There’s a problem with the Yokogawa DCS3000; please help to take a look.
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There is a liquid level sensor at LT1001; after PVI processing, its identifier becomes LIT1001. A logic circuit uses the value LIT1001.ALRM.HH, with a threshold of 80%. Currently, the liquid level is within normal limits. If I want LIT1001.ALRM.HH to take the value 1, thereby triggering a high-level alarm for LIT1001, can I set LIT1001 to a calibration value of 90% in order to make LIT1001.ALRM.HH equal to 1? I tried it, but it seems it doesn’t work; I was doing a simulation test.
Verification isn’t possible; click on PV, select ITEM in the pop-up dialog box, enter RAW, and then type 80. That’s it.
With the CAl verification method, no alarm is triggered for PV; by clicking on PV on the panel and going to item raw, it is possible to modify the PV value
Thank you all for your advice. So what is the purpose of adding a parity bit to the PV value? Also, when I’m performing simulation tests, why can the DI and DO points be directly set to ON/OFF?
For the PV and MV of the switch instrument block, there are three options: 0, 1, and 2. What do they represent respectively? How is it calculated?
MV is your output, while the value that is fed back is PV. Since most valves have two types of feedback, there are several possible combinations. By default, when the open feedback is set to ON and the closed feedback is set to OFF, the actual PV value is 2; if the open feedback is set to OFF and the closed feedback is set to ON, the actual PV value is 0. If both are set to OFF, the actual PV value is 1. If both are set to ON, a PERR alarm is triggered.
Bro, thanks for your guidance. What I don’t quite understand is that in normal systems, when the on/off feedback is set to ON, the value of the corresponding DI point changes from 0 to 1; so how does a value of 2 appear?
That is a characteristic of switch-type instruments; this applies to both SI and SO instruments.