When the signal wires of the field instruments are removed, will the DCS screen display the maximum value or the minimum value?
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The company uses the Emerson DeltaV system; there is a safety barrier between the cards and the field instruments (the instruments are powered by the safety barrier). If the signal wires of the field instruments are removed, can the minimum value be displayed on the DCS screen? How to achieve it? Automatic control instruments
For the RTD temperature safety barrier, it is possible to set maximum and minimum fault outputs; generally, for instruments, this value corresponds to -24% of the display range. Is it possible to modify this value in the configuration settings? It seems that the channel settings cannot be altered
Most systems come equipped with corresponding fault detection functions, and different systems provide different types of alerts; for example, in Hilscher’s system detection data, the presence of the letters “U”, “E”, and “S” usually indicates a fault in the instrument or the wiring
This is determined by your settings and the system’s rules
DelteV’s AI module has circuit detection; a disconnected wire will trigger an open circuit alarm
In the case of a general signal disconnection with Emerson’s system, either the maximum or minimum value will be displayed. I’m not sure under what conditions the minimum value is shown and when the maximum value appears, but at the same time, an alarm for the disconnection will be triggered. But if you want to achieve the goal of displaying the minimum value, you can just use a simulated value, or set it manually at the engineer station – why go through the process of breaking the connection?
In the case of a general signal disconnection with Emerson’s system, either the maximum or minimum value will be displayed. I’m not sure under what conditions the minimum value is shown and when the maximum value appears, but at the same time, an alarm for the disconnection will be triggered. But if you want to achieve the goal of displaying the minimum value, you can just use a simulated value, or set it manually at the engineer station – why go through the process of breaking the connection?
It is to prevent an interlock alarm from being triggered after a wire break. For four-wire instruments such as electromagnetic and mass flow meters, they are connected directly to the AI card through an AI safety barrier; when power is lost, negative values appear on the DCS display ； 2-wire instrument, powered by a safety barrier; displays the maximum value in the event of a power loss. What I mean is, can a two-wire instrument show a negative value on the DCS screen after power loss, just like a four-wire instrument does?
During the configuration of the DCS system software, settings can be adjusted as needed.