The Pasco Wireless Weather Station: Like having your own weather satellite

For almost 2000 years, Aristotle’s ideas about weather were the industry standard. Although our hindsight confirmed that many of the theories Aristotle put forth in his work Meteorologica were in error, the depth and breath of his observations and inferences were truly impressive especially given his lack of instrumentation and the non-non-existant units that an instrument could produce.

While inferences are conclusions about the cause of an observation, when it comes to weather, we want to know the future, not just the present. Predicting weather, although wrought with more than it’s fair share of failures and punchlines, it is a staple of our daily routine.

Time and temperature are two foundations of our universe, with time being a measurement of change and temperature being a relative quantity of atomic motion. Pretty much everything else is wrapped up in those two concepts. But what about the details? The small stuff. The other stuff.

A foundational concept of geology, uniformitarianism, is to discern the past by observing the present. Water erodes land. Wind blows sand around. Ice cracks rock. And gravity tries to flatten everything out. Weather, on the other hand, is predicted by inferring what we think caused what we are experiencing now. This double-inference is especially tricky. Ideally though, with enough data points, we can know the future. Well, at least the short-term weather.

Three hundred years before Aristotle, the Babylonians tried to predict short term weather changes based on the look of cloud and other visible changes. And shortly after Aristotle penned his four tomes on weather theory, the Chinese constructed a 24-part annual calendar based on different weather types.

What was missing, and what kept archaic ideas alive for millennia was primarily the absence of instrumentation and quantitive measurements. Qualitative observations lacked both precision and comparative metrics, and without those it was difficult to generalize descriptions across geography and time.

Breakthroughs were made with the creation of instruments used to measure humidity, temperature, and barometric pressure allowing both discrete measurements and inferred measurements by combining types of data. And as electronic communications increased, so did the ability to compile distant observations and measurements, and to make forecasts with the ability to check one’s work.

By the 1860s the combination of many data points across a large area through telegraph communication made weather forecasting a real thing. The accuracy and scope of predicting the weather made another leap when the instruments were attached to weather balloons and rose through the atmosphere adding a third dimension of accuracy.

The next big break in wether prediction was numerical analysis of the data. What was needed was a formula where the variables could be entered resulting in a solution that accurately predicted the weather at a point in the future. And as the equation was refined, accuracy improved and the reach into the future was greater. Oddly, from Aristotle’s methods of 2300 years ago until 19 years before we went to the moon, using all the math and instrumentation possible, we measured success by predicting the weather a full 24 hours into the future.

Today, we combine all the best of our instruments and equations along with space-based satellites allowing us to predict weather with much more accuracy and much farther into the future. But even that has not dampened weather’s role in jokes and punchlines.

Weather stations of various quality have been part of the science classroom for decades. Beginning with the simple indoor/outdoor thermometer, quantitative weather observations have been a popular part of the daily classroom routine whether morning homeroom or science curriculum from kindergarten to graduate school.

What has changed over recent time is the shape and capabilities of the weather station. From boxes within larger boxes, to individual instruments bolted and wired together, all with their own limitations. One of the biggest challenges is the data collection, well actually the data extraction and visualization. Half of science is data collection. The other half is data interpretation. The former without the latter is useless. The latter without the former is, well, fake news.

The Pasco Wireless Weather Sensor

Pasco has created a unique and intensely feature-filled weather station that contains 17 different measurements or extrapolations. As if that weren’t enough, the quarter-pound of sensors in the Pasco powerhouse can share it’s finding with a computing device through a USB cable, through Bluetooth, or just hang on to them inside its built-in memory until a later time. That means the weather station can transfer it’s weather data, current or over time or both, from a few cabled meters away, like magic through the air via Bluetooth up to 10 meters away, or 12,756 km away using independent datalogging only to be picked up at a later date and downloaded. By the way 12,756 km is the farthest any two points can be from each other on planet earth.

And you can keep track of you place on the earth because the Pasco Wireless Weather Sensor has built-in GPS.

Pasco.com lists the sensors and specs as:

Barometric Pressure

• Range: 225 to 825 mmHg

•Accuracy: ± 0.1 mmHg

•Resolution: 0.02 mmHg

Ambient Temperature

• Range: -40 to 125 °C

•Accuracy: ± 0.2 °C

•Resolution: 0.1 °C

Wind Speed

• Range: 0.5 to 15 m/s (winds of up to ~ 33 mph)

•Accuracy: 3% of reading

•Resolution: 0.1 m/s

Directional measurement

• Wind direction: 0 to 360°

•True heading: 0 to 360°

•Magnetic heading: 0 to 360°

Relative Humidity

• Range: 0 to 100%

•Accuracy: ± 2%

•Resolution: 0.1%

Illuminance (light level)

• Range: 0 to 130,000 lux

UV Index

• Range: 1 to 12

•Accuracy: ± 1

•Resolution: 1.0

Altitude (via GPS)

• Range: 0 to 18,000 m

•Accuracy: 2.5 (50% CEP)

•Resolution: 0.5 m

Speed (via GPS)

• Range: 0 to 515 m/s

•Accuracy: 0.05 m/s

•Resolution: 0.05 m/s

Connectivity

• Bluetooth 4.0 or USB 2.0

Battery

• Rechargeable Lithium Polymer

Data Logging

• At least 30,000 samples with all sensors on

•Up to a full week with GPS sensor turned off

Water-resistance

• Splash proof and designed to withstand the elements

Operating Environment

• – 20 to 150°C

Calculated measurements

• Absolute Humidity, Dew Point, Wind Chill, and Humidex

GPS

• 66 channels

•Warm up time of 35 seconds or less


One essential accessory for the Pasco Wireless Weather Sensor is the Weather Vane Accessory. The three pieces in this kit include a tripod mount allowing free 360 degree spin, a screw-in boom, and a tail fin. By adding 20cm of distance between the Pasco Wireless Weather Sensor and 48 square centimeters of wind-grabbing vertical wing, the Weather Vane will keep the Pasco Wireless Weather Sensor’s turbine anemometer perpendicular to the wind. The kit also comes with a stout table-top tripod with excellent leg-spread and a ball head for quick adjustment and solid lock-up.

The tripod kit also makes an excellent handle that removes any directional bias from simply holding the Pasco Wireless Weather Sensor in your hand and pointing it towards where you think the wind is coming from. Additionally, the stiffness of the metal tripod legs allow it to be form fit to a slanted surface without raising the center of gravity much.

The built-in USB rechargeable lithium polymer battery powers all the sensors, the GPS, and of course the Bluetooth radio that effortlessly transmits the data to any compatible device with Pasco SPARKvue software including those running iOS, Android, ChromeOS, Mac and Windows.

The Pasco Wireless Weather Sensor can directly measure wind speed, wind direction, barometric pressure, humidity, ambient temperature, light level, UV index, and magnetic heading. With that information, the software can calculate dew point, wind chill digital-compass wind direction, absolute humidity, and heat stress index. The on-board GPS receiver can identify latitude, longitude, altitude, speed, wind direction (with declination adjustment) and number of satellites the Pasco Wireless Weather Sensor is listening to.

While most of the measurements are self-explanatory, a couple of them can be confusing. Dew point, for instance, is the temperature to which air must be cooled to become saturated with water so at any lower temperature than the dew point, water condenses out of the air making dew. If the dew point is below freezing, then its called the frost point since frost forms rather than liquid dew.

The relationship between dew point and humidity is that humidity is a direct measurement of the amount of water vapor present in  the air. The higher the humidity, the closer the measured humidity and the calculated dew point. At 100% humidity, the dew point is equal to the ambient temperature.

Wind chill, windchill, wind chill factor, or wind chill temperature; it doesn’t matter what you call it, it is a calculated number below the ambient temperature that considers convective heat loss on a surface similar to human skin. The idea is that ambient temperature alone does not provide general information about how cold it feels, and how the body will react. Convective heat loss can make a temperature behave and feel much colder than if there was little convection. And since convection can easily be countered with modern fabrics and outdoor clothing, and being inside a car, the application of the wind chill factor are mostly limited to those situations where unprotected (direct skin) exposure to the wind can happen.

The calculation of windchill involves wind speed, air temperature and some constants that are generally agreed upon to represent human skin. Over time, the constants have changed, and even today they vary across continents. However, in 2001, the Joint Action Group for Temperature Indices (JAG/TI) updated the wind chill temperature index adding or specifying the following:

  • Use calculated wind speed at an average height of five feet (typical height of an adult human face) based on readings from the national standard height of 33 feet (typical height of an anemometer);
  • Be based on a human face model;
  • Incorporate modern heat transfer theory (heat loss from the body to its surroundings, during cold and breezy/windy days);
  • Lower the calm wind threshold to 3 mph;
  • Use a consistent standard for skin tissue resistance; and
  • Assume no impact from the sun (i.e. clear night sky).

The calculated Heat Stress Index is basically the relation of the amount of evaporation or perspiration required to cool a body compared to the maximum ability of the average person to perspire.  Somewhat similar but opposite of the wind chill factor, the heat stress index uses ambient temperature and humidity along with some assumptions (constants in the equation) to generate a temperature number above the ambient temperature. The Heat Stress Index can kick in at 80 degrees F, and climbs rapidly from there. The concept here is that it takes energy to vaporize (evaporate) water. The human body excretes water through sweat glands and as that water evaporates, energy is lost thus cooling the body. But in order for the water to evaporate, there must be “room” in the air for it. As humidity climbs, there is less and less room until 100% humidity is reached at which point there is no room so essentially the body’s cooling mechanism is completely ineffective. Some examples include at 96 degrees F, the heat index is 108 at 50% humidity, and 132 at 75% humidity. And 90 degrees F, the heat index is 108 at 75% humidity and 132 at 100% humidity. However, 100% humidity at 80 degrees F only yields a heat index of 87. I am using Fahrenheit since most US weather measurements and Heat Indexes are reported in such units whatever we call them now like British, English, SAE, non-metric, fractional, U.S. units, Imperial, or the formal sounding USCS for United States customary system.


The way the instrument works is almost as much fun as using it. For instance, temperature is measured by a thermistor which, like it sounds, is a electrical resistor that changes its resistance as temperature changes. Temp goes up, resistance goes up. Temp goes down, resistance goes down. So when the resistance is calibrated to the temperature, the flow rate of electricity now tells the temperature.

Another chip, the humidity sensor also uses resistance. In this case the electricity flows through electrodes embedded in a water-absorbing resistive polymer material exposed to the air. As moisture (humidity) is absorbed into the polymer, the resistance changes and so does the reported percentage of water vapor in the air known as humidity. Of course you can complicate matters by splitting the hairs of absolute humidity, relative humidity, and specific humidity.

Finally is the turbine anemometer, by far the coolest moving part on the Pasco Wireless Weather Sensor. Like a tiny six-bladed ship’s propeller, the twirling blade spins almost effortlessly inside its tube generating an electric current corresponding to its speed.  And as the only major moving part in the Pasco Wireless Weather Sensor, it is replaceable.

The Pasco Wireless Weather Sensor is controlled by the software on a computing device. Pairing the sensor with Bluetooth allows control over what instruments are monitored, and even to turn some of them on or off. For example, you may want a data collection run over several days, but in the same location. In that case, the power-hungry GPS receiver and power thirsty digital compass can be turned off to substantially increasing the runtime.

The SPARKvue software platform is available from Pasco in any of 28 different languages including Kazakh, Thai and Turkish as well as several flavors of Spanish, French, Chinese, and Portuguese. In SPARKvue, you can build a visual interface that shows up to six of the sensors in real-time. You also have the choice of individual graphs, gages, numbers and other measurement presentations.

Mark Twain once said that, “Climate is what we expect, weather is what we get.” I once said, “If you don’t like the weather here in Montana, wait an hour. It will get worse.” No matter who you quote, teaching about the relationship between current weather, future weather, and the measurements we use to bridge the time gap is not only important, but with 33 hits for the term weather in the NGSS Standards (only 26 for the term Force, but 77 for the term Chemical), I’d label weather as an important science topic in need of attention at all grade levels.

Even in the future when each school district has its own weather satellite, there will still be a need for local measurements, and the simplification of large scale phenomena. Tools such as the Pasco Wireless Weather Sensor will be an invaluable component in making the abstract concrete, the enormous manageable, and the experience quantifiable. Just imagine if Aristotle had his own Pasco Wireless Weather Sensor. We might be two thousand years more advanced than we are now!

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