The differential pressure flow transmitter shows full scale at the field, but the DCS does not indicate full scale
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This is a strange issue. The field instrument is a differential pressure flow transmitter with a range of 0–6 KPa, while the data sheet specifies a range of 0–5000 Nm3/h. However, the DCS shows a range of 0–8000 Nm3/h. The DCS uses Honeywell’s PKS system and a C300 controller. When the field instrument reaches its full scale, it sends a 20mA signal to the DCS; regardless of whether the flow rate displayed on the DCS screen is 8000 or 10000 Nm3/h, it should show the full scale value. But in reality, the DCS displays 5000 Nm3/h. My assumption is that the DCS configuration involves more than just a display block – the 20mA signal from the AI input is processed through some auxiliary block or other mechanism, and after calculation, the value of 5000 Nm3/h is obtained. Therefore, no matter what the maximum value shown on the DCS screen is, it always displays 5000 Nm3/h. I’m not sure if my reasoning is correct; please advise me
It’s a orifice plate flow meter, right? The maximum flow rate specified in the orifice plate design specifications is 5000; therefore, the upper range limit in the DCS should be set at 5000, not 8000. The value of 8000 you mentioned is likely the value before the parameters were set correctly – once the parameters are properly set, it should be 5000......
I used to work with the CS3000. If the range is specified directly in the PVI block (without any further processing), then when 20mA flows in, the DCS display should show the full range for PKS. I’m not sure where the range should be entered
It’s a orifice plate. I know it should be 5000; what I’m asking is why, when 20mA enters the DCS, it doesn’t show the full scale value (regardless of whether the DCS’s scale is correct or not, it should show the full value since the DCS has received 20mA)
“But the result is that the DCS shows 5000 Nm3/h – isn’t 5000 the full scale value?.....
On the DCS display, the range is 0–8000; when the value reaches 5000, it already corresponds to a 20mA signal
What value do you get when using a standard signal source to supply 18 or 19 mA? If the value is less than 5000, it indicates that the range set by the DCS is correct; the value of 8000 shown on the screen is incorrect. If there is no change in this value, then there is a problem with the DCS – it could be a hardware issue or a software issue.....
It must be a problem with the DCS; it could be related to some aspect of its operation. My 4-20mA signal corresponds to a value of 0-5000. There are no issues at the field level; the problem lies in the fact that 20mA results in a value of 8000 displayed on the DCS screen
First, determine whether your DACA block is linear or square-root; then determine the range. Then you need to go to the lower-level configuration to check if a compensation block is being used EQA/EQB is used. . . . Plug that formula in to do the calculation.
What is the EQA/EQB block? Could you explain it briefly? Thank you
I’ll go ask the DCS staff in a bit and get back to you then