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Saturation Conditions
Calculated water vapor pressure higher than saturation vapor pressure.
Increase sample temperature or reduce input humidity.
Calculated water vapor pressure higher than total pressure.
Increase sample pressure or reduce input humidity.
Calculated water vapor or saturation vapor pressure is negative.
Input parameters out of range.
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While every effort has been made to ensure the formulae used in this calculator are correct, this free software service is provided 'as is' and without warranty or guarantee to the extent of the applicable law.
PST Michell Industrial Dew Point Calculator
What is dew point?
Dew point is the temperature gas gets saturated with water which then results in the formation of dew or fog. Our Michell industrial dew-point calculator facilitates swift and effortless humidity calculations and parameter conversions for engineers. It is designed to be used as a standalone tool or combined with a hygrometer.
The dew-point calculator can calculate humidity values at different pressures, calculate parameters unavailable on a particular instrument, or convert previously measured data to alternative parameters.
Users can calculate or convert multiple parameters, including dew-point temperature, ppmv to dp, frost-point temperature, relative humidity, absolute humidity, ppm (parts per million ), ppm to mg/m3, mixing ratio, wet bulb temperature, water vapor pressure & saturation vapor pressure, and enthalpy.
The dew-point calculator uses the Sonntag formula for water vapor pressure as seen in the British Standard 1339:1, 3.2.2. Users can customize the settings to change which parameters are shown and alter the order to ensure complete ease of use.
Alternatively, you can use our pressure dew point conversion chart over ice and water. The tables include conversions using the Sontag and Wexler methods.
How to use the humidity calculator
Watch the quick video below for a demonstration of how to use the PST Michell Industrial Humidity and Dew-Point Calculator.
FAQ
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What formula is the dewpoint calculator built on?
The PST Michell humidity calculator uses the Sonntag formula for water vapor pressure. It can be found in British Standard 1339:1, 3.2.2.
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What are the uncertainties used in the Sonntag equation?
The humidity calculator is intended for use within the range of -100°C to +100°C dew point (at atmospheric pressure). Calculations outside this range may yield unexpected results. It's also worth noting that calculations under atmospheric pressure may produce unexpected outcomes due to the distinct behavior of water vapor in vacuum conditions.
The uncertainties (coverage factor approximately k=2) of the polynomials used in the Sonntag equation are as follows:
Less than 0.01% of the vapor pressure value for water between 0°C and 100°C.
Less than 0.6% of the vapor pressure value for supercooled water between 0°C and -50°C.
Less than 1.0% of the vapor pressure value for ice between 0°C and -100°C.
This translates to dew-point uncertainties as follows:
±0.014°C to ±0.0029°C for water between 0°C and 100°C.
±0.07°C to ±0.053°C for supercooled water between 0°C and -50°C.
±0.12°C to ±0.049°C for ice between 0°C and -100°C.
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How do we calculate water vapor pressure and saturation water vapor pressure?
In Michell chilled mirror products, both water vapor pressure (WVP) and saturation water vapor pressure (SWVP) are calculated using the Sonntag vapor pressure formula. This formula comes in two variations: the "over water" formula and the "over ice" formula. Generally, the "over water" formula is chosen when the temperature (or dew-point temperature) is above 0 °C, while the "over ice" formula is used for temperatures below 0 °C.
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Related Articles
At PST, we diligently stay abreast of the latest industry trends, ensuring that we remain at the forefront of knowledge. Our commitment extends to educating our esteemed visitors on the best practices in the industry. You can access our most recent articles on our blog page or subscribe to our monthly newsletter.
Dew Point Definition and How to Measure It For Industries?
Unlike relative humidity or dew point, moisture content doesn’t change with pressure or temperature: it’s a measure of the actual molecules of water in the gas.
Humidity Academy Theory 3 – Humidity and Vapor Pressure
The partial pressure of water vapor is a key metric found as a component in the formulas that define all other humidity parameters.
Humidity Academy Theory 4 – Definitions of Humidity: Vapor Concentration
The vapor concentration or absolute humidity of a mixture of water vapor and dry air is defined as the ratio of the mass of water vapor Mw to the volume V occupied by the mixture.
How a Michell Chilled Mirror Hygrometer Measures Relative Humidity
This blog post looks at when a chilled mirror hygrometer is appropriate and how the calculations are made using Michell Optidew chilled mirror hygrometers.
How to Calculate Pressure Dew Points (PDP) Accurately
Unlike moisture content which is a fixed value no matter the temperature or the pressure, the dew-point temperature of a gas is relative to the pressure.
Pressure-Dew-Point chart
We have created a look-up pressure-dew-point chart that you can download and keep as a handy reference. The tables include conversions using the Sontag and Wexler methods.