Pressure Transmitter Working Principle The pressure on the pressure transmitter acts as a force on the diaphragm – depending on the applied pressure the diaphragm either expands or compresses, and the resistance value changes accordingly. The value is then transmitted as an electrical signal.

Differential Pressure (DP) transmitters measure the difference between two pressures. They use a reference point called the low-side pressure and compare it to the high-side pressure. A DP transmitter can be used as a gauge pressure transmitter if the low-side is left open to the atmosphere.

Differential Pressure (DP) Level Measurement uses pressure readings and specific gravity to output level. DP Level is a common measurement technique that is used in a wide variety of applications.

DP Transmitter installed at the exact HP tapping point

1. At Zero level = 0 mmwc.
2. At Span level = H x Specific gravity. = 500 x 1.0.
3. Then Range = 500 – 0 = 500 mmwc.
4. At zero level (LRV) = H1 x specific gravity.
5. At 100% level (URV) = (H1 + H2) x specific gravity.
6. Range = URV – LRV = 600 – 100 = 500 mmwc.

Differential pressure transmitters (also called DP transmitters) are among the most versatile measuring instruments. In addition to pressure, they are used to measure level and flow in many industries, on a wide variety of fluids even at high temperatures.

The working principle of pressure gauges is based on Hooke’s law, which states that the force required to expand or compress a spring scales in a linear manner with regards to the distance of extension or compression. There is inner pressure and outer pressure.

DP transmitter level measurement calculation. We base differential pressure level measurement in open tanks on the Pascal equation for hydrostatic pressure. Therefore pressure (P) equals the liquid’s density (ρ) times acceleration due to gravity (g) times the liquid column’s height (h), or P = ρ * g * h.

When a D.P. Transmitter is used for the purpose of measuring a level, it will be called a level transmitter. The pressure at the base of a vessel containing liquid is directly proportional to the height of the liquid in the vessel. This is termed hydrostatic pressure.

A differential pressure transmitter is an instrument that can consistently and accurately create a pressure drop in a pipe and then use the pressure measurement on either side to provide the rate of flow within the pipe. A differential pressure flow transmitter can be easily installed in many applications.

Also known as pressure level transmitters, these transmitters help in determining fluid contents of a container by measuring the pressure of resting body of the fluid within it. The greater the force of liquid, the greater the volume of fluid.

Well then that dp transmitter at zero trim, so its zero measurement has real pressure of minus 100inH2O. and when trimmed zero in these circumstances, the transmitter will send a signal to 0% (4mA for example). Calculation details can be developed with reference to the previous post.