Psychrometric Diagram Calculator

Air Pressure (hPa)

Condition Visibility

Outside

Above Screen

Inside

Plant

Temperature (°C)

Relative Humidity (%)

Temperature (°C)

Relative Humidity (%)

Temperature (°C)

Relative Humidity (%)

Temperature (°C)

Relative Humidity (%)

All Conditions Comparison

Conditions:

Outside

Above Screen

Inside

Plant

Chart Lines:

Relative Humidity

Enthalpy (kJ/kg)

Saturation Curve

Psychrometric Calculations & Formulas

Input Parameters

Dry Bulb Temperature (T)

The temperature of air measured by a standard thermometer.

Unit: °C

Relative Humidity (RH)

The ratio of actual vapor pressure to saturated vapor pressure at the same temperature.

Unit: %

Air Pressure (P)

Atmospheric pressure affecting psychrometric calculations.

Unit: hPa (hectopascals)

Vapor Pressure Calculations

Saturated Vapor Pressure (VPsat)

Maximum vapor pressure at a given temperature using Magnus formula.

VPsat = 0.61078 × e^(17.27×T / (T+237.3))

Unit: kPa

Vapor Pressure (VP)

Actual vapor pressure in the air.

VP = VPsat × (RH / 100)

Unit: kPa

Vapor Pressure Deficit (VPD)

Difference between saturated and actual vapor pressure.

VPD = VPsat - VP

Unit: kPa

Humidity Calculations

Absolute Humidity (AH)

Mass of water vapor per unit volume of air.

AH = (VP × 1,000,000) / (461.52 × (T + 273.15))

Unit: g/m³

Humidity Deficit (HD)

Difference between saturated and actual absolute humidity.

HD = AHsat - AH

Unit: g/m³

Dewpoint Temperature

Temperature at which air becomes saturated (100% RH).

Dewpoint = (237.3 × ln(VP/0.61078)) / (17.27 - ln(VP/0.61078))

Unit: °C

Energy Calculation

Enthalpy (h)

Total heat content of moist air per unit mass of dry air.

h = 1.006 × T + (AH/1000) × (2501 + 1.86 × T)

Unit: kJ/kg

Where 1.006 is specific heat of dry air, 2501 is latent heat of vaporization, and 1.86 is specific heat of water vapor.

Chart Elements

Saturation Curve (100% RH)

Shows maximum moisture capacity at each temperature.

Constant RH Lines

Lines of equal relative humidity from 10% to 90%.

Constant Enthalpy Lines

Lines of equal total heat content from 20 to 100 kJ/kg.

Condition Points

Plotted points showing current state of each monitored condition.

Applications

Outside Conditions

Environmental monitoring for weather and climate assessment.

Above Screen

Monitoring conditions above plant canopy in greenhouse operations.

Inside Conditions

Indoor air quality and comfort assessment.

Plant Conditions

Direct monitoring at plant level for optimal growing conditions.