What’s the Difference Between a Pressure Transducer and a Pressure Switch? Simply put, the Pressure Transducer is a signal conversion and transmission device, and the pressure switch is a control switch device. This is the difference between a Pressure Transducer and a Pressure Switch. Let’s look at their differences in detail. And learn how to choose a pressure transmitter and pressure switch.
Difference Between a Pressure Transducer and a Pressure Switch
The Pressure Transducer uses the output as a standard signal, and is composed of a pressure-sensitive element and a conversion circuit. Using the pressure of the measured medium to produce a small change of current or voltage output on the pressure sensitive element.
The transmitter often needs to be used in conjunction with an external amplifier circuit to complete the process from pressure detection to control and display. Since the pressure sensor is a primary component, the signal fed back by the pressure sensor needs to be processed, analyzed, stored, and controlled by the measurement and control system. Make industrial automation equipment and engineering operation control more intelligent.
The pressure switch is a simple control device. When the measured pressure reaches the set value, it will automatically send out an alarm or control the function of turning on or off.
The pressure switch needs to be opened or closed under the set pressure. It can be used for simple control, and the output is the switch value.
The output of the pressure transmitter can be an analog signal or a digital signal. The post-processing is convenient, and it can also be converted into a standard transmitter signal for remote transmission.
Extended reading: NB-IoT Wireless Pressure Transmitter Networking Solution
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What is Pressure Switch?
A pressure switch is a mechanical switch that is activated by pressure to a set point. The switch is used to control a circuit by turning it on and off. Here the pressure point at which the switch is triggered is called the set point. The pressure threshold at which the switch is disabled is called the cut-off point. With enough force, the contacts can open or close the switch depending on their configuration.
This is a device that activates an electrical contact when a fixed fluid pressure is reached. Typically, this switch has two functions. The main function is to maintain the pressure or reservoir level of the system. The secondary function is to prevent equipment from operating at a lower efficiency or from being harmed. Its notation is as follows:
Structure of the pressure switch
The structure of the pressure switch mainly includes five parts. These are diaphragm, adjustment spring, lever, electrical contacts and terminals.
The diaphragm in this switch acts like a sensing element and is therefore used to detect pressure. This element is usually made of a pressure-sensitive, flexible material.
Adjusting the spring will change the set point or cut point, some switches have separate springs that control the set point and cut point.
The AUTO/OFF lever is used to manually activate or deactivate the switch, this lever is very helpful to turn off the switch throughout the installation or maintenance process. Sometimes, a knob is used instead of a lever, but the principle works the same.
The electrical contacts allow current to flow through them once they are contacted by an external power source.
The terminals of the switch are used to connect an external power source to the contacts.
A pressure switch works by operating an electrical contact once a fixed fluid pressure is reached. The switch will make electrical contact when the pressure increases or the pressure decreases from a fixed preset pressure level.
Type of pressure switch
There are two types of pressure switches on the market today, mechanical and electronic.
Mechanical pressure switches are the most widely used due to their lower cost and ease of use compared to electronic pressure switches. These switches can be equipped with a mechanical pressure sensing element that deforms in response to fluid pressure. The different types of mechanical pressure switches are discussed below.
- Piston pressure switch
This type of switch is the most popular and is widely used in different applications. Once the pressure of the fluid changes, it moves the piston axially, which triggers the switch. The switch can directly or indirectly detect the pressure of the liquid. Therefore, direct inspection mainly involves seals like O-rings. to prevent liquids from entering the components. Whereas indirect detection mainly involves a flexible diaphragm that separates the piston from the fluid. - Diaphragm pressure switch
This is a high quality switch primarily developed for safety critical applications. The main benefit of diaphragm pressure switches is that no voltage supply is required for the switching process. The switch consists of a metal membrane that is directly connected to the soaker portion of the switch and the diaphragm that activates the switch. The switch is used for monitoring process pressure and control in different industries such as chemical, petrochemical, natural gas, oil etc. - Bourdon tube pressure switch
This is an elastomer or flexible metal tube that attaches to one end of the switch while leaving the other end free to move. Once the pressure of the liquid in the tube rises, it tends to level, and this movement is then used primarily to activate the switch. These switches are suitable for different applications such as chemical, general power stations and petrochemical as long as the operating force is medium to high. - Differential pressure switch
This switch is useful when evaluating the force between two points within a system simply connected to two process ports on the upper or lower part of the device. If the pressure difference between the two sides increases by a certain threshold, the switch can be triggered. These switches are suitable for monitoring pressure drops in screens, filters and tank levels. - Electronic pressure switch.
It can be used with pressure sensors such as strain gauges. These types of switches have analog capabilities, so they are not limited to an on or off position. Continuous and variable signals can also be transmitted for more precise monitoring. Therefore, these are not only switches, but also measuring instruments or transmitters. Some additional features of these electronic switches are field programmability of switching functions, time delays, hysteresis, set points, etc.
What is Pressure Transducer?
A pressure transducer is a device that converts pressure into a pneumatic signal or an electric signal for control and remote transmission.
It can convert the physical pressure parameters such as gas and liquid felt by the load cell sensor into a standard electrical signal (such as 4~20mADC, etc.). It can be used to supply secondary instruments such as indicating alarms, recorders, and regulators for measurement and indication, and process regulation.
Working Principle of Pressure Transducer
Pressure Transducer Electrical components that feel pressure are generally resistance strain gauges. The resistance strain gauge is a sensitive device that converts the pressure on the device under test into an electrical signal. The most widely used strain gauges are metal resistance strain gauges and semiconductor strain gauges.
There are two types of metal resistance strain gauges: wire strain gauges and metal foil strain gauges. Usually, the strain gauges are tightly bonded to the mechanical strain-generating substrate through a special adhesive. When the stress of the substrate changes, the resistance strain gauge also deforms together. Change the resistance value of the strain gauge, so that the voltage applied to the resistance changes.
Read more about: The Difference Between Absolute And Gauge Pressure
Types of Pressure Transducers
The types of pressure transmitters are roughly as follows: resistance strain gauge pressure transmitters, semiconductor strain gauge pressure transmitters, piezoresistive pressure transmitters, inductive pressure transmitters, capacitive pressure transmitters, Resonant pressure transmitter and capacitive acceleration sensor, etc.
Piezoresistive pressure transmitter
The resistance strain gauge is a sensitive device that converts the strain change on the tested object into an electrical signal. It is one of the main components of piezoresistive strain transmitters. There are two kinds of resistance strain gauges, metal resistance strain gauges and semiconductor strain gauges.
Usually, the strain gauges are tightly bonded to the substrate that generates mechanical strain through a special adhesive. When the stress of the substrate changes, the resistance strain gauge also deforms together. Change the resistance of the strain gauge. This changes the voltage across the resistor.
Ceramic pressure transmitter
Principle Corrosion-resistant pressure transmitters have no liquid transfer, and the pressure acts directly on the front surface of the ceramic diaphragm. To make the diaphragm slightly deformed, thick film resistors are printed on the back of the ceramic diaphragm and connected to form a Wheatstone bridge.
Due to the piezoresistive effect of the varistor, the bridge produces a highly linear voltage signal proportional to the pressure and proportional to the excitation voltage. The standard signal is calibrated as 2.0 / 3.0 / 3.3 mV/V according to different pressure ranges. Compatible with strain gauge sensors.
Through laser calibration, the sensor has high temperature stability and time stability. The sensor comes with a temperature compensation of 0-70°C, and can be in direct contact with most media. ,
Diffused silicon pressure transmitter
The pressure of the measured medium acts directly on the diaphragm of the sensor, causing the diaphragm to produce a micro-displacement proportional to the pressure of the medium. The resistance value of the sensor is changed, and the change is detected by the electronic circuit. And convert and output a standard measurement signal corresponding to this pressure.
Piezoelectric Pressure Transmitters
The piezoelectric materials mainly used in piezoelectric sensors include quartz, potassium sodium tartrate, and ammonium dihydrogen phosphate. Among them, quartz is a natural crystal in which the piezoelectric effect is found. Within a certain temperature range, the piezoelectric properties always exist, but when the temperature exceeds this range, the piezoelectric properties disappear.
Capacitive pressure transmitter
Ceramic capacitive sensors are available for measurements in normal or aggressive media. Materials such as gas, gas or liquid, but not prone to precipitation, crystallization or stiffening are recommended. Applied to tank liquid level measurement, sea water, water on board, diesel oil, waste oil.
Selection of pressure switch and pressure transmitter
Both pressure switches and pressure transmitters are intelligent digital display pressure measurement products integrating pressure measurement, display, output and control. When choosing, you only need to remember the following 6 points to know what kind of pressure switch and pressure transmitter to use.
According to the characteristics of pressure switch and pressure transmitter, you can start from the following data that need to be measured:
- The measured medium and the actual condition of the medium
- The measured pressure range
- Required measuring range
- The temperature of the working conditions on site
- The connection method used in conjunction with the working conditions
- Installation location
According to the above 6 points of data and requirements, you can know what kind of pressure switch or pressure transmitter is needed. In addition, pressure switches and pressure transmitters are all non-standard customized products. It can be used according to the site Working conditions to decide.
More Featured Pressure Measurement Solutions
Sino-Inst is a manufacturer of Pressure Transducer and a Pressure Switch. We produce and sell all kinds of automatic measurement and control instruments and meters. The main products are: hydraulic pressure sensor, liquid level/water level sensor, Miniature Pressure Sensor/Transducer, micro pressure/negative pressure/vacuum pressure sensor, temperature transmitter, load cell and other pressure, differential pressure, liquid level, temperature , weighing sensors and various special pressure sensors and intelligent control systems.
Pressure Transducer and a Pressure Switch are commonly used instruments in industrial production process. The pressure switch turns the switch on or off at your given pressure. The output of the pressure sensor can be an analog signal or a digital signal, which is convenient for subsequent processing, and can also be converted into a standard transmitter signal for remote transmission.
If you need to purchase a Pressure Transducer and a Pressure Switch, or have any technical questions about Pressure Sensor/Transducer, please feel free to contact our engineers.
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Wu Peng, born in 1980, is a highly respected and accomplished male engineer with extensive experience in the field of automation. With over 20 years of industry experience, Wu has made significant contributions to both academia and engineering projects.
Throughout his career, Wu Peng has participated in numerous national and international engineering projects. Some of his most notable projects include the development of an intelligent control system for oil refineries, the design of a cutting-edge distributed control system for petrochemical plants, and the optimization of control algorithms for natural gas pipelines.