Regarding double-flange differential pressure transmitters
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Under normal circumstances, when installing a differential pressure transmitter, the high-pressure side is assigned to the lower pressure tap, while the low-pressure side is assigned to the upper pressure tap; this is known as negative migration； So, the low-pressure side is equipped with a pressure tap at the bottom, while the high-pressure side has a pressure tap at the top; measurement is still possible in this case. Then why is this approach rarely used?
According to your “reverse connection” plan: 1. At zero liquid level, the transmitter outputs at full scale. 2. Then the liquid level rises, and the transmitter output gradually decreases. . . Up to an output of 4 mA.
In my opinion, this is just a *habit. Under normal circumstances, the pressure at the lower flange is high while the pressure above it is low; therefore, the lower flange is connected to the side with positive pressure
I disagree with the second point; as the liquid level rises, the 4-20mA signal will certainly change gradually. If the upper and lower flanges are installed in reverse, it can still be used as long as the parameters are set correctly
As the liquid level rises, does the differential pressure decrease? Correspondingly, how does the current change?
The lower limit set in the parameter settings is 4mA, while the upper limit is 20mA. If the lower limit is set to 20Kpa and the upper limit to 0KPa, then the current value will also increase
In yours, there are two wires—one red and one blue. The red one connects to the positive terminal, and the blue one to the negative terminal. If I reverse it, I’ll scold him; it’s not that it can’t be used, but then how can others maintain it?
Wouldn’t it be even more troublesome to write a program specifically for that configuration? In many programming tasks involving analog signal processing, it’s sufficient to simply call a function block.
Isn’t this similar to using positive and negative logic (0, 1), which feels a bit awkward? Walking forward is walking; walking backward is also walking. Then why not walk backward? Generally speaking, it’s about the way of thinking. Management exists to make things easier and more efficient; if it’s necessary to go through unnecessary steps, then so be it:$