Operating Principle:

Extech thermocouples operate on the Seebeck effect, generating a voltage when two different metals at different temperatures are joined, enabling precise temperature measurement based on the current produced.

• Advantage: It can measure small differences in temperature and is fast responding.

• Disadvantage: The fragile wires are easily subject to corrosion, leading to drift.

• Uncertainty: The presence of a slight non-linearity between the thermoelectric voltage and temperature requiring frequent calibration.

Operating Principle: 

An IR thermometer works by detecting infrared radiation emitted from an object, converting it into an electrical signal, and then calculating the temperature based on the intensity of the radiation. The variable measured by the instrument is temperature, providing non-contact temperature readings of the object being measured.

• Advantage: It is a non-contact measurement, making it easily accessible.

• Disadvantage: It is sensitive to surface emissivity, causing inaccurate temperature measurements of reflective surfaces.

• Uncertainty: The measurements are subject to exposure error caused by ambient temperature, wind, humidity, or dust in the air.

Operating Principle:

A mercury thermometer operates on the principle of thermal expansion, where the volume of mercury expands or contracts with temperature changes, causing it to rise or fall in a calibrated glass tube. The variable measured by the instrument is temperature, with the height of the mercury column indicating the temperature of the environment being measured.

• Advantage: They produce highly accurate readings within the range of -30 C to 250 C

• Disadvantage: The mercury is highly toxic to the environment. 

• Limitation: It has a slow response time due to the mercury's high thermal mass.