What is a signal relay? Features, applications and differences from power relays？

1. What is a signal relay
A signal relay is a kind of relay, which is a recording element in a relay protection device and an electrical automatic device, which can give an obvious signal for the state of some devices or devices. The signal relay has a signal plate or light signal for local display and manual recovery, and can also output a contact signal and an electrical pulse signal for manual recovery to start the central sound circuit of the power plant and substation, and provide action information to the event sequence recorder.

2. Main characteristics of signal relay
The signal relay features gold-plated contacts and a forked cross bar construction to provide excellent contact reliability even under small signal loads. Since signal relays are mainly used to switch current, they are mainly C-contact structures, they are compatible with reflux installation, and reel packages can also be installed multiple times.

3. Application of signal relay
Signal relays are widely used in industry and People's Daily life: signal relays can be used in security devices, gas detectors and other disaster prevention equipment, alarms and other anti-crime equipment; Signal relays can be used in test and measurement devices, oscilloscopes and measuring equipment, IC testers and other inspection equipment, input/output switching, power switching; In terms of industrial equipment, it can be used for machine tools, forming machines, welding machines, placement machines and other industrial robots; Signal relays can also be used for amusement equipment.

The difference between signal relays and power relays, automotive steering signal relays and reed relays
(1) Signal relay and power relay
Signal relays and power relays are very similar in construction, the main differences being size and rated voltage and current. Power relays are rated for 250VAC or 30VDC and current from 2A above. They range in size from small PCB mounting fiber packages to large panel mounting screw terminal modules. The rated voltage of the signal relay is between 5VDC and 30VDC; Ac specifications are sometimes given, but only 125VAC. Rated current 2A or lower. Signal relays come in relatively small PCB mounting brick packages, which can be SMD through-holes, but some versions also come in panel or DIN rail packages.
Other nuances include: Switching time: Signal relays can also provide slightly faster switching (~3ms) than power relays due to their smaller size.
Switching form: The most common contact form for signal relays is DPDT, compared to SPST for power relays.
Insertion loss: Signal relays can be used to switch radio frequency (RF) signals and have insertion loss specifications.
(2) Signal relay and automobile steering signal relay
A signal relay and a car turn signal relay are two different things. Signal relays are the ones we've been talking about in this article and are used to switch low-level electrical signals. The turn signal relay is a power relay used to switch power to the turn signal light in the car. These relays typically have current ratings higher than 5 amps and are much larger than signal relays.
(3) Signal relay and reed relay
A reed relay is a small signal relay with a special structure similar to a reed switch. These relays have magnetic contacts on which the coil acts directly, do not require an armature, and are usually sealed in a glass tube.
Compared to traditional armature-based signal relays, reed relays are faster (1ms switching), more durable, have a smaller capacitance (~1pF). But the shortcoming of reed relays are obvious: susceptible to external magnetic field interference, may produce misoperation. Sensitive to temperature changes, too high or too low temperature will affect the performance of the relay. Limited scope of application, usually used for low-power, low-voltage switching applications.