Out of this World Pressures

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 be discussing pressure outside of our blue planet.

Out of this World Pressures

The earth’s average atmospheric pressure is 1 bar (101.3kPa, 29.92 mm Hg or 14.69 psi). Temperature and altitude are among the factors that cause variations. At a specific location, the air pressure can vary about 10%. Leave this planet, where we have the weight of a life-producing atmosphere of oxygen and nitrogen exerting pressure on us and the situation is quite different.

In outer space, the pressure is 1.322 × 10-11 Pa – essentially zero, since there is very little air and hardly any water.

Our nearest neighbor, the moon, has a surface pressure at night of 3 x 10-15 bar (or 3 x10-10 Pa). In contrast, Mars has a layer of gases surrounding it composed mostly of carbon dioxide. As a result, the atmospheric pressure on the Martian surface averages average  750 Pa (0.109 psi) or about 1/100 of the Earth’s. At any given location on Mars, the air pressure can vary by as much as 50%.

Earth’s pressure variations at a given location seem small compared to these other locations. Measuring earth’s pressure variations is also quite easy and commonly performed with a 100 kPa absolute pressure sensor.

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The size difference between Earth and Mars is minor compared to the atmospheric pressure difference. Image courtesy of NASA.

What do you think/Comments?
Do you have a pressure sensing question? Let me know and I’ll address it in an upcoming blog.
-Han Mai, Senior Marketing Specialist, All Sensors Corporation (hmai@allsensors.com)

Jumping for Joy Over 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. In this blog we’ll discuss air pressure and safety in bounce houses.

Jumping for Joy Over Pressure

When the weather is nice and a special event warrants a bounce house, kids get a first-hand experience of the importance of pressure. The air-filled chambers allow bouncing, falling and a lot of fun. Maintaining the pressure requires a pump to run continuously and usually the required pressure is not measured or displayed because it has been predetermined in pre-production design and testing. Unlike a thick rubber tire, the relatively thin vinyl material of the bounce house only requires a few psi to elevate it above the hard ground. With names like Cloud 9 and Jump for Joy as suppliers, it is easy to see how the inflated structure takes children away from the normal day-to-day realities. However, safety is still an issue.

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When safety in a bounce house is discussed, it usually involves parts per million (ppm) of potentially toxic materials  including lead or human contamination. According to one source’s analysis of a specific product, “Lead levels in the vinyl, the tests found, varied from 5,000 parts per million to 29,000, far above the federal limit of 90 to 300 parts per million.” Fortunately, pressure problems are not a concern, since under or over inflation are easily observed by both visual and audible (the pump’s noise) human sensing.

What do you think/Comments?
Do you have a pressure sensing question? Let me know and I’ll address it in an upcoming blog.
-Han Mai, Senior Marketing Specialist, All Sensors Corporation (hmai@allsensors.com)

Sleep on a Layer of Pressurized Air

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 discuss air pressure in mattresses and air beds.

Sleep on a Layer of Pressurized Air

Air mattresses and air beds use air pressure to provide an adjustable comfort level to users.  An air mattress can be easily stored in a small amount of space when it is deflated and brought back into service by “simply” inflating it.

For users that do not want to use lung power for the inflation process, how much pressure should be applied? Most manufacturers seem to recommend something around 1 psi maximum. For measurement purposes, a 5 psi pressure sensor can easily handle this range.

The pump can be built in or external to the mattress or bed. One inflator pump supplier offers a high-volume, low-pressure inflation with a pump pressure of 52 psi and pump volume of 3047 cubic feet/minute. With 1 psi as a max setting, the mattress can be filled quickly and its rating easily exceeded.

However, with this low level of internal pressure, barometric pressure can impact the feel and comfort level and even the life of an air mattress. One manufacturer recommends, “Partially deflate your mattress when leaving it inflated during the day, especially when in a car or tent on a hot day. (Barometric pressure and significant changes in weather and temperature will affect your air mattress’s inflation and possibly damage it.)

Air beds that have a dial setting where the user can determine his or her ideal comfort level may have an inappropriate setting if the weather changes significantly.

According to its website, “Comfortaire designed the first air bed over 28 years ago.” One of their beds even has a psi reading to determine the right comfort level.

With air pressure providing the desired comfort level, the old saying of “sleep tight” may need to be rephrased to “sleep at your ideal pressure.”

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Figure courtesy of Comfortaire.

What do you think/Comments?
Do you have a pressure sensing question? Let me know and I’ll address it in an upcoming blog.
-Han Mai, Senior Marketing Specialist, All Sensors Corporation (hmai@allsensors.com)

The Pressure Impact from Higher to Lower Altitudes

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 discuss pressure and the difference in impact from high to lower altitudes.

The Pressure Impact from Higher to Lower Altitudes

If you have ever driven from a high altitude, say 5000’ above sea level to about 1000’, and you have a flexible sealed empty bottle in the car, at some point, you notice the creaking sound as the bottle collapses due to lower atmospheric pressure sealed inside and higher atmospheric pressure outside.  With the sound effect, the pressure increase on the sealed bottle taken from higher to lower altitude is quite noticeable. Obviously the pressure decreases (externally) during the reverse process and a gas tank (or other similar sealed vessel) taken to a higher altitude winds up visibly expanding.

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This is just one example of the impact of altitude pressure. Athletes performing at higher altitudes know that the altitude affects their performance, especially their endurance, since high altitude (HA) causes faster and deeper breathing. Altitude also affects sleep and cardiac output, so those accustomed to living at lower altitudes need to take appropriate precautions to adjust to the change. Training at higher altitudes can actually enhance the performance of athletes when they compete at lower altitudes.

Humans aren’t alone in their need to adjust to altitude. Internal combustion vehicles must adjust to altitude as well. When electronics was first used to adjust spark and fuel to reduce emissions and improve fuel economy, carmakers used barometric pressure sensors to adjust for altitude.

The pressure change from one altitude to another can be calculated by calculating the pressure for each altitude and then subtracting.  Air pressure above sea level is:

p = 101325 (1 – 2.25577 10-5 h)5.25588

where,

p = air pressure (in Pa)

h = altitude above sea level (in m)

What do you think/Comments?
Do you have a pressure sensing question? Let me know and I’ll address it in an upcoming blog.
-Han Mai, Marketing Coordinator, All Sensors Corporation (hmai@allsensors.com)