Loop-powered DP transmitter

Hi guys! How does an applied pressure to the “High” pressure port on the transmitter affect the electrical signal? Could someone share any kind of information about that or please reveal the question. Thanks!

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The most common sensing element used by modern DP transmitters is the diaphragm. One side of this diaphragm receives process fluid pressure from the port labelled H while the other receives process fluid pressure from the port labelled L. Any difference of pressure between the two ports causes the diaphragm to flex from its normal resting position. This flexing is then translated into an output signal (4-20mA) by either a strain gauge, differential capacitance or a vibrating wire depending on the manufacturer and model of the transmitter.

If the pressure applied at the port H is greater than that at the port L of the DP transmitter, the output signal from the transmitter will increase and tend towards the 20mA mark. If on the other hand the pressure at the port L is greater than that at the port H, the output signal from the transmitter will decrease and tend towards the 4mA mark.

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