be no response to pressure fluctuations shorter than this time.

Aging and wear

After long-term use, diaphragm fatigue, weakened spring elasticity or contact oxidation can all lead to a slower response. For example, the response time of the switch after five years of use may be 50% longer than that of a new switch.

Suggestions for investigation and optimization

Shorten the pressure extraction pipeline: Reduce the length and volume of the pipeline, and give priority to using hard pipes (such as stainless steel) instead of hoses.

Select the appropriate range: Avoid insufficient sensitivity caused by an overly large range.

Adjust the damping setting: Balance the response speed and anti-interference capability based on the actual working conditions.

Regular maintenance: Check sealing, clean contacts, and replace aged parts.

Environmental control: Avoid extreme temperatures and increase insulation or heat dissipation measures if necessary.