Understanding the Basics of Differential Pressure Flow Transmitters

Differential pressure flow transmitters are essential instruments used in various industries to measure the flow rate of liquids, gases, and steam. These devices work on the principle of measuring the pressure difference between two points in a flow system, known as the differential pressure. By accurately measuring this pressure difference, the flow transmitter can calculate the flow rate of the fluid passing through the system.

POP-8300 free chlorine online analyzer
System Model POP-8300 free chlorine online analyzer
Measurement configuration (HClO)free chlorine..
total free chlorine/(ClO2)/pH/Temperature
  Free chlorine (0.00-2.00)mg/L(ppm);   (0.00-20.00)mg/L(ppm)
Measurement pH 2.00-12.00
range Temperature (0.0-99.9)℃
  Free chlorine 0.01mg/L(ppm)
Resolution pH 0.01
  Temperature 0.1℃
  Free chlorine Indication error 10%
Accuracy pH 0.1pH
  Temperature ±0.5℃
Sensor life pH/free chlorine sensor 12months(The service life is closely related to the measurement medium and maintenance frequency)
Communication interface RS485 MODBUS RTU communication protocol
  Number of channels Double channels
(4-20)mA Technical feature Isolated, reversible, completely adjustable, instrument/transmitter dual mode
output Channel configuration Programmable point to Free chlorine, chlorine dioxide, Temperature, pH
  Loop resistance 400Ω(Max), DC 24V
  Transmission accuracy ±0.1mA
  Number of channels Double channels
  Contact mode The first and second for photoelectric switch
Control output Load capacity Load current 50mA(Max),AC/DC 30V
  Control point Programmable function(Free chlorine, chlorine dioxide, Temperature, pH, Timing)
  Load capacity Load current 50mA(Max),AC/DC 30V
  Control point Programmable function(Free chlorine, chlorine dioxide, Temperature, pH, Timing)
Power supply Connected to electric supply
  AC80-260V;50/60Hz,compatible with all international
  market power standards(110V;220V;260V;50/60Hz).
Working environment Temperature:(5-50)℃;relative humidity:≤85% RH(non condensation)  
Power Consumption <20W
Storage environment Temperature:(-20-70)℃;relative humidity:≤85%RH(non condensation)
Installation Wall mounted(with the preset back cover)
Cabinet weight ≤10kg
Cabinet dimension 570*mm*380mm*130mm(H×W×D)

One of the key components of a differential pressure flow transmitter is the primary element, which creates a pressure drop in the flow system. This pressure drop is essential for accurate flow measurement, as it allows the transmitter to calculate the flow rate based on the differential pressure. There are several types of primary elements used in differential pressure flow transmitters, including orifice plates, venturi tubes, and flow nozzles, each with its own advantages and limitations.

model pH/ORP-5500 series pH/ORP online transmitting controller
Measurement range pH 0.00~14.00
ORP -2000mV~2000mV
Temp. ( 0.0~50.0)℃  (temperature compensation component:NTC10K)
Resolution pH 0.01
ORP 1mV
Temp. 0.1℃
accuracy pH 0.1
ORP ±5mV(electronic unit)
Temp. ±0.5℃
Approximate input impedance 3×1011Ω
Buffer solution pH value: 10.00ï¼›9.18ï¼›7.00ï¼›6.86ï¼›4.01ï¼›4.00
Temp. compensation range (0~50)℃(with 25℃ as standard)Manual and automatic temperature compensation
(4~20)mA characteristics Isolated,fully adjustable,reverible,instrument/transmitter for selection
Loop resistance 500Ω(Max),DC 24V
accuracy ±0.1mA
Control contact Electrical contacts Double relay SPST-NO,return model
Loop capacity AC 220V/AC 110V 2A(Max)ï¼›DC 24V 2A(Max)
Power consumption <3W
Working environment temperature (0~50)℃
humidity ≤85%RH(none condensation)
Storage environment Temp.(-20-60) ℃;relative humidity:≤85%RH(none condensation
Outline dimension 96mm×96mm×105mm(H×W×D)
Hole dimension 91mm×91mm(H×W)
installation Panel mounted,fast installation

Orifice plates are one of the most commonly used primary elements in differential pressure flow transmitters. They consist of a thin plate with a hole in the center, which creates a pressure drop as the fluid passes through the orifice. This pressure drop is directly proportional to the flow rate of the fluid, allowing the transmitter to accurately measure the flow rate. Orifice plates are simple, cost-effective, and suitable for a wide range of flow applications.

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Venturi tubes are another type of primary element used in differential pressure flow transmitters. They consist of a converging section, a throat, and a diverging section, which create a pressure drop as the fluid passes through the tube. Venturi tubes are more efficient than orifice plates in terms of pressure recovery and are often used in applications where energy conservation is important. However, venturi tubes are more complex and expensive than orifice plates, making them less suitable for some applications.

Flow nozzles are similar to venturi tubes but have a shorter, more streamlined design. They create a pressure drop by accelerating the fluid through a nozzle, which allows for accurate flow measurement. Flow nozzles are often used in high-velocity flow applications where accuracy is critical. However, like venturi tubes, flow nozzles are more complex and expensive than orifice plates.

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In addition to the primary element, a differential pressure flow transmitter also consists of a differential pressure sensor, which measures the pressure difference between the two points in the flow system. This sensor converts the pressure difference into an electrical signal, which is then transmitted to a control system for further processing. The control system calculates the flow rate based on the differential pressure signal and displays the result on a digital readout or transmits it to a data acquisition system for recording and analysis.

Overall, understanding the basics of differential pressure flow transmitters is essential for anyone working in industries where accurate flow measurement is critical. By knowing how these devices work and the different types of primary elements available, engineers and technicians can select the right flow transmitter for their specific application. Differential pressure flow transmitters play a crucial role in ensuring the efficient operation of flow systems and are indispensable tools for maintaining process control and optimizing performance.

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