Tag Archives: air pressure

Vacuum-Sealed Culinary Preservation and Preparation

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities, and you.

Vacuum-Sealed Culinary Preservation and Preparation

Vacuum sealing protects and preserves food and other perishable products. Both edge-style and chamber-style vacuum sealers are used for this process.  With chamber-style vacuum sealers, the negative pressures in the chamber and inside the bag are nearly always the same. These vacuum sealers also enable special culinary techniques including vacuum-compression or vacuum-infusion.

The vacuum sealing process simply consists of placing the food inside the chamber and closing the lid. Reducing the pressure to 5–50 mbar and then sealing the bag produces a tightly sealed package for most solid foods. A vacuum level of 50 millibars removes about 95% of the atmosphere and at 5 millibars about 99.5% of the air inside the chamber and packing is gone.

A unit like the VacMaster PRO350 Professional Vacuum Sealer has a control panel with pre-set vacuum settings and a digital display of the vacuum level for easy operation. In contrast, the VacMaster VP320 Counter Top Commercial Chamber Vacuum Sealer has a gauge to provide visual feedback to the operator.

VacMaster PRO350 Professional Vacuum SealerVacMaster VP320 Counter Top Commercial Chamber Vacuum Sealer

Note the digital display (a)  and mechanical gauge (b) on these chamber-style vacuum sealers. Source: VacMaster.

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The Pressure in an Iron Lung

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities, and you.

The Pressure in an Iron Lung

Before today’s respirators, patients with several breathing problems relied on a machine called an iron lung. Unlike the modern respirators that use positive pressure (greater than 1 atmosphere) that force air into the lungs, the iron lung was a negative pressure ventilator. The machine surrounded the person and the sealed cavity’s pressure was reduced to induce inhalation by the patient and then the pressure was increased to 1 atmosphere (15 psi or 750 mmHg). While all but obsolete today, these types of machines were extensively used when patients with polio were treated because of loss of muscle control that extended to their ability to breath. Thankfully, Dr. Jonas Salk discovered a vaccine to prevent polio (in 1953) and subsequent vaccines have eliminated polio as a health problem and today positive respirators using microelectromechanical systems (MEMS) pressure sensors can be so small that they are portable.

Iron Lung

The pressure gauge in this iron lung has been replace in modern respirators by MEMS pressure sensors. Source: Pittsburgh Post-Gazette website.

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Widget Pressure

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities, and you.

Widget Pressure

Inside a can of Guinness and a few other beers, a plastic widget releases pressure when the can is opened and exposed to atmospheric pressure. While the process is explained briefly and to the extent that a typical beer drinker cares to know on the can, there are a few other compelling technical aspects that someone involved with or interested in pressure sensing might want to know.

For one, the widget is a patented approach to solving a problem that a canned stout beer, like Guinness, has compared to typical lager or lighter beer or ale. For the later types, carbonating the beer with carbon dioxide (CO2) is sufficient to give the beer its expected head when the beer is poured. In contrast, Guinness and some other beers are expected to have a smoother head. With a widget in the can, these beers have the desired, much creamier, longer lasting head that the draft version has.

The 3-cm diameter widget looks like a ping pong ball but it has a laser-drilled, 0.61-mm pinhole in it. In the canning process, in addition to filling the with CO2 and nitrogen (N2) supersaturated stout, liquid N is added to the stout at the end. The liquid N boils off during pasteurization, the top of the can pressurizes and forces the stout into the pod until equilibrium is reached at about 25 psi.

Mug of Beer with widget

When the can is opened, the pressure is released and the small amount of beer in the cavity rapidly escapes through the pinhole providing sufficient agitation to reproduce the tap handle character for the beer. Enough of the technical stuff. It’s time to verify the results.

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Pressure for an Uplifting Experience

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities, and you.

Pressure for an Uplifting Experience 

When heavy objects need to be lifted, it is common practice to use hydraulic pressure to move them into place. Applications include trucks, diggers, dumpers, excavators, and bulldozers as well as hydraulic cranes. Cranes can lift shipping containers or heavy objects onto buildings or other places. Other applications include something as simple as lifting a garbage receptacle to dump its contents into a refuse truck – a semi-automated process. Of course, the amount of pressure available determines how much weight can be lifted. In some cases, the pressure could be perhaps 34.5 bar (500 PSI) or less. In other cases, it could exceed 689.5 bar (10,000 PSI).

Monitoring the pressure is part of the safety required to avoid accidents from lifting excessively heavy loads and exceeding the limits of the hydraulic system. It can also be helpful in identifying leaks in the system. However, it takes a special type of pressure sensor to be able to interface to the hydraulic fluid and withstand both the chemical and the temperature aspects of the application.

Hydraulics & Pneumatics common pressure bar

The common 1970’s pressure level of 150 bar (2,176 psi) has increased above 450 bar (6,527 psi) since 2010. Source: Hydraulics & Pneumatics.

A hydraulic truck crane that uses counterweights on the back of the cab to keep it from tipping over can have a counterweight gear pump that generates 96.5 bar (1,400 psi). This is much lower than the main pump pressure of 241 bar (3,500 psi).

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