May I ask about the squaring issue of differential pressure transmitters?

Differential pressure transmitters are commonly used to measure flow rate, with their output signal being proportional to the square root of the measured flow rate. Therefore, to obtain the true flow rate value, it is necessary to take the square root of the transmitter’s output signal. In DCS (Distributed Control System) systems, there are generally two methods for processing the signals from differential pressure transmitters: 1. Using a transmitter with a square-root function; in this case, the transmitter itself performs the square-root operation on the output signal, and the DCS receives this already-processed signal, which is then converted into a flow value based on the specified range. 2. Using the DCS system for square root calculation: In this case, the differential pressure transmitter outputs a signal that is proportional to the square of the pressure difference; the DCS system must first apply a square root operation to the received signal before performing range conversion. Regarding your specific question, if it involves taking the square root using DCS, the procedure is to first take the square root of the percentage signal returned by the table header in order to restore it to the actual flow signal. This percentage signal is usually based on the range of the differential pressure transmitter; it indicates what percentage the current differential pressure value represents of the transmitter’s full range. Assuming the signal received by the DCS is 4-20 mA, corresponding to a 0-100% range for the differential pressure transmitter: 1. Convert the 4-20 mA signal into a percentage signal ranging from 0-100%. 2. Apply a square root operation to this percentage signal in order to restore the actual flow ratio, since the flow is proportional to the square root of the pressure difference. 3. Convert the percentage signal after taking the square root into a flow rate unit, which usually requires multiplying by the maximum flow rate value. Therefore, if the transmitter’s range is flow rates from 0 to X units, then the formula for calculating the flow rate might be: Here, the signal percentage refers to the value after taking the square root, rather than the percentage corresponding to the original 4-20 mA signal. Therefore, the application of the range is carried out after taking the square root. The final flow unit depends on the transmitter’s calibration and range setting. .

For the process of taking the square root of a DCS value, range conversion must be performed first, followed by the square root operation. After taking the square root, there is no need to multiply by the root mean square of the range. Range conversion is used to transform the input signal into an appropriate operating range, while the square root operation is intended to eliminate the non-linear characteristics of the signal, making it more usable. The signal after taking the square root is usually expressed as a percentage, so there is no need to multiply it by the root mean square of the range.

Okay, thank you. I understand that the signal returned by the header is not a differential pressure signal; it should be the product of the differential pressure and other parameters, with that parameter being placed inside the square root. I’m not sure if that’s correct?