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A Simple Approach To Selecting Differential Pressure Transmitters

The first thing that is evident when searching for differential pressure transmitters is that there is an astounding number of options on the market. Often it is easy to become bogged down in the specifics of each particular design when it is really a big picture overview that is the most effective first step. The Role of the Transmitter All pressure is basically defined as the force applied to an area. With the need for differential pressure measurements what is needed is the difference in pressure, the force on the area, at two different points. There is no standard that the change in pressure is compared to such as the atmospheric pressure or a vacuum. Instead, the difference is the pressure change between the two points. The use of differential pressure transmitters is essential in maintaining system flow, stability and control. These transmitters will measure specific changes in pressure between the two points that is they relayed, in the form of an electronic signal, to the system. This can allow control to maintain the desired pressure differential or ensure there is no difference in pressure between the two points. The Importance of Design While it may seem evident, the use of differential pressure transmitters will often be dependent on the specifics of the system. All of the different transmitters have a primary element, which can be a venturi, orifice plate, tube or a flow nozzle. This actually measures the increase in the flow as the flow at one point increases compared to the flow at the other. The secondary element will be used to measure the change in the differential pressure related to the flow. It will use the data from the primary element, which will be recorded independently of the temperature of the liquid, semi-solid or gas, ambient temperature or the actual fluid...

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The Basics Of Pressure Manometer Designs

While it may seem like pressure measurement is a very modern and highly technical and technology-based application, pressure has been measured for centuries with high degrees of accuracy using very basic types of equipment. One of the first types of pressure manometer designs was the U-tube, which was invented by Dutch scientist and mathematician Christiaan Huygens in 1661. This was followed very shortly by the liquid column manometer invented by Italian physicist and mathematician, Evangelista Torricelli, which in fact is the model for the modern mercury barometer. U-Tube Manometer Basics The U-Tube manometer works on very simple principles as well. The liquid in the bottom of the U moves based on gravity and the liquid’s density compared to the pressure, providing consistent measurements without any need for continual calibration. When equal pressure is applied to the open ends of the tubes the level of the liquid on either side of the tube will be the same. When different atmospheres are on either side of the tube the liquid height in each of the columns of the U-Tube will change. This change can be measured as the difference between the two. Liquid Manometers A liquid can also be used to measure differential pressures. These pressure manometers can use water for small differences or mercury or other specific types of liquids for greater pressures. The specific gravity, the vapor pressure and the temperature range of each of these types of liquids have to be carefully considered when making a selection. Digital Manometers To eliminate the special requirements of the traditional U-Tube, or even the inclined-tube manometers, digital models are now available. These are very accurate and easily be quickly calibrated as needed. Using microprocessors, this modern pressure manometer options are highly accurate and can read to a level not possible with other manometers. Also, since they don’t have the tubes and the liquid concerns, they are more effective across a greater range of environments. The digital manometer can be completely portable or it can be permanently installed. In addition, the use of pressure measuring software can allow for corrections required in different types of applications, eliminating errors in reading and compensating for different factors. While the old style of manually read manometers still have a place and are accurate to the degree needed in many applications, the digital manometer has the ability to take accuracy in pressure measurement to the next...

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