The relationship between the differential pressure value and flow rate of differential pressure transmitters
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I asked: As long as there is a differential pressure value (for example, 0.01%), will there necessarily be a display of the flow rate? Another issue is that with orifice plate flowmeters, there is a range within which the measurements are the most accurate. If the actual flow rate is below 10% of that range, then are the measurements no longer accurate? Thank you!
According to the measurement principle of differential pressure flow meters, flow rate is present as long as there is a differential pressure; however, to ensure measurement accuracy, differential pressure flow meters are usually operated at more than 1/3 of their full scale. Also, to overcome measurement interference, small-signal rejection is usually implemented. That is, below the small-signal (differential pressure) level, the instrument output is 4mA
Simply put, there is a square-root relationship between differential pressure and flow rate: a differential pressure of 0.01% corresponds to 0.1% after taking the square root. The actual differential pressure is very small, but the flow rate becomes relatively large after applying the square root function. To avoid this situation and ensure accurate measurements, it is necessary to implement a low-flow cutoff mechanism – that is, the flow rate should be set to 0 when the differential pressure falls below a certain value; for example, the flow rate should be 0 when the differential pressure is less than 1%. The accuracy is poor when the flow rate is below 10%; typical differential pressure flow meters require a flow rate of over 20% in order to maintain good accuracy