Discussion on the DO signal from instruments to electrical systems?
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If the DCS of the instrument generates two DO signals for the electrical system, one for starting and one for stopping, are these signals pulse signals? If the instrument DCS generates a DO signal to be sent to the electrical system in order to start or stop the motor, is such a signal a self-sustaining signal? Which of these two approaches is better? If modifications are needed, is it always easy to do so for instrument DCS? Is it also easy to modify in the system?
Why not keep the signal on? DO turns off when it is turned off. . A relay can be selected. .
Why not keep the signal on? DO turns off when it is turned off. . A relay can be selected. . Maintain long \"1\" signal
Actually, both can be implemented in DCS. The first two DO signals are suitable for use in interlock modifications within signal control; they allow continuous current signals to be converted into pulse signals, thereby improving resistance to interference. They are also useful for setting fixed values. As for the latter DO signal, it simply represents whether a relay is powered on or not. Do you want to know more details? I’m not sure if this answer meets what you were asking for
Hehe, I didn’t expect the post to be recommended by the moderator
Our factory uses Hilscher systems; for the electrical control of high-voltage frequency converters, there are also two DO signals. A time relay is used to keep the signal at \"1\" for 5 seconds. It seems that some kind of interlock mechanism is involved in this process. However, the frequency conversion control cabinets produced by CRRC can maintain that state on their own
In my opinion, whether the start/stop command sent to the electrical system by the instrument control system is a long signal or a pulse signal depends on the design of the electrical cabinets; in either case, it can be implemented in an instrument control system
Both can be achieved very well. A DO works by reversing the state of a relay to enable start/stop; usually, it is necessary to keep the relay in that state, which requires a continuous current signal. The two DOs represent on and off respectively; usually this results in a long pulse signal, which may also have a slight delay.
This post was last edited by Albertlu on 2011-7-9 at 20:18. It is possible to have 1 DO output; I’ve seen some DOs defined with a default state, but in reality there are two states. Regarding self-holding signals, the signal state can be locked in place using electrical circuits. A DO is a digital pulse signal, and its state can be maintained through a holding circuit – it simply becomes a circuit state. In important safety scenarios, a self-locking circuit is required, and it must be activated manually.
Regarding self-protection signals in DCS systems, it is possible to achieve self-protection using logic, as well as through electrical contacts; using both types of self-protection together may seem like a good idea, but it is actually unnecessary. Yet, factories tend to do this quite often. . . . Hehe
Make a do switch into a normally closed configuration and insert it into the circuit that controls the motor (using a relay for isolation). Start or stop. . Pulse signals are used in all cases. The simplest way to implement it.