Wireless Weather Instruments - A Buyer's Guide
Author: Frank Ross
For dedicated weather watchers, wireless weather instruments are the ultimate for convenience and putting highly accurate information at your fingertips. The only question that needs to be answered is how much information do you want?
Basic units start with a simple external/internal temperature monitor with a built in clock, and go all the way up to multifaceted displays like the Touch Screen Pro Weather Station. Options for remote wireless data include barometric pressure, wind, rain, and temperature, but you can also get features such as alarms to notify you when preset thresholds are met for indoor or outdoor temperature or barometric pressure, as well as an alarm to wake you up to enjoy the day’s weather.
Before you purchase a piece of weather monitoring equipment, consider your expectations and future expandability. Not all units have unlimited capabilities. If you want to monitor the wind, as well as have a remote rain sensor, or the ability to add additional temperature sensors you’ll need to select a unit that comes with these capabilities, or one that allows you to add additional features as desired.
The heart of wireless weather systems is a small microprocessor, or microcontroller, that gathers and processes the electronic data and then sends a signal via a radio transmitter to an indoor receiver that routes the information to the appropriate portion of the Liquid Crystal Display (LCD) screen, where it can be viewed and evaluated. Unlike traditional bulb thermometers, that use expanding liquids such as mercury to sense changes in ambient heat, with electronic thermometers the most common sensor is a thermoresistor (or thermistor). This device changes its resistance with changes in temperature. A microprocessor or microcontroller measures the resistance and converts it to a temperature on either the Fahrenheit or Centigrade scale. A piezoresistive pressure sensor that also interfaces with the microcontroller is the most common method of measuring barometric pressure.
Barometric pressure measurements are a very effective method of predicting the weather; however, you don’t have to be a weather person to use one of these units. Internal software measures the amount of change, and the speed of change. Those measurements are analyzed by internal software and general icons are displayed for the most probable outcome.
Like they say, timing is everything and internal clocks are another feature that adds value to a wireless weather display. Some units have simple clocks that require the user to set the time, but more sophisticated models automatically download the time each night, from a radio signal transmitted by the atomic clock project in Boulder, Colorado. The atomic clock makes automatic adjustments for daylight savings time and enjoys accuracy of +/- 1 second and you never have to worry about setting it again.
Hunters and fishermen, in tune with the effects of the moon on game movement and fish feeding cycles, will appreciate the models that provide lunar phase information as well as sunrise/sunset times. With this invaluable information close at hand, you’ll never have to scramble to find out when legal shooting hours begin, or wonder was it a full moon last night or was that last week?
Simple LCD thermometers that you can attach to a window are available, but you need to have a window that won’t be in direct sunlight and this location may not be in the most convenient part of your house for easy access. With wireless units you have the option of placing the receiving weather station anyplace within 150 to 330 feet or more (depending on the particular unit you select) from the remote sensing unit, and moving it when the need arises. Location and distance between transmitter and receiver is a critical issue, and one that should be considered before making a purchase, depending on the design of your home and surrounding environment.
When a unit’s broadcasting/receiving capability is listed as 330 feet, that number does not includes the resistance of natural and manmade barriers. For example, an exterior wall has a resistance of approximately 30 feet, and an interior wall has a resistance of 20 feet, on average. Throw in some dense shrubbery outside, or a wall covered by a bookcase and the numbers get larger. Add up all of the wall resistance for location you’ve chosen, and when you subtract that number from 330, you’ll know just how far you can place the remote unit outside.
Where you place the sensing units is also an important factor. Temperature sensors need to be placed in a shielded, dry location that will not be affected by the direct rays of the sun. Generally, fog or mist won’t harm temperature units, but being soaked by rain will end your meteorological pursuits. For rain measurement, place the sensor in an open area, away from tall objects that have the potential to affect the moisture gathering potential of the unit. Trees and tall buildings will block the fall of windblown rain, in effect, casting a moisture shadow over your unit if it is placed too close. A rule of thumb is to place a rain sensor at a distance that is greater than the height of any objects that may be close.
Wind sensors offer a similar opportunity, if you are to enjoy maximum performance from all points of the compass. Any obstruction that alters or diminishes the wind has the potential to degrade the accuracy of the measurements being taken. Height is often the best solution for wind measurement. If possible, place the wind-measuring sensor in an elevated location so that no matter which way the wind blows you’ll have an accurate reading. Another recommendation would be to attach a perch above the unit. Birds tend to perch on the highest point available and you definitely don’t want a bird using your anemometer for a resting spot.
Most units have a simple setup procedure that is controlled by a selecting the various options with buttons on the face of the unit; however, state of the art technology is available with touch screen access that makes it even easier. Models with backlit LCDs make reading the display much easier at night.
Another feature to consider is how you’ll actually use the data that is gathered. Basic units tell you what is going on right now, while more sophisticated units track history, and give tendencies based on historical readings. Top-of-the-line units have the ability to connect directly to a PC, where data can be managed and stored for later long-term analysis. Once you move up the ladder to more sophisticated units, weather forecasting is possible.
By tracking barometric pressure, relative humidity and wind speed, you’ll have enough information to know what’s going on as well as what possibilities the future has in store for your outdoor activities. Even on inexpensive models, you will find weather forecasting functionality that is surprisingly accurate. Naturally, the more information that is entered into the analysis of future weather, the more accurate the prediction. If you’re a stickler for accuracy, select a unit that measures and displays relative humidity, and dew point as well as temperature. A very useful feature of units that measure the wind is the ability to project the effects of wind chill. By analyzing the wind speed, temperature and moisture content, you can know just what it will actually feel like once you step outside.
Weather is the one element of our lives that has the most profound and daily affect on our lives, so it’s not unreasonable that we spend quite a bit of time checking on existing conditions and the predictions for the future. When you have your own weather instrument at your disposal it’s a lot more fun and certainly more convenient. With a wireless weather station, you’ll find yourself checking the data frequently. To date, home-based radar isn’t affordable, but who knows, someday...