Regarding AI and AO of two-wire intelligent positioners
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A two-wire intelligent locator receives the AO signal from the DCS, along with an AI signal indicating the valve position. My problem lies in the feedback signal; for DCS configuration this involves two points, but the positioners use a two-wire system. So how are these two signals transmitted through just one point? Also, I heard that smart locators that support HART can transmit 0 and 1 signals in addition; so what should I do to send analog signal responses? Can’t intelligent locators that are not HART send back responses either? PS: A two-wire intelligent locator.
I don’t understand what the original poster means. . The locator you’re talking about is just a locator – it’s a 2-wire system; one wire is connected to it, and this locator comes equipped with a valve position transmitter. . So there is another wire; in simple terms, you can think of it this way: the locator consists of two parts, the locator itself and the transmitter. The locator receives the AO signals from the DCS and sends an AI signal back to the DCS. It’s not the case that the locator has only two connections – one wire – with no other place for another wire to connect to.
Based on the owner’s description, it seems that the signal indicating the valve position is transmitted to the DCS system via a bus. To receive this signal, the AI card in your DCS system must support the bus protocol used by the locator; in addition, the system needs software capable of managing bus devices, such as Emerson’s AMS. Siemens’ PDM and so on.
This locator definitely has terminals that support analog (valve position feedback) output functionality. Take a look at the manual; a cable needs to be added to connect to the AI.