Comparison of pressure sensors, relays and switches
We all often hear about pressure sensors, pressure relays and pressure switches. Are they connected and what is the difference? The following is a detailed introduction of the three.
The pressure sensor is composed of a pressure-sensitive element and a conversion circuit, which uses the pressure of the measured medium to act on the pressure-sensitive element to produce a small change in current or voltage output. The sensor 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, so that industrial automation equipment and engineering operation control are more intelligent.
The pressure relay is a hydroelectric switch signal conversion element that uses liquid pressure to open and close electrical contacts. When the system pressure reaches the set pressure of the relay, it sends out electrical signals to control the actions of electrical components, realizes the load or discharge control of the pump, the sequential action of the actuators, the safety protection and interlock of the system, etc. It is composed of two parts: pressure-displacement conversion component and micro switch. According to the structure type of the pressure-displacement conversion component, there are four types: plunger type, spring type, diaphragm type and bellows type. The plunger structure is divided into two types: single plunger and double plunger. The single plunger type can be divided into three types: plunger, differential plunger and plunger-lever. According to the contacts, there are single contacts and double contacts.
The pressure relay actually belongs to the category of pressure switches. Its output is a contact signal, but it is mostly used in hydraulic systems. It is customarily called pressure relay in the industry (in fact, there may not be a conventional concept relay or multiple contacts, but it may Just a single pair of contacts, such as micro switches). The output contact pressure value can be adjusted. Pressure relays are generally more specific.
The pressure switch is a functional switch that automatically turns on or off when the set value is reached according to the set pressure.
The pressure switch is a device that can output contact signals or high and low potential signals when it is higher or lower than the set pressure (pressure) value. The main components are pressure sensing elements and output devices. The output devices can be passive contacts (contacts), or they can be composed of electronic circuits that can output contacts or high and low potential signals (power supply required). The medium can be gas or liquid.
Generally, there are only one pair of contacts (normally open or normally closed), and two pairs are also available. Pressure switches that output high and low potential signals have 4-wire systems and 3-wire systems.
Pressure switches and pressure relays can only open or close the switch under your given pressure for simple position control. They are all on-off output! Pressure relays can provide more output nodes or node types than pressure switches. The output of the pressure sensor can be an analog signal or a digital signal, which is convenient for subsequent processing, and can also become a standard transmitter signal for remote transmission.
The pressure sensor is the most commonly used sensor in industrial practice. It can sense pressure and convert it into a usable output signal. The pressure switch opens or closes the system under a certain pressure to detect, display, alarm and detect the pressure signal of the medium. Control signal output to ensure normal operation of the system. Then the pressure sensor and the pressure switch act as pressure-related instruments at the same time.
The pressure switch is a kind of switch as its name implies, but this kind of switch is a pressure set in advance, when the measured medium reaches this pressure, the switch can be automatically turned on or off. The pressure switch must be given a pressure value in advance, and then the switch is turned on or off. It is used for simple control, and it is all on-off output.
The pressure sensor can output not only analog signal, but also digital signal output, digital signal processing is more convenient, and it can also be remotely transmitted. The pressure sensor is composed of a pressure-sensitive element and a conversion circuit, which uses the pressure of the measured medium to act on the pressure-sensitive element to produce a small change in current or voltage output.
The sensor 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, so that industrial automation equipment and engineering operation control are more intelligent.
In terms of price, pressure sensors are naturally more expensive than pressure switches, because pressure sensors have internal signal conditioning circuits. However, considering the service life and safety, the cost performance of pressure sensors is much higher than pressure switches. The after-sales service and product reputation of pressure sensors , The market difference is better than the pressure switch, obviously the pressure sensor should be preferred.