A signal relay is an electronic switching device that can receive an external input signal and control the switching operation of other devices based on the state of the signal.
In simple terms, the signal relay drives the circuit switch by "sensing" a small electrical signal, so that there is no direct connection between the control signal and the controlled device or circuit, but through the intermediary device of the relay to achieve control.
Signal relays play an indispensable role in modern industrial automation and control systems because of their fast response and high reliability.
In the power system, they are the key components of the protection equipment, used to achieve overcurrent protection, trip protection, etc., to ensure the stable operation of the power grid.
In the field of industrial automation, signal relays achieve precise control of equipment such as robotic arms and conveyor belts by expanding input and output interfaces, improving the efficiency and flexibility of production lines.
In the communication system, they are responsible for the switching and routing of signals to ensure the continuity and reliability of data transmission.
In the field of transportation, signal relays control traffic lights and railway crossings to ensure smooth traffic and pedestrian safety.
In medical devices, they are used to monitor patients' vital signs, control the operation of medical instruments, and improve the quality and safety of medical services.
In addition, in household appliances, signal relays also play an important role, such as in smart thermostats, timing switches and other equipment, they provide convenient automation control.
These application examples fully demonstrate the versatility and importance of signal relays in different industries, and they are one of the cornerstones of modern technological progress.
Measuring coil resistance: can be used to measure the resistance of the relay coil R×10Ω, so as to determine whether there is an open circuit phenomenon in the coil. The resistance value of the relay coil has a very close relationship with its working voltage and working current, and its working voltage and working current can be calculated through the resistance value of the coil.
Measure the contact resistance: with the resistance of the multimeter, measure the normally closed contact and moving point resistance, the resistance value should be 0; The resistance of the normally open contact and the moving point is infinite. So you can tell that one is a normally closed contact and that one is a normally open contact.
Measure the suction voltage and suction current: To test the relay, connect an adjustable power supply and ammeter. Gradually increase the voltage until the relay closes, recording the voltage and current. Repeat for accuracy. To measure release voltage and current, decrease the voltage until the relay opens, noting the values. The release voltage should be 10-50% of the pull voltage; if it's below 10%, the relay may not operate reliably, risking circuit stability.
The classification of signal relays can be divided according to different criteria such as their working principle, working current and operating speed.
First of all, according to the principle of action, signal relays can be divided into electromagnetic relays, induction relays and thermal relays. Electromagnetic relays rely on the suction force generated by the electromagnet to drive the armature action, induction relays use the interaction of the magnetic field and eddy current, and thermal relays operate based on the characteristics of the bimetal sheet when heated.
Secondly, according to the different working current, signal relays can be divided into DC relays and AC relays. Dc relays are suitable for direct current circuits, while AC relays are suitable for AC circuits. In addition, there are both AC and DC relays, which can operate in both types of circuits.
Finally, according to the speed of action, the signal relay can be divided into quick relay, normal action relay and slow relay. The armature action time of the quick-acting relay is less than 0.1 seconds, the action time of the normal acting relay is between 0.1 and 0.3 seconds, and the action time of the slow acting relay is more than 0.3 seconds.
These classification methods help engineers and technicians choose the right signal relay according to the specific application needs to ensure the efficient and stable operation of the system.
Note on signal relay selection
When selecting a signal relay, the following key factors need to be considered to ensure its suitability and reliability.
First, determine the type of relay according to the specific needs of the application, such as solid-state relays for high frequency operation, and electromagnetic relays for high current control.
Second, check the electrical parameters of the relay to ensure that its rated voltage and current match the application environment to prevent overload and damage. At the same time, the contact capacity of the relay is evaluated to ensure that they can withstand the expected load. In addition, the environmental tolerance of the relay is considered, including its performance under extreme temperatures, vibrations and shocks.
The installation method is also an important factor, and the selection of relays suitable for the system installation requirements can simplify the integration process. Electromagnetic compatibility can also not be ignored to ensure that the relay does not interfere with other devices in the system.
Finally, consider the size and weight of the relays to ensure that they fit in the mounting space and do not impose an additional burden on the system. Combining these factors, the signal relay suitable for a specific application can be accurately selected, thereby improving the stability and efficiency of the entire system.
