Temperatures and the Thermometer

Temperature is the measurement of the relative 'hotness" or "coldness" of an object. Temperature is related to heat, but the two are not synonymous terms. Heat is an energy state, and it is measured in work units. Temperature is a measure of the relative heat intensity of an object.

The substance used as a basis for measuring temperature is water. The comparison is made by means of a scale, e.g., centigrade, Fahrenheit, or Kelvin. On each of these scales there are two fixed points, the melting point of ice and the boiling point of water.

The German physicist Gabriel Daniel Fahrenheit (1686-1736) devised one of the earliest scales, with the freezing point at 32 degrees and the boiling point at 212 degrees. The centigrade, or Celsius, scale, was invented by the Swedish astronomer Anders Celsius (1701-44). Used throughout most of the world, it assigns a value of 0 degrees to the freezing point, and 100 degrees to the boiling point. The Kelvin scale is used in scientific work and was invented by the British mathematician William Thomas, 1st Baron Kelvin ((1824-1907). Absolute zero is at -273.16 degrees and the degree intervals are identical to those measured on the centigrade scale.

The formula to convert Celsius to Fahrenheit is F = (9/5C) + 32, or simplified, F = (1.8C) + 32.

The formula to convert Fahrenheit to Celsius is C = 5/9(F -32). The first instruments which we would recognize as thermometers were made in Florence in the 1650s. Before that there had been instruments which would give a rough idea of temperature changes, using the expansion of air as it was heated to drive a column of water up a tube. But these instruments, known as thermoscopes, were open to the air and were therefore affected by changes in barometric pressure as well as changes in temperature. This made them hard to interpret.

The sealed thermometer, in which a column of liquid expands as it is heated and indicates temperature by the movement of its leading edge up a graduated scale, was invented by Ferdinand II, Grand Duke of Tuscany, in about 1654. The liquid used was alcohol, and the instrument consisted of a glass bulb to which a fine tube was attached.

Most contemporary thermometers have used mercury to indicate temperature, because its coefficient of expansion is nearly constant. However, mercury is a pollute and the half-gram of mercury in a thermometer is enough to pollute 5 million gallons of water. Hence, lately people are encouraged to buy non-mercury thermometers.

Automobile Instruments of Measurement

Several important instruments of measurements are used in the operation of the automobile:

1. The speedometer, to measure the speed of the car.

2. The odometer, to measure the distance driven.

3. The temperature gauge. Watch this one very carefully or an overheated engine can be quite costly. Note: take a look at the old motometer on display. A motometer is an old type of thermometer situated on top of a radiator.

4. Oil pressure gauge. No oil pressure will usually result in your needing a new engine.

5. Ammeter, to measure amps. If the generator or alternator is not working, you should have some jumper cables handy.

6. Tire pressure gauge. A necessity in the day of self-serve car stations.

7. Gas gauge, to measure gallons of gasoline. Pay attention to this measurement, even though many cars today will display on the dashboard how many miles to go before a refill is needed.

All in all, measurements play a very important role in both the manufacture and operation of the automobile of today.