PROF. PIERO MAMMINO

MAXIMUM AND MINIMUM THERMOMETERS (SIX’S THERMOMETER)

HOW THEY ARE MADE U-shaped glass capillary tube Two separate temperature readings Bulbs at the top of each arm On the right bulb there is alcohol On the left bulb there is vacuum Two steel markers moved by the mercury movements Steel markers moved by a magnet to reset the thermometer

HOW TO USE THEM Mercury expands and contracts as temperatures rise and fall; Used to measure the hottest and coldest temperature in a period of time; The maximum reading is recorded at the bottom of the marker in the right tube; The minimum temperature is recorded at the bottom of the marker in the left tube; The current temperature is read on both sides WHERE TO USE THEM No direct sunlight; No source of heat; Bulb 1.25 meters from the ground (not influenced by the soil temperature); Away from buildings (no radiate heat)

WHY TO USE THEM Daily range of temperature (max temperature minus min temperature for one day); Mean daily temperature (max temperature plus min temperature divided by two) Mean monthly temperature (average daily temperature divided by the numbers of days) Annual range (temperature of the warmest month minus temperature of the coldest) Mean annual temperature (total of the monthly means divided by 12)

25° C

30° C

10° C

12°

2°

3°

COMPARING TEMPERATURE AND RAINFALL

HYGROMETER (or wet and dry bulb thermometer)

The HYGROMETER is used to measure the relative humidity in the air

HOW THEY ARE MADE Made up of two thermometers A dry thermometer measures the temperature of the air The wet bulb thermometer is covered by an absorbent wick ending in a container of distilled water The wet bulb thermometer measures the temperature of the air if there was 100% humidity (absolute humidity) If the humidity of the air is 100% the readings on both thermometers will be the same

HOW TO USE THEM Record the temperatures of both the thermometers Calculate the difference between the two readings Look up the results in a relative humidity table

Conversion table

12° C

20° C

20 – 12 = 8° C

Dry

bu

lb r

ead

ing

Difference between the two readings