Generation and elimination of the error between the on-site cumulative value and the central control cumulative value
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There is a paddle flow meter on site that transmits current signals to the control room (the flow meter has a pulse output function, but the control room does not have pulse cards); the paddle flow meter’s display shows cumulative values, and the control room also has cumulative flow data. At the same time, the accumulation was reset, and it was found that the central control system indicated an accumulation of 560 M3, while the actual amount on site was only 543 cubic meters. Check that the ranges are the same, and the instantaneous flow rates are also the same. How does this cumulative error arise? How to eliminate it. My personal understanding is that the time basis for cumulative totals in the headers may be inconsistent. For example, the header counts once every 0.001 seconds, while the control unit does so every 0.0001 seconds. Or there is an error in the timing measurement; the value shown as 0.001s on the gauge head corresponds to 0.00099s in the control room. The most likely explanation is very small errors that occur during current transmission, but these errors become apparent over time as they are amplified. Is there any way to eliminate this cumulative error? Are there any other methods besides digital communication?
If your traffic is stable, then this represents a slight deviation in the current output (or what is received by your card). In such cases, use a high-precision multimeter (or signal generator) to calibrate both sides.
Hehe, this is a common issue – conversion errors. I advise the original poster to stop relying on the on-site accumulation values and to use the DCS readings instead; there’s no need to worry about the accumulation values shown on those on-site gauges.
This error arises during the signal conversion process. Apart from direct digital (pulse) communication, it cannot be eliminated. The signals displayed in the control room undergo two conversions, one digital-to-analog and one analog-to-digital; it is inevitable that errors will occur. Apart from identifying a watch to determine its time, there isn’t really a better way. For volumetric rotating machines like scrapers, the cumulative values may be in digital form from the point when the signal is generated until it is displayed, which makes them relatively more accurate. If possible, multiplying the signal by a coefficient before it is displayed in the control room can reduce the error between the readings at the two locations.
I have also noticed this phenomenon. I would like to ask whether, in such cases, the cumulative flow measurement provided by DCS is more accurate or the reading from the gauge on site is more accurate