Switch concept
The switch quantity is the on-off signal, passive signal, the resistance test method is resistance 0 or infinity; mainly refers to the binary input and output, and refers to the auxiliary contact of a device, such as the temperature controller of the motor Auxiliary contacts of the relay (displacement after the motor is over-temperature), auxiliary contacts of the valve cam switch (displacement after the valve is switched), auxiliary contacts of the contactor (displacement after the contactor is activated), thermal relay (The thermal relay changes its position after the action). These points are generally transmitted to the PLC. The power supply is generally provided by the PLC or comprehensive protection device. It does not have a power supply itself, so it is called a passive switch contact, also called a PLC switch.
It can also be an active signal. The professional name is a step signal, which is 0 or 1, which can be understood as a pulse quantity. Multiple switching quantities can form a digital quantity.
The origin of the switch
During World War II, in order to ensure the stable operation of electrical equipment, engineers needed to compile a set of general electrical equipment standards to unify the standards of electrical equipment switches and rotary switches in various fields such as navy, army, air force, civil defense, and logistics.
In particular, the signs of the switches must be trained in just a few minutes so that soldiers and maintenance workers from different countries can recognize and use them correctly. Some engineers thought of a simple solution. That is the internationally accepted binary code
In binary:
"1" means "on"
"0" means "off"
So, there are "|" and "O" on the switch
Later the International Electrical Engineering Committee (IEC)
Formally proposed in the technical specifications prepared in 1973
Put "|" and "O"
What is a switch
As a mark of power switch cycle
my country's national standard GB 15092 is also clear
The circle "O" represents the circuit is disconnected (that is, "turn off the light")
The straight bar "|" represents the circuit is closed (that is, "turn on the light")
Switch application
The figure above is a typical device that can output switching signals. When the pressure is high, the C and B contacts are closed and connected to output a high pressure signal. When the pressure is low, the C and A contacts are closed and connected to output a low pressure signal.
With such a signal, the local pressure signal can be transmitted to the remote electrical control cabinet to participate in automatic remote control, where C and B are a switch value, and C and A are also a switch value. So a switch contact is a switch, and its characteristic is that it is either on or off at the same time. On is 1, it means there is a signal, and off is 0, which means there is no signal. This is the so-called switch signal.
Although the pressure gauge can transmit the pressure signal to a remote place, it only transmits the signal whether there is pressure, and it is impossible to know the real-time pressure value.
The device in the figure above is called a pressure transmitter. The inside of the pressure transmitter is a circuit board, and a pressure sensor F is connected to the circuit board.
Its working principle is that the pressure sensor F transmits the detected pressure to C of the circuit board. After the detection signal enters the circuit board, the pressure signal is converted into a current signal by the conversion and calculation of the circuit board. Points output. The right side of the figure is a schematic diagram of the conversion process. It can convert a 0-10kpa pressure signal into a 4-20mA current signal, which is output by the two points A and B. At this time, we say that the two points A and B output an analog signal. The characteristic of an analog signal is that its value is continuously variable within a numerical range.
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Name: Network IO Controller
Network: 4G Full Netcom
Introduction: ZHC4922 is an industrial-grade 4G RTU, providing 4 DI, 4 DO, 4 AI and 1 RS485 interfaces, supporting local logic processing operations, automatic acquisition and active reporting , MQTT RTU/TCP adaptive, automatic calibration threshold reporting, configuration software docking, dry and wet node IO detection and other features. The above-mentioned one is the IO controller in the Internet of Things, which can also be called the switch control module