Real-world issues with flowmeter measurement in DCS and secondary systems?
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Our company currently has a flow meter that measures cumulative flow, and its signal needs to be fed into the DCS. However, there is always a certain discrepancy between the values shown by these two devices. The management requires that the instantaneous flow values displayed by both devices be exactly the same, as well as the cumulative flow values. Could everyone help analyze what the problem might be, how it can be resolved, and what measures can be taken?
It’s necessary for them to be exactly the same instant by instant, but it’s impossible for them to remain consistent over time. It’s impossible for different systems to have the same cumulative methods!
You should also provide more details – deviations? How old?
First, it is necessary to check whether the instantaneous values are exactly the same; if they are not, it may be due to too large a distance, which causes the current signal to attenuate； Then figure out whether the accumulation methods of the secondary meter and the DCS are consistent ； Can the cumulative value of the secondary meter be read on the DCS display? ； It can be resolved through communication ；
The instantaneous flow rate must be displayed exactly the same way, and this can be achieved by precisely setting the range of the DCS 4-20MA signal! The cumulative value must remain the same; therefore, the pulse output from the secondary meter needs to be connected to the DCS. Each time the secondary meter advances by one digit, it emits a pulse, and the cumulative value in the DCS increases by one digit! If the secondary meter can communicate with the DCS, the DCS can read the data from the secondary meter
Based on the deviation value, determine the correction coefficient or correction range, and apply the correction.
The cumulative value of DCS is smaller than that of the secondary meter; we have encountered similar problems as well. It is best to use communication methods or pulse input for data acquisition, rather than 4-20mA input.