thermal indicies

Dry-bulb temperature

Ambient air temperature measured with a standard thermometer

Ambient temperature

The surrounding environmental air temperature

Sensible heat

Heat that causes a temperature change without a phase change

Standard thermometer

Instrument used to measure dry-bulb temperature

Thermocouple

Temperature sensor made of two metals producing voltage when heated

Thermistor

Temperature-sensitive resistor used for temperature measurement

Wet-bulb temperature

Temperature measured by a thermometer wrapped in a wet cloth

Evaporative cooling

Cooling caused by evaporation removing heat

Wet-bulb vs dry-bulb

Wet-bulb temperature is usually lower than dry-bulb

Wet-bulb at 100% RH

Wet-bulb equals dry-bulb because evaporation cannot occur

Psychrometer

Instrument with wet and dry thermometers used to measure humidity

Relative humidity

Percentage of water vapor in the air relative to its maximum capacity

50% relative humidity

Air holds half the moisture it could contain

Hair hygrometer

Instrument measuring humidity using hair expansion

Electronic humidity sensor

Device that measures humidity electronically

Chill-mirror hygrometer

Device detecting humidity through condensation on a cooled mirror

Surface temperature

Temperature of animal body surface or surrounding surfaces

Infrared thermometer

Non-contact device measuring surface temperature

Contact temperature sensors

Thermocouples or thermistors measuring surface temperature

Dew point temperature

Temperature at which air becomes saturated and condensation forms

Saturation temperature

Temperature where air holds maximum moisture

Condensation

Water vapor turning into liquid water

Dry-bulb vs wet-bulb relationship

Wet-bulb temperature is always less than or equal to dry-bulb temperature

Evaporation potential indicator

Difference between dry-bulb and wet-bulb temperatures

Large DB-WB difference

Indicates dry air and strong evaporation potential

Small DB-WB difference

Indicates humid air with limited evaporation

Temperature vs relative humidity

Warm air holds more water vapor than cold air

Cooling air effect

Relative humidity increases if water content stays constant

Dew point vs humidity

Higher dew point indicates more moisture in air

Air reaching dew point

Relative humidity becomes 100%

Dry-bulb measurement tools

Thermometer, thermistor, thermocouple

Wet-bulb measurement tool

Psychrometer

Relative humidity measurement tools

Psychrometer or hygrometer

Surface temperature measurement tools

Thermocouple or infrared thermometer

Dew point measurement tools

Psychrometric calculations or chill-mirror hygrometer