SM0486
at which you wish the thermometers calibrated.
h. Although the "wells" (openings into which the thermometers are placed for
calibration) are not shown in figure 10, they are located in such a position in the
calibrator that they can be completely enclosed by a synthetic non-flammable oil
which is used in the heat transfer process.
It doesn't matter whether you are
calibrating thermometer scales at the freezing point of water; the calibrator scale
must first be calibrated with the standard thermometer which is your reference.
You should realize that your greatest concern over your thermometer calibrator is
with its stability and repeatability, not its accuracy.
i. Let us check to see if any of the laws of physics listed or principles
based on those laws are involved in the use of the thermometer calibrator.
The
first law concerns heat and kinetic energy.
Heat is generated by electrical
currents. These currents consist of electrons which do move and do possess kinetic
energy. Therefore, you can see that the first law listed has an application. The
second law listed concerns the transfer of heat. When the calibrator is used for
thermometer calibration, a synthetic non-flammable oil was mentioned.
One of the
purposes for using this oil is its heat conducting capabilities.
So you can see
that the second law has an application in the use of the thermometer calibrator.
6.
RELATED HEAT SENSING AND MEASURING INSTRUMENTS
You should know the thermal measurement principles and methods applied in the
operation and calibration of heat measuring devices such as thermocouples and
a. Thermocouples.
Remember that when two unlike metals, such as copper and
iron, are connected as shown in figure 11, the junction of the metals can be used
as a part of a temperature measuring device. If heat is applied to the left-hand
joint (A) shown in figure 11 while the right-hand joint (B) remains at room
temperature (cold), a voltage is generated which causes the galvanometer to
deflect.
The amount of deflection is proportional to the difference in the
temperatures at A and B. This device is known as a thermocouple.
Figure 11.
A simple thermocouple.
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