Controlling Building 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 proper indoor versus outdoor pressure in commercial buildings.

Controlling Building Pressure

Proper indoor versus outdoor pressure is important in commercial buildings. When indoor pressure is less than the outside pressure, outdoor air leaks, or infiltrates into the building. In addition to impacting heating, ventilation and air conditioning (HVAC) effectiveness, excessive infiltration can also cause uncomfortable drafts, especially in stairways, as well possible odor migrations and even encourage microbial growth depending on the outside weather conditions.

The opposite pressure condition, exfiltration, occurs when indoor pressure is greater than the outside pressure, indoor air leaks out of, or exfiltrates from the building. Excessive exfiltration negatively impacts temperature control by reducing supply airflow into occupied spaces, makes opening and closing doors difficult and creates noisy high-velocity airflow around doors and windows.

In addition to the operation of its mechanical ventilation system, a building’s pressure can be positive or negative due to the impact of wind and weather. Using either a return fan or a relief fan, for direct control of building pressure, manages the combined effects of weather, wind, and mechanical ventilation. This control requires pressure sensors mounted inside and outside of the building to determine the actual pressure difference. Depending on the desired exfiltration and infiltration goals, the pressure difference is typically less than 0.1-inch water gauge (wg) and can be either positive or negative.

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 Sensors’ Role in Solving Drought Problems

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 the importance of pressure sensors’ role in solving drought problems.

Pressure Sensors’ Role in Solving Drought Problems

Sensors play an essential role in preventing excessive water usage and reducing water consumption to minimize the impact of drought situations. Of course there are many actions to conserve water that users can implement that do not involve sensors, but sensors can:

  • Determine if crop irrigation is sufficient to prevent over watering – soil monitoring through rain, temperature, wind, moisture sensors and more.
  • Detect leaks to avoid unnecessary water usage.

Pressure determines the flow rate and consequently the amount of water that is consumed so reducing the water pressure is a common conservation recommendation. Pressure regulators have a built-in pressure sensing mechanism.

Leak Detection

A common technique to determine if a system has leaks has three steps: pressurize the system, isolate the system from the pressure source and then measure the pressure to determine if a pressure drop occurs within a given amount of time. For residential and commercial water users, this would mean adding a pressure sensor to a system that already can measure unnecessary flow.

The utility’s water meter can identify water consumption with its low-flow indicator. Water flow when all water usage is turned off indicates leaking faucets, toilets, irrigation valves or even leaky pipes. Some estimates blame undetected water leaks for 5 to 15% of a private residence’s water consumption.

With today’s wireless technology and sophisticated computing capabilities, pressure sensing could become a tool for utilities to monitor their distribution networks to detect and identify the location of leaks before they become obvious geysers and floods. Researchers in Barcelona, Spain have been investigating this distributed pressure sensing approach for several years.  Using the proper number of appropriately placed pressure sensors in the distribution network generates a leakage signature that allows leakage localization. The leakage detection procedure compares real pressure and flow data with estimates using a simulation of the mathematical network model.  Genetic Algorithms allow the system to generate solutions to leakage problems in a much shorter timeframe than existing approaches.

With water conservation becoming more and more of an issue, both users and suppliers need to take the appropriate steps to ensure future availability. Pressure sensors could be a major part of the solution.

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])

Using WEBENCH for Designing Pressure Sensing Circuits

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 WEBENCH and how it can help design a pressure sensing circuit.

Using WEBENCH for Designing Pressure Sensing Circuits

The WEBENCH Design Center from Texas Instruments provides several online techniques to simplify interfacing pressure sensors and other products. By selecting the Sensors option from eight possibilities on the homepage, then the SENSOR AFE (analog front end) from the pull down Sensor Tool menu and then Pressure from the eight sensors options, you access a list of pressure sensor manufacturers and part numbers with over a dozen parameters identified.

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Selecting a specific sensor such as the 1 INCH-G-BASIC sensors from All Sensors Corporation leads to a screen with the LMP90100 and the selected sensor. With this screen you can select from nine application parameters and see the performance of the design. The LMP90100 is a highly integrated, multichannel, low-power, 24-bit Sensor AFE. Estimated device performance of the sensor and AFE combination is indicated by Input Referred Noise, ENOB (effective number of bits), NFR (noise-free resolution), Current, and Device Error. Pulldown menus and tutorials allow you to modify several aspects and hone in on the right design.

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Another design path starts by selecting the Sensors option from eight possibilities on the WEBENCH Design Center homepage, then Sensor Designer from the pulldown Sensor Tool menu and then Pressure Sensor Amplifier Design from the three options. When you press start design, you access the WEBENCH®Sensor Designer. Once again, you can select the sensor supplier and the sensor for a specific application. For this tool, you can narrow the search to a specific sensor supplier from four suppliers. For example, selecting All Sensors Corporation provides a list of 21 products ranging from 1-inch of water to 15 psi to select from.

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Selecting a specific sensor provides a list of key parameters for a standard product and you have the option of modifying parameters to create a custom sensor. For ease of availability, the best choice is the standard device. This leads to screen with an ADC and amplifier selected for the sensor and additional information as shown below.  However, you have the ability to modify many of the design parameters. Once you are satisfied with your choices, you even have the ability to obtain documentation and a prototyping kit.

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WEBENCH provides sensor system designers a great starting point, design options and a simplified path to evaluating system performance.

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’s Role in Predicting Weather

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 how pressure helps predict weather.

Pressure’s Role in Predicting Weather

With all the harsh winter weather occurring recently, knowing what to expect in your area is important knowledge for short term planning and, in some areas such as the northeast, for long term planning. Sensing barometric pressure was one of the earliest forecasting tools and continues to be important today.

One website provides the barometric pressure history from numerous major cities in the U.S. from Friday, Feb 20 to Thursday, Feb 26. The high and low readings only tell part of the story. The intensity of the weather depends on how quickly the front develops and other factors.

City Highest pressure in period (In. Hg) Lowest pressure in period (In. Hg)
Boston 30.55 29.55
Minneapolis 30.8 29.65
Denver 30.35 29.75
San Francisco 30.35 29.85
Chicago 30.7 29.7

In stormy weather, the barometric pressure tends to be lower and a lower reading is one sign of approaching inclement weather.  During fair weather, the barometric pressure is typically higher and if the pressure begins to rise, it is a sign of tranquil weather.

According to the webpage CHANGES IN ATMOSPHERIC PRESSURE, the barometric pressure is reduced through several processes:

  • The approach of a low pressure trough
  • The deepening of a low pressure trough
  • A reduction of mass caused by upper level divergence (vorticity, jet streaks)
  • Moisture advection (moist air is less dense than dry air)
  • Warm air advection (warm air is less dense than cold air)
  • Rising air (such as near a frontal boundary or any process that causes rising air)

In the U.S., the Federal government uses pressure as part of several methods available to predict weather. On Feb26, the weather in many places around the U.S. was much less severe than it had been in recent weeks with at least one exception.

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THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH AND CENTRAL NEW MEXICO.

  • Humidity 63%
  • Wind Speed SE 20 mph
  • Barometer 30.04 in. Hg. (1017.6 mb)
  • Dew point 17°F (-8°C)
  • Visibility 9.00 mi
  • Wind Chill 15°F (-9°C)

For weather forecasting and other sensing applications, accuracy and other factors make the measurement acceptable for reliable use. That is where the expertise of the user comes into play.

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])