Discussion on AI input for two-wire and four-wire systems
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The specific wiring diagram is shown below. The loop consists of a transmitter, a safety barrier, and an AI card; the AI card uses a two-wire connection for power supply. The 24V DC+ terminal of the isolated safety barrier is connected to the 24V DC- terminal that supplies power to the DCS AI card, while the 24V DC- terminal of the same safety barrier is connected to the 24V DC+ terminal of the DCS AI card. The 24V DC- terminal of the DCS is grounded. Since the safety barrier is located on-site, there is an additional power supply; in this case, the 24V DC- terminal remains unconnected. The system functions normally under these conditions. However, sometimes the DCS reports a loop fault, with the displayed value indicating that it is outside the specified range. During a fault, the voltage at the output terminals of the safety barrier on-site is 14.4V, whereas under normal operation the voltage at the same location is 17.7V. The load on the transmitter remains relatively stable, staying around 13.6 mA. Discussion: 1) Why does this wiring method allow the system to function properly?； 2) Does this connection method have a significant impact on the DCS system?
Let me tell you something; that guy talking about football is being really annoying and chaotic,..............
The APP has removed the line breaks and spaces, why?
When connected to a 24V power supply, it can function properly. The DCS is not working properly, didn’t you say that?
What are you talking about? I can’t understand it; there’s a wiring diagram on the safety barrier. The safety barrier has its own independent power supply; simply connect its output to the non-power supply terminal of the AI card.
There are several meters, and only one of them occasionally fluctuates to its maximum value, indicating a short circuit; the readings of the other meters are normal.
Yes, as is usual, I should inform you about the previous issues that remain unresolved; things don’t seem to be in order, and normal instructions shouldn’t be given, but at present instructions are being issued. Let’s take them out and discuss them together.
If the DCS module has an output voltage and the safety barrier also has an output voltage, the positive and negative poles must be connected in reverse; otherwise, no circuit will be formed and the signal from the safety barrier cannot be detected
Is the safety barrier installed on-site? Is power supplied on-site? How many safety barriers are required for continuous power supply service? This problem is likely caused by insufficient voltage at the safety gate. It is recommended that one power supply circuit be used for no more than 3 safety gates; it’s best to have one power supply per gate. The longer a safety gate is in use, the stricter the requirements regarding its power supply conditions. For normal operation, it is advisable that the voltage be no less than 22V. Additionally, the distance between the 24V power source and the safety gate should not be too great. The safety gate’s manual should contain the required usage specifications and installation guidelines; it is recommended that you take a look at those
The card module does not receive power; the safety barrier provides the power