Wind Anemometers – How to Measure Wind Speed Accurately

For a science that is constantly in the lives of everyday folk, wind speed measurement certainly manages to keep out of the public eye. The measuring of wind speed happens to be an important part of a number of everyday technologies. Of course there is meteorology, the measuring of weather phenomena, that wholly depends on the gauging of wind speed; but a surprising number of other everyday specialties depend on wind speed measurements too, chief among them being aviation and marine and navigation, stability management in skyscrapers, environmental sciences and disaster management. Wind measurement is done with a device known as a wind anemometer; though it might be argued that that is a redundancy since anemometer comes from the Greek Anemos = wind.

Any device that measures wind speed is bound to sense the pressure of it too. For this reason, many anemometer designs are successful when used as pressure meters too in addition. A version of anemometer is known to have existed since around 1450. The modern wind anemometer though, has been around for more than a century and a half now; the first successful design was one that used a structure with four arms fanned out, each one with a cup attached that caught the wind and spun the structure. The inventor, Dr. John Robinson, held the impression when he made his invention that any cup anemometer would share the characteristic that it would spin at a third of the speed of the wind blowing past it, no matter what size it was built to be. Researchers took his word at its face for quite a while before it was discovered that the size of design used always affected the results. Researchers who had used the inventor’s figures for their calculations for years had to start over from scratch.

Cup anemometers, these simple devices, are remarkably accurate machines today nevertheless; the best examples can approach a 99% accuracy level, and still be no more expensive than about $1000. But the cup anemometer is still a mechanical technology that is prone to maintenance lubrication issues, friction, mechanical damage and ice formation. There are competing technologies that attempt to eliminate the problems seen in the mechanical design. One of the most popular wind anemometer technologies in use today is the ultrasonic kind. The principle of the ultrasonic design is this: the speed of sound depends on the speed and the direction of the air that it passes through. A headwind slows sound down, and a tail wind speeds it up. An ultrasonic wind anemometer fires high-frequency sound pulses back and forth between two receivers. If the pulse takes more time travelling in one direction than the other, that is a sign that the slower trip had a headwind working against it. The time differential helps calculate the wind speed. You’ll find these in use on tall buildings, on weather buoys and at weather stations.

Another wind anemometer design that is particularly ingenious is the constant-temperature anemometer. A thin wire held between two electrodes is heated up electrically to hold a constant temperature. A sensor measures the amount of current needed to hold the temperature at ambient temperature levels. Any loss of temperature that is faster than would be explained by the ambient temperature levels would have to come from wind speed. This is a particularly accurate method of measurement of wind turbulence. However, like the laser measurement method below, this can be a quite inexpensive device to buy and maintain.

Ultrasonic and constant temperature anemometers may be accurate enough for most purposes; but laser Doppler anemometers offer extremely tight accuracy. A laser anemometer uses two laser beams; one that travels through a sealed and clean pathway, and one that travels through exposed air. The beam that travels through the exposed air encounters dust particles that are borne along at the speed of the wind at the point. The laser bounces off those dust particles, and measures by Doppler shift the speed at which the particle has been traveling. The Doppler shift is compared to what is measured for the beam traveling through the sealed tube and a relative measurement is made.

It would appear from these descriptions that anemometers always need to be large and permanent installations; as it happens though, small and inexpensive handheld versions with digital displays exist for use by field researchers and trainer pilots. The most striking feature of these is the way they recognizably use nothing other than the same mechanics and structures of the professional devices, only miniaturized for handheld use.

The Travelers’ Temperature Predicaments (2)

Temperature measurement is very important to a whole range of areas and activities: science, scientific research, manufacturing, medicine and travel. Many European, Asian and African businessmen and tourists often travel to the USA and UK. These countries have not adopted the use of the modern metric system of measurement i.e. the SI system.

The accepted base SI unit of temperature is the Kelvin. A change of 1K is the same as 1 degree Celsius. As the degree Celsius is a convenient, easy to grasp in every – day – life metric unit, therefore both units are used in parallel. The Kelvin is used by scientists and engineers and the degree Celsius by everybody else worldwide. There are however, two prominent exceptions: the USA and UK who commonly use the Fahrenheit scale.

Daniel, Gabriel Fahrenheit, a German physicist was born in 1686 in Gdansk, Poland. The concept of the thermometer for measuring temperature changes is credited to Galileo. Fahrenheit is known for inventing the alcohol and mercury thermometers. His temperature scale is based on affixing 32º for melting point of ice and 212º for the boiling point of water under normal atmospheric pressure. The interval between two affixed points is being divided into 180 equal parts (the degrees Fahrenheit). The Fahrenheit scale was generally in use by English speaking countries up until 1970.
Travelers to the USA and UK are often faced with the problem of how to efficiently convert the temperature in the degree Fahrenheit to the temperature expressed in the degrees Celsius without making a mistake and with a sufficient approximation.

The conversion formula “Fahrenheit to Celsius” is:

ºC = 5/9 (ºF – 32º); read:

“In order to express the temperature in the degrees Celsius, I need to divide 5 by 9 and the result multiply by the temperature in Fahrenheit lowered by 32º”.

Quite awkward, isn’t it?

A much simpler way to remember and easier method to do mentally is to memorise the four following steps:

ºF→→→ºC : “Subtract 32, divide by 2, add 10% ( or 1/10) of the result and add 1% of the total”.

Let us see how it works:

E.g. 1: 98 ºF (your normal body temperature) →→→66 →→→33 →→→36.3 →→→36.7 ºC (rounded off to one decimal place).

E.g. 2: 102 ºF (your possible body temperature) →→→70→→→35→→→38.5→→→38.9 ºC

(High, pay a visit to the doctor!).

E.g. 3: 68 ºF (pleasant, refreshing outdoor temperature)→→→36→→→18→→→19.8→→→20 ºC

If you in a good mood, hum these four steps before the travel: “su-di-a-a”, “su-di-a-a”, “su-di-a-a”…!

Have a nice trip and keep warm!

Wacek

PS.: Have you read my former article: “The Travelers Temperature Tips”?

If so, you will be able to find the answer to the following puzzle:

FORGETFULNESS

A student solving a problem on transfer of heat found a correct temperature change. However, he presented the answer without a unit. As it turned out, it did not matter whether he gave the temperature in the degrees Fahrenheit or the degrees Celsius. The answer remained the same. What temperature was it?

Successful Incentive Travel Begins With Good Planning

Developing a successful incentive travel reward takes a little pre-planning and work to ensure it generates desired results. A company must first determine what business goals are to be achieved through the use of this type of program. Having a basis of what will be accomplished makes it easier to set reachable milestones and select a motivating destination. This basis also allows a company to choose an itinerary that is capable of promoting the purpose of the program. Travel packages are typically implemented to boost sales, amplify morale, promote a product, retain employees, or as a method for creating a loyal customer base. One program does not typically solve every experienced difficulty within an organization. Needs should be organized in a list fashion in order to tackle the most urgent ones at first. An incentive could target customers, employees, or a business area such as sales and should be used as a driver to reach the desired results.

Incentive Travel: Tips for Setting Reward Objectives

The set objectives should be a first priority when beginning to form an incentive travel plan. Trip packages are more capable of supplying the anticipated outcome when the necessary accomplishments are known and understood. Taking a problem and turning it into a goal makes a good approach to resolving organizational issues. An issue can include these among other scenarios:

Sales

Safety

Service

Teamwork

Morale

Attendance

The characteristics of possible realistic aims will guide the way as a company chooses what will be accomplished by a motivational program. A business or department performing this planning must remain focused on what is to be accomplished and create simple aims with a precise purpose. All objectives being achieved with an award program have to be related in order to for participants to understand what must be done. Unrelated goals should be achieved in separate packages to ensure a successful incentive travel plan. An ambiguous goal can seem like a great idea; however, it will only be a success when the objective is achievable. A planned set of objectives must be:

Realistic

Reachable

Measurable

Timed Appropriately

In Line With Company Goals

The path to an award has to be measurable in order to make the process fair and encourage continued participation. Incentive travel awards create an environment full of healthy competition and measurable progress is the only way to make this productivity fostering environment possible. Awards used on the customer side of business must also be measurable to make certain consumers know what they have to do to receive the offered incentive. Setting a high sale goal or a set number of new customer sign on during a slow time of business is not fair to participants. The purpose must match the time of the year and what is realistically possible for a program to be effective. Additionally, all chosen goals should fall in line with organizational aims and stay true to set policies. Taking the time to properly decide these elements before choosing a destination or promoting activities will greatly increase the success of this motivational endeavor.