Experiment A: Temperature Measurement Methods

Objective:

To demonstrate the application of temperature scales and fixed points using mercury-glass

thermometer, bimetallic thermometer, thermocouple, resistance temperature detector, and

thermistor and vapor pressure thermometer.

Experiment Procedures:

1. Fill the water heater with clean water and connect the power cord.

2. Half fill the vacuum flask with a mixture of crushed ice and pure water (the ice being

made from pure water and crushed into fine particles).

3. Ambient air temperature measurement:

Take out the mercury-glass thermometer, close inspection will reveal a column of mercury

protrude from the bulb. Temperature measurement is achieved by relating the length of this

column to an engraved scale on the glass. Read the temperature indicated by the column at

ambient air temperature.

Take out the mercury in bi-metal thermometer, close inspection will reveal a metal rod at the

end of the indicator. Temperature measurement is achieved by transferring heat to the metal

rod.

Take out a Type K thermocouple. Connect the blue and yellow plugs to the corresponding

sockets of the Type K thermocouple temperature indicator. Place the thermocouple on the

baseboard and allow the readings to stabilize at the ambient air temperature. Read the

temperature indicated on the temperature indicator.

Take out a resistance temperature detector (RTD). Connect the RTD plug to the

corresponding sockets of the RTD indicator. Place the RTD on the baseboard and allow the

readings to stabilize at the ambient air temperature. Read the temperature indicated on the

RTD temperature indicator.

Take out a thermistor. Connect the thermistor plugs to the corresponding sockets of the

thermistor indicator. Place the thermistor on the baseboard and allow the readings to

stabilize at the ambient air temperature. Read the temperature indicated on the thermistor

indicator.

Take out the vapor pressure thermometer. Place the vapor pressure thermometer on the

baseboard and allow the readings to stabilize at the ambient air temperature. Read the

temperature indicated on the indicator

4. Ice-point temperature measurement

Insert the bulb of the thermometer into the water-ice mixture; stir gently to ensure intimate

contact with the mixture. Observe the reading on the thermometer.

Insert the metal rod of the bi-metal thermometer into the water-ice mixture; stir gently to

ensure intimate contact with the mixture. Observe the reading on the bimetallic

temperature indicator.

Insert the thermocouple probe into the water-ice mixture; stir gently to ensure intimate

contact with the mixture. Observe the reading on the thermocouple temperature indicator.

Insert the RTD probe into the water-ice mixture; stir gently to ensure intimate contact with

the mixture. Observe the reading on the RTD temperature indicator.

Insert the thermistor probe into the water-ice mixture; stir gently to ensure intimate contact

with the mixture. Observe the reading on the thermistor temperature indicator.

Insert the metal rod of the vapor pressure indicator into the water- ice mixture; stir gently

to ensure intimate contact with the mixture. Observe the reading on the indicator.

5. Boiling-point temperature measurement Insert the bulb of the thermometer into boiling water. Observe the reading on the

thermometer.

Insert the metal rod of the bimetallic indicator into boiling water. Observe the reading on

the bimetallic indicator.

Insert the thermocouple probe into boiling water. Observe the reading on the temperature

indicator.

Insert the RTD probe into boiling water. Observe the reading on the resistance indicator.

Insert the thermistor probe into boiling water. Observe the reading on the thermistor

indicator.

Insert the metal rod of the vapor pressure indicator into boiling water.

Observe the reading on the thermometer.

Repeat the readings in ice and boiling water and observe that the readings are consistently

0C and 100C respectively.

Note:

The boiling point of water occurs at 100C for standard atmosphere pressure only(760mmHg).

At lower atmospheric pressure, boiling will occur at lower temperature and, conversely, at

higher atmospheric pressure, boiling will occur at high temperature. For example, a rise in

atmosphere of 27 mmHg above the standard pressure will result in a rise of 1C in the boiling

water point of water. Where boiling occurs at a temperature other than 100C, a barometer

should be consulted to confirm the deviation.

Pure water must be used where accurate calibration is required, paying attention to

atmospheric pressure at the time of calibration. On completion of the experiment, switch off

the water heater.

Observations:

Apparatus Ambient (C) Ice Point (C) Boiling Point (C)

Glass Thermometer (10C to 110C)

Glass Thermometer (5C to 350C)

Bimetal Thermometer

RTD

Thermistor

Type K Thermocouple

Vapor Pressure Thermometer