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What does a psi matter anyway?

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. In this blog we’ll look at why a PSI or two matters.

What does a psi matter anyway?

Underinflated footballs created a viral controversy before Super Bowl 2015. Measurements of air pressure of 10.5 pounds per square inch (psi) instead of the minimum 12.5 were the issue. Rather than just talk about the issue (a.k.a. Deflategate), engineers performed calculations and more. One company conducted experiments as well.

In its testing, HeadSmart Labs found that on average, footballs dropped 1.07 psi from temperature change in a 75°F room to a 50°F room. Exposing the football to water resulted in an additional 0.75 psi pressure drop. With the combined effects, the footballs’ pressure decreased by an average of 1.82 psi to a max of 1.95 psi.

Richard P. Binzel, professor of planetary science at MIT, calculated that a 5 to 10% drop in temperature could create a drop of 0.5 to 1.5 psi, in a football’s air pressure. Equally important, he noted that the accuracy of the meters used to measure the footballs is unknown.

The bottom line for this or any critical pressure measurement is that for accurate measurements, especially at lower pressures, temperature changes are among the operating environment aspects that should be taken into account and accurate meters need to be used.

What do you think/Comments?
Do you have a pressure sensing question? Let me know and I’ll address it in an upcoming blog.
-Dan DeFalco, Marketing Manager, All Sensors Corporation ([email protected])

Pressure Required for Pick and Place Equipment

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

Pressure Required for Pick and Place Equipment

In the factory, pressure provides essential feedback for many operations. The measurement ensures both proper execution and accuracy of the process. One example is a pick and place station. In this case, a negative pressure (vacuum) lifts an object so it can be located on a work in process (WIP). If the object is not lifted for whatever reason (missing, broken, etc.), the sensor’s reading identifies an error so the WIP does not proceed to the next station. If the normal lifting pressure reduces over time due to leakage, wear or some other cause, the pressure reading can warn an operator to perform maintenance or initiate further machine diagnostics rather than have several defective operations occur.

To create the vacuum, the pump requires energy and time to build to the right pneumatic level. It also takes time to empty the pick and place tool when it has to release the object. These factors all lead to a pump and operating point selection. Typical operating levels will vary based on the application and can range from low to high PSI pressures.

Do you have a pressure sensing question?
Let me know and I’ll address it in an upcoming blog.
-Dan DeFalco, Marketing Manager, All Sensors Corporation ([email protected])

Pressure Sensing in Healthcare

When we’re young, it seems that the thermometer is the essential measurement to determine well versus sick. As we age, pressure becomes increasingly important. Initially, it determines a proper blood pressure level—with less than 120 over 80 (mm Hg) being the desired range.

Proper eye care involves glaucoma testing that uses pressure to determine the onset of this disease. Normal intraocular pressures average between 12-22 mm Hg.

A common tool for detecting the onset of respiratory problems is the spirometer or pneumotachograph. In this case, the reading is airflow rate calculated from a change in pressure drop (∆P) during inhaling and exhaling and can also be used for indirect measurement of lung volumes and capacities. The actual differential pressure measurement is quite low, typically requiring a sensor with as low as ±500 P (±3.75 mm Hg) range to obtain acceptable resolution.

These are the more common pressure measurements that separate a heathy from a sick person. Those with health problems may learn the difference between in vivo and ex vivo pressure measurements, and the use of pressure measurements in respirators, ventilators and more.

Tire Pressure: Not all Measurements are the Same

The proper tire pressure in passenger cars and trucks provides optimum safety and efficiency. Since drivers did not check tire pressures as frequently as they needed to, the U.S. Department of Transportation’s (DOT’s) National Highway Traffic Safety Administration (NHTSA) Transportation Recall Enhancement, Accountability, and Documentation (TREAD) Act of 2000 requires a tire pressure monitoring system (TPMS) on every new vehicle (all passenger cars and light trucks under 10,000 lbs. Gross Vehicle Weight) sold in the U.S. after November 2006.

Not all tire pressure measurements are the same. Car tire pressures are typically 30 to 35 psi with truck values running slightly higher. If you have an ATV, the tire pressure could be more like 8 psi max with some being as low as 2.7 psi and some as high as 10 psi. If you ride a road bicycle, the pressure can range considerably and depends on your weight with tire pressures of 95-105 psi for 110# riders to 125-135 psi for a 230# rider suggested from one source.

You can find tire pressure measurements in some unusual places. The Shipwreck water slide at SeaWorld uses large tires to carry several riders. The tire bumps into the sides of the slide to provide added excitement to the ride. For safety purposes, a maximum rating of 2.9 psi or 0.2 bar is recommended.

The variety of tire pressure readings means that a single pressure sensor cannot provide the required accuracy and precision for all applications.