Experts, please discuss the types of signals transmitted between electrical instruments in large-scale units and the specific hardware implementation methods
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As far as I know, in instrument control systems related to electrical equipment, the instruments generally send a dry contact signal to the electrical system through relays, which serves as a start signal for the electrical motors. In turn, the electrical system sends a dry contact signal back to the instruments as a feedback signal indicating its operation status. The instruments also provide start and stop signals to the electrical system; some of these signals are in pulse form. Any expert who understands this process could please explain how it works in detail, that is, the entire mechanism of this circuit. Since I’m just starting out with on-site instrument maintenance, I’m not quite clear on how the circuits involving relays work in detail. For example, is the pulse signal generated by software triggers or some other mechanism?
I’ve never heard of pulse signals existing. . Waiting for the expert to give an explanation
To control an electrical appliance using a gauge, it is first necessary to determine the control parameter for that gauge. The gauge must monitor this parameter; once the detection signal reaches the gauge, it is compared with the preset control parameter within the gauge, and then a signal is generated to control the electrical appliance and regulate the liquid level. When the detected liquid level is below the desired level, the motor is started, while it is turned off otherwise. Instrument output signals include switch signals, analog signals, as well as AC and DC current and voltage signals. When controlling electrical devices, a conversion unit such as a relay is usually used; however, there are also cases where the devices are driven directly, depending on the specific requirements. That’s roughly how the principle works.............
I understand the general principle, but I’m wondering if there’s a more detailed explanation
To be honest, it’s good that you want to learn *; the key is to learn it on your own. Forum discussions can only address one topic at a time, or they will provide you with just a preliminary overview. Regarding your question, it is recommended that you take a look at the schematic diagram of the secondary circuit for electrical control. You will know about the signals related to electrical operations, such as start, stop, and permission to start. The instrument sends signals to the electrical system; these signals can be in the form of continuous contacts or pulses. A pulse signal is actually a square wave, meaning that the duration of the signal being on or off is 1 second, 2 seconds, etc. Implemented through software.
The standard motor start signal is a pulse signal; you’ll understand this if you look at the motor control circuit. Just press the start button once, rather than holding it down. For reliability, the instrument can provide several more signals for closed, open states as well as open states; these are the pulse signals.