Number of circuits for the safety barrier
Thread Content
The image above shows the specifications for the safety barrier as well as a physical diagram of it. From the wiring, it seems that multiple circuits feed into the safety barrier, while there are only two wires connecting the safety barrier to the data forwarding card or the main control card. It’s strange that, aside from the safety barrier on the bus instrument, a safety barrier within the DCS system can handle multiple circuits, whether they are input or output circuits.
This is a P+F two-input two-output safety barrier. One analog input signal enters the safety barrier, while two analog signals are output to the DCS or SIS. The values of the two outputs are the same.
First of all, thank you for your reply; I roughly understand what you mean. Is there a reverse scenario as well, where the computer sends 4-20mA signals to the safety barrier, and this safety barrier in turn outputs two or more signals to the field instruments? For example, one signal from the computer and one signal from the safety barrier, resulting in two signals going to the shut-off valve. I’m not sure whether the instrument design specifications allow such operation; I’ve never seen this practice used with instruments in the field, but I also don’t know if it’s permitted by the specifications. Technically speaking, it’s similar to the situation where a laptop’s USB port cannot power multiple USB hubs
1. The wiring in the diagram is of a two-outlet type. No problem. 2. Your idea is whether it can be used in reverse; personally, I think it can’t! The function of an isolated safety barrier is to limit voltage and current. If it is used in the reverse direction, although the signal is isolated, it may not be able to meet the voltage and current limitation requirements of a particular intrinsically safe circuit.
1. The diagram above shows a one-in-two-out configuration, which is fine. 2. Connecting it in the opposite direction as you think is, in my opinion, not a good idea. The function of an isolated safety barrier is to limit voltage and current; reverse connection may not meet the requirements of a particular intrinsically safe circuit.
1. The diagram above shows a one-in-two-out configuration, which is fine. 2. Connecting it in the opposite direction as you think is, in my opinion, not a good idea. The function of an isolated safety barrier is to limit voltage and current; reverse connection may not meet the requirements of a particular intrinsically safe circuit.
1. The diagram above shows a one-in-two-out configuration, which is fine. 2. Connecting it in the opposite direction as you think is, in my opinion, not a good idea. The function of an isolated safety barrier is to limit voltage and current; reverse connection may not meet the requirements of a particular intrinsically safe circuit.
1. The diagram above shows a one-in-two-out configuration, which is fine. 2. Connecting it in the opposite direction as you think is, in my opinion, not a good idea. The function of an isolated safety barrier is to limit voltage and current; reverse connection may not meet the requirements of a particular intrinsically safe circuit.
First, it should be clear that analog safety barriers can generally be divided into two types: 1. Analog input type (field transmitter signals are sent to the DCS or secondary instruments)； II. Analog output type (DCS or secondary meter outputs to the field control valve). These are two types of safety barriers that cannot be used together. At one point, you mentioned whether a card with 4`20ma can power 2 circuits on site. As far as I know, there is no such output-type safety barrier. From a control perspective, only proportional control and ratio control require one circuit to control two valves; however, the usual practice is to use two AO signals for each valve.
Is the CleanClear a signal distributor that sends signals in and out once? What kind of safety barrier is this, anyway? Does this device require an additional power supply? Otherwise, 4–20mA signals will be divided into two channels; where does the electrical energy for the other channel come from? All safety barriers I’ve seen have two wires for input and two wires for output, with one channel connected to another; could it be that my knowledge is limited? {:2_45:}