Can thermal resistor and thermocouple modules achieve redundancy?
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Can thermal resistor and thermocouple modules achieve redundancy? It seems that nowadays it’s all about CPU, communication, and redundancy in DIDO AIAO.
In the systems I have used so far, I have not seen redundancy achieved using thermal resistor and thermocouple modules. Both thermal resistor and thermocouple modules are used to measure some less important control points. All important temperature points need to be heated and converted into 4-20ma signals, after which redundancy can be achieved using an AI card
Thermocouples and thermal resistors don’t provide much redundancy in terms of card failures, as the probability of sensor damage is much higher than that of card failures. It is the multiple sensors that work together to ensure reliable temperature measurement.
The thermal resistor cards of the 300XP system in the central control unit can be used in a redundant configuration; the thermocouple cards (XP314) can also be used in this way
Whether redundancy is needed depends on its measurement principle. I’m not sure what the circuit principle behind temperature signal processing is, but I’ve never heard of any other DCS manufacturers having this feature
It’s not clear whose system it is; no conclusion has been reached.
Thermocouples can be used in a redundant configuration; this is applied in the coking units at our plant to measure the temperature inside the furnace. Two thermocouples are used, meaning that two thermocouples are placed at the same measurement point on-site. Two pairs of compensation wires (4 wires in total) are connected to the terminal block in the control room, and from there they are connected to the channels of two redundant cards. A selection switch has been configured in the database, allowing the operator to choose whether to use thermocouple No. 1 or No. 2 for the cascade control of the furnace. Under normal conditions, the temperatures of both thermocouples are displayed on the operation panel; one is used for control purposes, while the other is used for monitoring as a reference. If the thermocouple in use encounters a problem, the operator can switch to another one.
Redundancy is possible, haven’t you used it before?
Yokogawa's DCS enables card redundancy for RTDs and T/Cs