While the original pressure manometers were very simple devices to accurately measure the force per unit area, the instruments of today are sophisticated enough to provide very precise reading to the level required for testing and research.
The most common design with the original type of pressure manometer was the U-tube. This was typically made of glass and provided gradient markings along the sides of the tube from the bottom of the bend through to the top of each side.
When the tube is left with both of the ends open, the liquid in the tube will be at equal places on both of the “legs” or the upward portions of the tube. When a positive pressure is applied to one side, the liquid moves to the center of the U and up the other leg to the corresponding level.
The same process occurs if negative pressure, a vacuum, is applied to one side of the U-tube. This pulls the liquid up on that side, resulting in a drop on the other side that can be measured to determine the amount of the vacuum.
The benefits of using a pressure manometer in the well-type design are easy to see. These types of manometers use a well or an extended area on one of the legs, thus preventing the need for measuring at two different legs to calculate the difference.
With different scales used for the measurement and different sensitivities in pressure changes possible, these become highly effective in measuring pressure differentials.
New designs also give the pressure manometer more flexibility for use in the field as well as in laboratory and research facilities. Some models are constructed to be portable, making them a viable option as a multi-purpose device. There are also models that are uniquely designed for use in racks and panels. These models are more typically found in testing labs and facilities.
When choosing a manometer, it will be important to know if the measurement will be required for differential, absolute or gauge versions. Knowing the pressure range for the measurement will also be another critical consideration, as well the design of the device in relation to your other existing equipment.
Finally, it is always important to consider the environment or environments where the manometer will be used. The more diverse these environments may be the more important it will be to verify the model selected is up to the job.
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