define
calibration of thermometer
Answers
Answer:
Temperature calibration refers to the calibrationof any device used in a system that measures temperature. Most importantly, this usually means the temperature sensor, itself, which is typically a platinum resistance thermometer(PRT or PT-100), thermistor, or thermocouple.
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Answer:
Revision 3.1
Laboratory Exercise: Calibration of a Thermometer
In this exercise we will calibrate a stem-type thermometer and then use it to correctly measure
the Air temperature of the laboratory.
One of the most common types of laboratory thermometers is the liquid-expansion thermometer.
In this type of thermometer, an expansion liquid, usually Mercury or Alcohol, fills a glass bulb
attached to a long stem with a uniformly bored expansion column.
When heated, the liquid expands up the bore until the bulb reaches
thermal equilibrium with the material whose temperature is being
measured. The expansion of the liquid is such that the height it reaches
in the stem is linear with temperature. These thermometers are typically
marked with equal spacings along the stem. They are then calibrated at
two different "fixed point" temperatures. Alcohol thermometers are of
lower accuracy than Mercury thermometers, but are more commonly
used in the chemistry laboratory because Mercury is toxic and difficult
to clean-up in the case of breakage. The lower accuracy of an Alcohol
thermometer is due to two reasons: (1) Alcohol is more volatile than
Mercury and so will vaporize into the space above the liquid in the
stem; and (2) Alcohol tends to “wet” the sides of the stem’s bore such
that when the temperature drops, part of the liquid remains along the
wall of the bore.
As with any measuring device, the accuracy of the device can only be
judge by calibration of the device. Calibration is such that a
measurement is performed whose result is well known. The instrument
is then adjusted such that its reading gives this result. Or, a correction
factor is determined such that subsequent readings can be corrected for
the known instrument error. For a stem thermometer, because the
markings along the stem cannot be adjusted, a Correction Curve is
prepared such that thermometer readings can be converted to accurate
temperatures. Known temperature baths for calibration can be
generated using the Ice Point and the Boiling Point of Water. These
temperature baths are called "fixed points" because of their use aRevision 3.1
Laboratory Exercise: Calibration of a Thermometer
In this exercise we will calibrate a stem-type thermometer and then use it to correctly measure
the Air temperature of the laboratory.
One of the most common types of laboratory thermometers is the liquid-expansion thermometer.
In this type of thermometer, an expansion liquid, usually Mercury or Alcohol, fills a glass bulb
attached to a long stem with a uniformly bored expansion column.
When heated, the liquid expands up the bore until the bulb reaches
thermal equilibrium with the material whose temperature is being
measured. The expansion of the liquid is such that the height it reaches
in the stem is linear with temperature. These thermometers are typically
marked with equal spacings along the stem. They are then calibrated at
two different "fixed point" temperatures. Alcohol thermometers are of
lower accuracy than Mercury thermometers, but are more commonly
used in the chemistry laboratory because Mercury is toxic and difficult
to clean-up in the case of breakage. The lower accuracy of an Alcohol
thermometer is due to two reasons: (1) Alcohol is more volatile than
Mercury and so will vaporize into the space above the liquid in the
stem; and (2) Alcohol tends to “wet” the sides of the stem’s bore such
that when the temperature drops, part of the liquid remains along the
wall of the bore.
As with any measuring device, the accuracy of the device can only be
judge by calibration of the device. Calibration is such that a
measurement is performed whose result is well known. The instrument
is then adjusted such that its reading gives this result. Or, a correction
factor is determined such that subsequent readings can be corrected for
the known instrument error. For a stem thermometer, because the
markings along the stem cannot be adjusted, a Correction Curve is
prepared such that thermometer readings can be converted to accurate
temperatures. Known temperature baths for calibration can be
generated using the Ice Point and the Boiling Point of Water. These
temperature baths are called "fixed points" because of their use a
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