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Weather Instruments

Weather Instruments
Posted in: Measuring Weather
By AcuRite Team
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Weather Instruments

What Are Weather Instruments?

A weather instrument is any device that measures weather-related conditions. Since there are a wide variety of weather conditions that can be measured, there is a large assortment of weather instruments available for many different purposes. You may already be familiar with common weather instruments, like thermometers and wind vanes. But to get the full picture of the weather around us, we need hygrometers, anemometers, barometers, rain gauges and sometimes even lightning detectors. Oftentimes, multiple weather instruments are combined into a single product, known as a weather station. By integrating multiple environmental measurements and a barometer, weather stations can give you a thorough view of the conditions outdoors and also generate reliable weather forecasts. This article explains the various types of weather instruments, how they work and ultimately how they can benefit you on a day-to-day basis.

Personal weather stations provide accurate conditions for your exact location. Perhaps you have a garden and need precise tracking of rainfall? Maybe a warning about impending frost would help you extend your growing season, or give you time to cover up your fragile annuals? Advance notice about high winds would tell you to bring your child's soccer goal inside before it blows down the street. And it goes without saying, the TV weather can’t monitor air conditions indoors in places like your garage, home, attic or basement.

If you want environmental data specific to your own back yard, you need personal weather instruments.

AcuRite’s product lines include a wide variety of wireless weather instruments available for personal use. Before deciding which is the best weather station for your needs, it’s important to gain a general understanding of the types of weather instruments, how they work and what they do.


weather instrument - anemometer
  • Measures wind speed
  • Cups spin with airflow
  • Speed displayed in Mph and km/h
What is an anemometer?

An anemometer is any device that measures wind speed. The first wind measuring devices were invented centuries ago, and several varieties of anemometers have been developed over the years. These various designs have incorporated cups, propellers an even sonic sensors.

AcuRite uses a three-cup configuration that spins horizontally as wind passes through it. This design works well because the aerodynamically designed cups capture the maximum amount of wind force on the open side while allowing the air to easily flow over the back side of the cups turn through their rotation. Another quality feature is a dual bearing design that eliminates shaft wobble and flex, something not offered on other similarly priced weather station systems.

Once in motion, the cups turn a small drive shaft with a magnet at its bottom end. As the drive shaft turns, the magnets pass over sensors, sending electrical impulses to a computer processor. The processor then translates the electrical impulses to a wind speed reading.

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AcuRite’s AcuRite Notos (3-in-1), AcuRite Iris (5-in-1) and Atlas weather stations all feature anemometers, wirelessly delivering accurate wind speed information to an AcuRite weather station display, or to a smart phone or computer using the My AcuRite app.

Wind Vanes

What is a wind vane?

A wind vane indicates the direction the wind is blowing. For example, it can let you know wind is coming out of the Southeast, and then shifts direction to the East.

Wind vanes are fairly simple devices. A fin sits on a spindle that can rotate horizontally. Since it’s longer on one end than the other, the fin will always point in the direction the wind is blowing.

AcuRite weather stations feature a wind vane that is incorporated into its AcuRite Iris (5-in-1).  The wind vane hangs from the sensor’s underside, and rotates on a spindle. At the end of the spindle is a 16-position optical sensor that lets the computer processor know what direction the vane is pointing to generate a wind direction reading. The wind vane’s balanced design and precision bearings let it turn smoothly even when the tiniest of forces are applied. This enables it to sense the slightest shift in wind direction. And like an anemometer, it features a dual bearing design to eliminate shaft wobble and flex.

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AcuRite’s Iris (5-in-1) features a wind vane, enabling it to wirelessly deliver accurate wind direction information to a weather station display, or to a smart phone or computer using the My AcuRite app.
weather instrument - wind vane
Wind Vane
  • Measures wind direction
  • Fin rotates on a spindle
  • Direction displayed as North/South/East/West


weather instrument - barometer
  • Measures barometric (atmospheric) pressure
  • Employs a piezo-resistive pressure sensor
  • Changes in pressure can indicate oncoming storms
  • Pressure displayed in inHg (inches of mercury)
What is a barometer?

A barometer measures atmospheric pressure. As with other weather instruments, many different barometer designs have been developed over the centuries. The most common types historically have been mercury (also known as Torricellian barometer) and aneroid barometer.

AcuRite weather stations feature an electronic barometer. It uses a piezo-resistive pressure sensor, which converts atmospheric pressure into an analog electrical signal. The way it works is that the pressure sensor contains what is known as a strain gauge. Strain gauges used for this purpose are often made in the form of a diaphragm. The greater the atmospheric pressure, the more the diaphragm will deform. Since an electrical current is running through the sensor, a deformation of the diaphragm will yield a change in the electrical resistance applied to the current. This change in current is interpreted as a pressure reading by the digital barometer’s processor. In other words, the higher the pressure, the more the diaphragm moves, and in turn the higher the pressure reading.

Among the array of available weather instruments, barometers are vital because changes in atmospheric pressure can indicate an impending change in the weather—such as a thunderstorm. As such, AcuRite’s weather stations take into account barometric pressure when calculating weather forecasts.

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Barometers are built into AcuRite’s weather station displays, as well as AcuRite’s AcuRite Access™. This helps provide reliable weather forecasts as seen on an AcuRite weather station, or on a smart phone or computer using the My AcuRite app.


What is a hygrometer?

A hygrometer measures humidity. Over the years, methods of measuring humidity have included twisted fibers, wet cloths covering thermometer bulbs and even pine cones.

AcuRite’s humidity sensors use a resistive sensor. The way it works is that electricity flows through a small piece of water absorbing resistive polymer. Since the polymer is exposed to the air, water vapor has the ability to absorb intro the material. This, in turn, changes its resistance to any electric current that passes through it. As you may expect, the higher the humidity in the air, the more water vapor will absorb, and the greater the change in electrical resistance. The resistance applied by the sensor will be electronically translated to a humidity reading on the hygrometer or weather station’s digital display.

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AcuRite hygrometers are built into AcuRite’s wireless temperature and humidity sensors, wireless humidity monitors, AcuRite Notos (3-in-1) and AcuRite Iris (5-in-1) wireless weather sensors, and a variety of stand-alone temperature and humidity measuring products. All wireless sensors are capable of delivering accurate humidity information to an AcuRite weather station display, or to a smart phone or computer using an AcuRite Access™.
weather instrument - hygrometer
  • Measures humidity
  • Employs a resistive sensor
  • Humidity displayed in percentage relative to saturated air

Lightning Detectors

weather instrument - lightning detector
Lightning Detector
  • Senses lightning strikes
  • Counts number of strikes
  • Distance to oncoming storm
What is a lightning detector?

A lightning detector gauges the distance and frequency of lightning strikes. Depending on purpose and technology, lightning detectors can vary dramatically in cost and complexity. They start with your ears and eyes (nature’s original lightning detector) and end with equipment used at airports which may cost in excess of $100,000.

To help enhance safety at ball games, job sites and hiking trips, AcuRite offers reliable, affordable, personal handheld lighting detectors. A personal lightning detector works along the same principles as a radio. The difference is that a lightning detector “tunes in” to the specific electromagnetic pulse (EMP) given off by a lightning strike. Since AcuRite’s personal lightning detectors are also programmed with the ability to analyze various properties of the EMP’s, they can estimate the distance of the lighting strike. In addition, an adjustable filtering system will reject false lightning signals, from microwaves, electric motors and other misleading sources. Since the lightning detector also counts strikes once a lightning storm begins, the user has the ability to gauge the severity of the storm and (using the distance estimates) deduce if the storm is headed toward or away from the user. Battery operated and sized to clip onto a belt or backpack strap, AcuRite personal lightning detectors offer convenience and portability.

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AcuRite personal lightning detectors are available as a stand-alone unit, or as an upgrade to the AcuRite Atlas™.

Rain Gauges

What is a rain gauge?

A rain gauge measures rainfall over a period of time. AcuRite offers two types of rain gauges; analog rain gauges, and digital rain gauges with self-emptying wireless rain collectors. Here is an overview:

Analog Rain Gauges: Incredibly simple, easy-to-use and economical, these devices collect raindrops during a storm and (via graduated lines) tell you how many inches of rain has fallen. Typically, analog rain gauges top out at around five inches and will need to periodically be emptied to continually measure a rainfall that exceeds their liquid capacity. They will also need to be manually emptied between rain events to obtain an accurate measurement of a subsequent storm.

Digital Rain Gauges with Self-Emptying Wireless Rain Collectors: These devices collect rain drops during a storm and wirelessly transmit rainfall data, either to a stand-alone digital display or a digital weather station.

The self-emptying rain collector works by funneling rainfall into a dual-sided “tipping bucket.” The tipping bucket acts like a see-saw, with one side always pointed up. As rainwater collects in the “up” side, it eventually grows heavier and tips over. When it does, it empties out its contents as the other side of the tipping bucket begins to fill with rain water. Each time a bucket tips from side to side, an electronic sensor is tripped. Since each bucket collects a specific amount of water before tipping, the rain gauge will know how much rain has fallen based on the number of times the bucket tipped during a storm.

In addition to improved accuracy, self-emptying rain collectors offer several advantages over analog models:

  • Self-emptying design allows for months of continuous rainfall tracking.
  • Thanks to the wireless transmitter, rainfall data can be viewed remotely, indoors.
  • Rainfall data can be automatically recorded on a weather station or stand-alone digital display.
  • The weather station or digital display often will provide historical data such as high and low records, annual rain accumulation, etc.

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AcuRite's self-emptying rain gauges are available as a stand-alone digital rain gauge or as part of AcuRite’s Iris (5-in-1). Both the Atlas unit and the AcuRite Iris (5-in-1) sensor can wirelessly deliver rainfall information to a weather station display, or to a smart phone or computer using an AcuRite Access™.
weather instrument - rain collector
Rain Gauge
  • Measures rainfall
  • Basic and digital self-emptying models
  • Advanced features include historical records


weather instrument - thermistor
  • Measures temperature
  • Employs a thermistor, bi-metal coil, or liquid in a tube
  • Temperature displayed in Fahrenheit or Celsius
What is a thermometer?

A thermometer measures temperature. AcuRite offers three types of thermometers; tube thermometers, bi-metal coil thermometers, and digital thermometers with thermistors. Here is an overview of all three types:

Tube Thermometers: A tube thermometer’s operation is simple; as temperature increases, liquid contained at the bottom of a glass tube expands, making it rise upward. As temperature decreases, the liquid level falls. A gauge alongside the tube translates the liquid level into a temperature reading.

Instead of mercury, AcuRite’s tube thermometers are filled with 99.7% coal oil and 0.3% red pigment. This combination delivers accurate, reliable performance. It’s also safe in the event the thermometer is broken.

Bi-Metal Coil Thermometers: As the name implies, the design of a bi-metal coil thermometer centers around a coiled metal strip. The strip is actually two plies of metal, with each ply made of a different, specially-selected type of metal. The two metals were chosen because they expand at different rates when temperature rises. The outermost ply will be made of a metal that expands at a faster rate than the inner ply. This creates a “push-pull” between the two strips. In other words, as temperature increases, the outer strip will be trying to unravel the coil while the inner strip will be pulling against it, trying to keep the metal more tightly coiled. The amount the coil unravels will be mechanically translated into a temperature reading on an analog dial. The more a coil unravels, the higher temperature reading.

Digital Thermometers with Thermistors: All of AcuRite’s digital thermometers and weather stations measure temperature using a device called a thermistor. Thermistors are thermally sensitive resistors which change in electrical resistance as temperature rises or falls. To put it another way, the thermistor has an electrical current flowing through it. Depending on the temperature it’s exposed to, the thermistor will make it easier or harder for electricity to pass through…sort of like putting a kink in a garden hose to reduce the flow of water. There are two types of thermistors:

  • Negative Temperature Coefficient (NTC) thermistors exhibit a decrease in electrical resistance when subjected to an increase in temperature.
  • Positive Temperature Coefficient (PTC) thermistors exhibit an increase in electrical resistance when subjected to an increase in temperature.

The amount of electrical resistance applied by the thermistor will be electronically translated to a temperature reading on the thermometer’s digital display. Thermistors are especially useful because (depending on the model and specifications) they can measure temperatures ranging from -100° to more than 600° Fahrenheit. They are also extremely precise over their entire temperature range, resulting in accurate, reliable temperature readings.

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AcuRite’s basic thermometers, indoor and outdoor digital thermometers, and weather stations within the AcuRite Olympus Series™ feature digital thermometers delivering accurate temperature information to an AcuRite display or the My AcuRite app and website. 


Weather Stations: a Combination of Weather Instruments

All of the weather instruments mentioned above can provide vital information. But when their information is combined and analyzed, you get a clearer view of the complete weather picture—and you can also make reliable forecasts. This is why a weather station is a great way to get a comprehensive view of the weather conditions surrounding you. There are many varieties of weather stations available.

How Do AcuRite Weather Instruments Benefit You?

Between your smartphone, the Internet, your TV and the radio, it’s easy to access a weather report. And thanks to satellites, radar and other technology, you can get reliable conditions and forecasts for your general region. What's important to note is that oftentimes the media pulls its weather data from weather stations positioned at the local airport or TV station. But the weather in your own back yard is unique and special. In other words, there are times when accessing conditions by the airport, in the city, or at a TV station 35 minutes away isn't a true reflection of the weather in your neighborhood.

June 22, 2017
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