{"id":14178,"date":"2021-03-25T09:34:04","date_gmt":"2021-03-25T14:34:04","guid":{"rendered":"https:\/\/blog.wika.com\/us\/\/?p=14178"},"modified":"2023-08-22T04:20:41","modified_gmt":"2023-08-22T09:20:41","slug":"low-pressure-gauges-for-very-low-and-vacuum-pressure-measurements","status":"publish","type":"post","link":"https:\/\/blog.wika.com\/us\/products\/pressure-products\/low-pressure-gauges-for-very-low-and-vacuum-pressure-measurements\/","title":{"rendered":"Low Pressure Gauges: For Very Low and Vacuum Pressure Measurements"},"content":{"rendered":"

To accurately measure pressure below 10 psi (690 mbar), mechanical gauges use a capsule element. Capsule gauges are found in applications that operate in a vacuum or pressures as low as 1″ water column. \u00a0<\/strong><\/p>\n

In most Bourdon tube pressure gauges<\/a>, the range limitation on the lower end is 10 psi (690 mbar). Measurements below that call for a different sensing element. A low pressure gauge with a capsule design can go down as low as 1″ H2<\/sub>O (0.036 psi, 2.5 mbar), and measures po<\/span>sitive and negative gauge pressure<\/a>. Capsule elements are also used in other product families, such as differential pressure gauges<\/a>.<\/p>\n

How does a low pressure gauge work?<\/h2>\n\n
\"Capsule

Figure 1: gauge with vertical capsule element<\/p><\/div>\n \n

Low pressure gauges have a very sensitive mechanism consisting of two corrugated discs, each made of brass or stainless steel, that are fused together to create a circular capsule. The slightest changes in pressure cause the capsule to expand or contract; a pinion movement mechanism transfers this motion to the indicator.<\/p>\n\n

\"Capsule

Figure 2: gauge with perpendicular capsule element<\/p><\/div>\n \n

Capsule gauges are cost-effective instruments that measure low pressures very precisely and with accuracies up to \u00b11.0% of span. The accuracy varies according to the gauge\u2019s nominal size. This is because the capsule element is typically placed vertically inside the case, parallel with the dial face (Figure 1). The larger the disc surface area, the better it is able to detect low pressure changes.<\/p>\n

For low pressure gauges with high overpressure safety, the capsule sits perpendicular below the case (Figure 2). As pressure (p) enters the pressure-sealed measuring chamber (1), it deflects the capsule measuring element (2), which transmits the motion to the movement (3) and indicator. The capsule element is supported by the surrounding housing and, therefore, can achieve high overpressure ratings. This design can be found in model 632.51<\/a> (4″ or 6″), and it comes standard with an overpressure safety of 50 times of full scale.<\/p>\n

Applications for low pressure gauges<\/h2>\n

Capsule gauges are found in applications that operate in a vacuum or very low pressures. These include, but are not limited to, the following:
\n\u2022\u00a0 \u00a0Fan and blower monitoring
\n\u2022\u00a0 \u00a0Filter monitoring
\n\u2022\u00a0 \u00a0Low-pressure pneumatic systems
\n\u2022\u00a0 \u00a0Vacuum pumps
\n\u2022\u00a0 \u00a0Medical suction devices
\n\u2022\u00a0 \u00a0Gas burners
\n\u2022\u00a0 \u00a0Overpressure monitoring in clean rooms<\/p>\n

Low pressure gauges are used in a variety of industries:
\n\u2022\u00a0 \u00a0Medical equipment
\n\u2022 \u00a0 HVAC<\/a>
\n\u2022\u00a0 \u00a0Oil and gas<\/a>
\n\u2022\u00a0 \u00a0Petrochemical<\/a>
\n\u2022 \u00a0\u00a0Power generation<\/a>
\n\u2022\u00a0 \u00a0Environmental technology
\n\u2022\u00a0 \u00a0Mechanical engineering<\/p>\n

A low pressure capsule gauge with brass wetted parts is suitable for most applications. For use with aggressive media, choose a stainless steel pressure gauge<\/a>.<\/p>\n

Important note:<\/strong><\/em> Low-pressure capsule gauges can be used only for dry gaseous media. Due to the instrument\u2019s vertical position and the very narrow passage into the capsule element, liquid media won’t be able to drain out completely. Any liquid that remains inside the capsule will create a hydrostatic load, which will result in a false pressure indication. To measure liquid media at very low pressures, use a Sealgauge diaphragm pressure gauge like the 43X.30<\/a>, 43X.36<\/a>, or 45X.50<\/a>.<\/p>\n

Benefits of using WIKA low pressure gauges<\/h2>\n

Because low pressure gauges can be used in a variety of industries, the benefits are equally diverse. Here are some reasons for choosing a WIKA capsule gauge:<\/p>\n