THERMAL SENSORS

Thermocouple

It measures temperature differences between two locations using two dissimilar conductors.

Seebeck Effect

It describes how a temperature difference between two dissimilar electrical conductors produces a voltage.

Law of Homogenous Circuits

This law states that current cannot be sustained in a circuit of a single homogeneous metal.

Law of Intermediate Metals

This law states that if you introduce a third metal into your circuit, it won't change the total voltage as long as both ends of that third metal are at the same temperature.

Law of Intermediate Temperatures

This law states that the voltage produced between two temperatures (T1 and T3) is simply the sum of voltage between T1 to T2 and T2 to T3.

5.507 mV

What will be the output voltage of a J type thermocouple, if the measured temperature is 100 degrees celcius?

Resistive Temperature Detector

It is a temperature sensitive resistor and a positive temperature coefficient device.

Wire-wound

A type of RTD that is manufactured by winding a small diameter of wire into a coil on a suitable winding

Thin-film

A type of RTD that consists of a very thin layer of the base metal, which is deposited onto a ceramic substrate and then laser trimmed to the desired resistance value.

Thermistor

A type of resistor whose resistance varies significantly with temperature.

Steinhart-Hart Equation

This equation describes the resistance change of a thermistor as related to its temperature.

Positive Temperature Coefficient

A type of thermistor when temperature increases, resistance increases.

Negative Temperature Coefficient

A type of thermistor when temperature increases, resistance decreases.

Solid-State Temperature Sensors

A type of temperature sensor that uses the PN junction of a diode to measure temperature

Bandgap Voltage Reference

It is a circuit used in ICs to provide a constant, reliable voltage reference.

Pyrometer

A device that measures temperature where the surface to be measured cannot be brought into contact.

Optical Pyrometer

It is device which allows contactless temperature measuring by using the incandescence color.

dark

The lamp filament is initially cooler than the target and appears ___ before it.

bright

The lamp filament is initially hotter than the target and appears ___ before it.

blends/matches

The lamp current is adjusted until lamp temperature equals that of the target. The filament ___ into the glowing background of the target.

Infrared Pyrometer

A pyrometer that collects infrared energy and focuses it onto the detector where it is converted into electrical energy.

Stefan-Boltzmann Law

A pyrometer operates based on what law?

Hygrometer

An instrument used to measure the amount of water vapor.

Relative Humidity

(actual vapor pressure / saturation vapor pressure ) x 100%

It is a measure of how moist the air is.

What is its formula?

Metal-Paper Coil

A type of hygrometer that uses a coil made of metal and paper bounded together.

it absorbs and expands

In a metal-paper coil, what happents to the paper side when humidity increases?

Hair Tension Hygrometer

A type of hygrometer when humidity increases, hair absorbs moisture and lengthens.

Chilled Mirror Dew Point Hygrometer

A type of hygrometer that measures the exact temperature where vapor reaches saturation level.

Psychrometer

A type of hygrometer that consist of two thermometers, one which is dry and one which is kept moist.

Capacitive Humidity Sensor

A type of hygrometer that measures the effect of humidity on the dielectric constant of a polymer or metal oxide material.

Resistive Humidity Sensor

A type of hygrometer that measures the change in resistance of a material due to humidity.

Thermal Conductivity Sensor

A type of hygrometer that measure the absolute humidity rather than relative humidity.

It also measures the change in thermal conductivity of air due to humidity.

Gravimetric Hygrometer

A type of hygrometer measures the mass of an air sample compared to an equal volume of dry air.