TECHSTAR BLOG

The Definitive List of Pressure Measuring Instruments

Posted by TechStar on Nov 18, 2021 9:15:00 AM

Pressure measuring instruments are diverse, with each of them having different capabilities to suit your requirements in measuring pressure values under various conditions.

Measuring pressure – one of the most variable parameters – enables the processing and manufacturing industry to understand the nature of gases, water, and other types of liquid. That is why pressure measurement equipment, including absolute pressure transmitters, are integral in controlling and monitoring gases and liquids.

Depending on your industry and the particular processing requirements involved, having a wide selection gives you the option to choose the most efficient instrument. Some of these devices combine absolute and relative reading, while others take the environment into the equation.

Piezometer

When you want to measure the static pressure head of a flowing liquid at any section of a pipe, you should use a piezometer. This device has one of its tubes exposed to the atmosphere, while the other lower end's mounting is flush with the pipe's inner walls.

Piezometer has a few limitations, though, such as:

  • Difficulty in measuring high pressures
  • Unable to work for negative gauge pressure
  • Ineffective when measuring rapid pressure changes

Manometer

Manometers are pressure gauging instruments used in columns of different liquids, but they can also measure pressure gases. They come in several designs, such as U-shaped, single-column, and inclined tubes.

When one limb is open to the atmosphere, the device can gauge the pressure of the source connected to the other limb. On the other hand, if both limbs connect to pressure sources, it records the difference instead.

Bourdon Gauge

Aside from being suitable for measuring high pressures, the Bourdon gauge is also a good choice if you want to measure negative or vacuum pressures. Calibrating the Bourdon gauge requires having to subject it to numerous known pressures.

One end of this device is a closed metallic tube, elliptical in shape, while the other connects to the gauge point involved in the pressure measurement. The tube will tend to straighten as fluid enters it.

Diaphragm Pressure Gauge

A diaphragm pressure gauge works in a similar principle as the Bourdon gauge. However, it is best for measuring relatively low pressures. Instead of the Bourdon tube, it makes use of a corrugated diaphragm. After attaching the instrument to any gauge point, the diaphragm undergoes elastic deformation.

To indicate the pressure once a deformation occurs, it sends a signal to a pointer by moving on a graded scale. In this regard, a diaphragm pressure gauge also works like an aneroid barometer.

Barometer

When measuring local atmospheric pressure, the barometer is the ideal device you should use. Not only is it one of the essential instruments for companies focusing on weather prediction and forecasting, but some home and business owners also use it to check constant air pressure changes in their properties.

A mercury barometer usually consists of a glass tube about one meter long, closed at one end, and filled with mercury. When a small amount of mercury drops into a bowl, a vacuum takes shape at the upper end of the tube. What supports the mercury column in the tube is the atmospheric pressure acting on its surface in the bowl.

Below are two different subtypes of the barometer:

  • Aneroid barometer: This instrument uses a partially evacuated, corrugated box with a strong spring – preventing it from collapsing. Any variations in pressure cause the front part of the box to deform, resulting in the spring resisting the force of atmospheric pressure.
  • Siphon barometer: This device, also known as a household barometer, has a glass tube bent at the lower part forming a U-tube. It has an enlarged open end which acts as a bowl similar to the ordinary barometer.

Micro Manometer

A micro manometer works using the same principles as a manometer. The main distinction between the two is the suitability of micro manometers for minimizing capillary effects and meniscus reading errors. Its centrifugal form is the best option when you want a high-accuracy reading since its calibration involves pressures of 10 down to 3 mbar. This instrument can detect the null position when the oil droplets sprayed into its glass chamber cease to move.

Why Use Pressure Measuring Instruments

Regardless of the device type used, the reason behind choosing them are almost always identical, such as:

  • Maintains the quality of the products

  • Addresses safety concerns for the unit and operation

  • Ensures machine efficiency

These devices are crucial in avoiding explosions by allowing you to control the pressure. Even if the possible negative impact does not involve any detonation, using these instruments can help with your machines' longevity.

A Pressure Measuring Instrument for Every Requirement

These pressure measuring instruments have their unique variations, but the working principles remain the same. Apart from their specific applications, choosing the type may vary depending on how you gauge the pressure, whether direct or indirect.