Pressure switches and pressure sensors are both devices used to detect pressure. However, they differ significantly in their functions, operating principles, and application scenarios.
Understanding Pressure Switch vs Sensor can help you choose the most suitable product.
First, for us, the main difference between pressure switches and pressure sensors lies in their functions.
A pressure sensor converts the pressure of an object into an electrical signal for display and control system connection. This sensor has a continuous output and is typically connected to a controller that monitors and responds to pressure.
A pressure switch, on the other hand, opens or closes when pressure reaches or exceeds a preset value. It is designed to open or close a circuit when pressure within a system increases or decreases.
What is a pressure switch? How does it work?
A pressure switch is a type of switch that uses a preset pressure level. When the measured medium reaches this pressure level, the switch automatically opens or closes. A pressure switch must be pre-set to a pressure value before it opens or closes. It is used for simple control and has a digital output.
A pressure switch senses the pressure of the medium using an elastic element, such as a bellows, diaphragm, or spring tube. When the pressure reaches the preset value, the elastic element deforms, driving a mechanical linkage. This triggers the microswitch contacts, thus controlling the circuit. The switch resets after the pressure returns to normal.
What is a pressure sensor? And how does it work?
A pressure sensor converts the pressure applied by a measured object into a corresponding electrical signal and then outputs it. In industrial production, it is primarily used to monitor and control fluid pressure changes in real time.
Unlike pressure switches, pressure sensors can output continuously changing analog signals. They are widely used in precision control and monitoring.
A pressure sensor consists of a sensing element, signal processing circuitry, and an output interface. When pressure acts on the pressure-sensitive element, it deforms accordingly. This is converted into an electrical signal, which is processed by a transmitter circuit and then output. Users can simply read the pressure value based on the numerical value represented by the output electrical signal.
Pressure Switch vs Sensor
Next, let’s comprehensively compare the differences between the two.
| Item | Pressure Switch | Pressure Sensor |
| Function | A pressure switch outputs a switching signal when the pressure reaches a set value. | Pressure sensors convert pressure into an electrical signal. They can display real-time pressure values and have a continuous output, typically connected to a controller that monitors and responds to pressure. |
| Application | Pressure switches are suitable for controlling and protecting simple devices or systems. | Pressure sensors are suitable for high-precision control systems that continuously monitor pressure. |
| Output Signal | A pressure switch outputs a switching signal, indicating either an on or off state. Specifically, pressure switches can have either an NPN or PNP output signal. | The output signal of a pressure sensor is a continuously varying electrical signal that represents the pressure of the measured medium. Examples include 4-20mA and 0-5V. |
| Varies in Accuracy and Range | Pressure switches typically have low accuracy and a small measuring range. | Pressure sensors can have high accuracy of 0.1%FS and a wide measurement range. |
| Cost | Pressure switches have simple functions and are generally inexpensive. | Pressure sensors are generally more expensive than pressure switches. Pressure sensors have internal signal conditioning circuitry, resulting in higher measurement accuracy and easier signal processing. |
Oil Pressure Switch vs Sensor
Oil pressure sensors are specifically designed to measure oil pressure in liquids and are typically used in lubrication and hydraulic systems. These systems require adequate oil pressure to lubricate mechanical components or perform tasks. Oil pressure sensors output the detected oil pressure as a continuous electrical signal, which can be displayed on a secondary instrument in real time.
An oil pressure switch is an automatic control component that opens or closes an electrical circuit based on pressure changes. When the system pressure reaches a set value, the oil pressure switch activates, closing or opening the circuit. This provides protection, monitoring, and control functions for mechanical equipment.
FAQ
When selecting a setting range, users must consider the maximum system pressure the pressure switch will withstand. The pressure switch’s switching point setting range is typically smaller than the pressure switch’s overload safety limit. This means that pressure spikes can be absorbed.
This is important, for example, for protecting pumps from dry-running. In these conditions, the system pressure can be many times higher than the pressure switch’s switching point. The relatively small range is due to the particularly sensitive measuring element, which ensures high repeatability. Therefore, larger switching values and overpressure ranges require a more robust diaphragm, which compromises repeatability.
There are many different types of pressure switches, suitable for different applications.
Here are some key pressure switch types:
1. Differential Pressure Switch
A differential pressure switch detects the difference in pressure between two set points. If the pressure drops or exceeds a predetermined value, an alarm is triggered, opening or closing a circuit.
Differential pressure switches are often used for preventative maintenance. Typical applications may include energy conservation, purification, and monitoring air filters and ventilation flow.
2. Hydraulic Switch
Hydraulic switches are frequently used in the automotive and aerospace industries. A typical example of their use is to alert the driver to the fuel level in the vehicle.
3. Pneumatic Switch
Pneumatic switches are designed to detect increases or decreases in air pressure within pneumatic systems. Includes adjustable and non-adjustable units for pressure and vacuum applications.
In manufacturing and hydraulic systems, they are commonly used to automatically monitor pressure in compressed air systems.
4. Digital Pressure Switch
Digital pressure switches digitally display pressure values and output a switching signal. Digital pressure switches are available in adjustable and non-adjustable formats, offering greater flexibility and programmability.
Over time, pressure switches experience wear and tear. Frequency of use, temperature, and installation environment all affect their lifespan.
We regularly inspect the switch to determine if there are any issues or if replacement is necessary. The following steps are provided for your reference:
- Identify the pressure switch and disconnect it.
- If necessary, remove the switch cover to gain access to the terminals.
- Set a multimeter to the ohms (Ω) setting.
- Touch the multimeter leads to each switch terminal.
- If the reading is 0, the switch is closed and operating properly. However, if this is not the case, the pressure switch may be faulty and requires further investigation.
More Pressure Measurement Solutions
Using a pressure transmitter or pressure switch enables precise closed-loop control. For example, an oil pressure switch monitors engine oil pressure and issues a warning when oil pressure is abnormal, protecting the engine from damage.
Pressure sensors and pressure switches differ in their functions, operating principles, and applications, and are not interchangeable. In actual applications, the appropriate device should be selected based on specific needs.
If you need to select a pressure switch or pressure transmitter, please feel free to contact our sales engineers!