Weather Weather InstrumentsInstruments

Unit 11 - Day 1Notes

Have a red book open to page 60.

ThermometerThermometer

Thermometers Thermometers measure air measure air temperatures. temperatures. Thermometers Thermometers work because work because matter expands matter expands when heated. when heated. Most Most thermometers are thermometers are closed glass tubes closed glass tubes containing liquids containing liquids such as alcohol.such as alcohol.

BarometerBarometer

A barometer A barometer measures air measures air pressure.pressure.

There are There are two types of two types of Barometers: Barometers: Mercury Mercury Barometer Barometer and Aneroid and Aneroid Barometer.Barometer.

A Mercury A Mercury Barometer Barometer consists of a glass consists of a glass tube inserted into tube inserted into a dish of mercury a dish of mercury or colored or colored denatured alcohol.denatured alcohol.

*(If you build your *(If you build your own, don’t use own, don’t use mercury) mercury)

The surrounding The surrounding air presses down air presses down on the mercury in on the mercury in the dish and forces the dish and forces some of the some of the mercury up into mercury up into the tube. The the tube. The height to which the height to which the mercury rises in mercury rises in the tube is directly the tube is directly proportional to the proportional to the atmospheric atmospheric pressure.pressure.

PsychrometerPsychrometer

A psychrometer A psychrometer measures the measures the humidity of the humidity of the air. One of the air. One of the two two thermometers thermometers has a wick has a wick (cloth cover) (cloth cover) which is dipped which is dipped in distilled in distilled water.water.

Evaporation of Evaporation of water from the water from the wick on the wet wick on the wet bulb thermometer bulb thermometer leads to cooling. leads to cooling.

Using a Relative Using a Relative Humidity Table, Humidity Table, the temperature the temperature difference between difference between the two the two thermometers thermometers gives the relative gives the relative humidity of the air humidity of the air (in percent).(in percent).

This is an This is an example example of the of the type of type of table you table you would would use. Your use. Your book book might might also also have an have an example.example.

One such One such psychrometer psychrometer is a is a Sling Sling Psychrometer.Psychrometer.

Measurements are taken by whirling the psychrometer with the handle.

AnemometerAnemometer

An Anemometer An Anemometer measures the measures the wind speed. The wind speed. The cups catch the cups catch the winds, turning a winds, turning a dial attached to dial attached to the instrument.the instrument.

Think you could Think you could build one of build one of these?these?

Time for a little Time for a little review!review!

1.1. If I wanted to If I wanted to find out if the find out if the pressure was pressure was rising, I’d use rising, I’d use which of the which of the following?following?

A)A) ThermometerThermometerB)B) BarometerBarometerC)C) PsychrometerPsychrometerD)D) Wind VaneWind VaneE)E) Rain GaugeRain GaugeF)F) AnemometerAnemometer

2.This is used 2.This is used to determine to determine the relative the relative humidity.humidity.

A)A) ThermometerThermometerB)B) BarometerBarometerC)C) PsychrometerPsychrometerD)D) Wind VaneWind VaneE)E) Rain GaugeRain GaugeF)F) AnemometerAnemometer

3. Can help you 3. Can help you find out the find out the wind speed.wind speed.

A)A) ThermometerThermometerB)B) BarometerBarometerC)C) PsychrometerPsychrometerD)D) Wind VaneWind VaneE)E) Rain GaugeRain GaugeF)F) AnemometerAnemometer

4. If I wanted to 4. If I wanted to know the know the difference difference between the between the temperature temperature inside and inside and outside of the outside of the classroom.classroom.

A)A) ThermometerThermometerB)B) BarometerBarometerC)C) PsychrometerPsychrometerD)D) Wind VaneWind VaneE)E) Rain GaugeRain GaugeF)F) AnemometerAnemometer

How did you do? Here How did you do? Here are the correct are the correct

answersanswers1. B. Barometer1. B. Barometer

2. C. Psychrometer2. C. Psychrometer

3. F. Anemometer3. F. Anemometer

4. A. Thermometer4. A. Thermometer