Evaporation Time and Humidity Calculation: Can You Calculate Humidity Using Evaporation?


Can You Use Evaporation Times to Calculate Humidity?

Interactive Calculator & In-Depth Guide

Evaporation & Relative Humidity Calculator

This calculator estimates Relative Humidity (RH) based on the time it takes for a specific amount of water to evaporate under controlled conditions. It’s a simplified model, but demonstrates the principle.


Volume of water in milliliters (ml).


The exposed surface area of the water in square centimeters (cm²).


Time taken for the water to evaporate in minutes.


The surrounding air temperature in degrees Celsius (°C).


Standard evaporation rate for 100cm² at 100% RH and 25°C (e.g., 0.05 ml/min/100cm²). This is a crucial calibration factor.



Formula Used:

1. Evaporation Rate (ER): Calculated as `Water Volume / Evaporation Time`. This gives ml/min.
2. Normalized Evaporation Rate (NER): Adjusted for surface area: `ER / Surface Area * 100`. This gives ml/min/100cm².
3. Vapor Pressure Adjustment Factor (VPAF): A simplified factor accounting for temperature’s effect on water’s potential to evaporate. It’s often complex, but here we use a simplified relation where higher temperature increases potential evaporation. `VPAF = (Ambient Temperature / 25)`. This is a very basic approximation.
4. Actual Evaporation Potential (AEP): `Reference Evaporation Rate * NER * VPAF`. This estimates the potential evaporation rate under current conditions compared to the reference.
5. Actual Vapor Pressure (e): We approximate this by relating AEP to saturation vapor pressure. A common simplification is `e = (AEP / Reference Evaporation Rate) * Saturation Vapor Pressure @ Reference Temp`. We’ll use a placeholder for saturation vapor pressure.
6. Saturation Vapor Pressure (E): The maximum vapor pressure the air can hold at a given temperature. This requires complex formulas (like August-Roche-Magnus or Tetens equation). For simplicity, we use a lookup or simplified approximation. For 25°C, it’s approximately 31.69 mbar. We’ll use a basic linear approximation here related to temperature.
7. Relative Humidity (RH): `(Actual Vapor Pressure / Saturation Vapor Pressure) * 100`.
*Note: This model uses significant simplifications, especially for vapor pressure calculations.*

What is Evaporation Time and How Does it Relate to Humidity?

The concept of using evaporation times to gauge humidity, while not a primary scientific method for precise measurement, is rooted in the fundamental physics of water vapor in the air. Relative Humidity (RH) represents the amount of water vapor present in the air compared to the maximum amount it can hold at a specific temperature. When the air is saturated (100% RH), its capacity to hold more water vapor is minimal, and evaporation slows down significantly. Conversely, in dry air (low RH), water evaporates more readily.

Definition: The relationship explored here hinges on the observation that the rate at which water evaporates is inversely proportional to the relative humidity of the surrounding air. The drier the air (lower RH), the faster the evaporation. The more humid the air (higher RH), the slower the evaporation. Evaporation time, therefore, becomes an indirect indicator of the ambient humidity level.

Who should use this concept?

  • Hobbyists & Educators: For demonstrating basic atmospheric science principles in a hands-on way.
  • DIY Enthusiasts: Those interested in understanding environmental conditions without high-tech equipment.
  • Preppers/Survivalists: Gaining a very rough sense of environmental moisture.

Common Misconceptions:

  • Precision: This method is not precise. Professional hygrometers use sophisticated sensors.
  • Consistency: The rate of evaporation is influenced by many factors beyond RH, such as airflow, surface area, water temperature, and atmospheric pressure, making simple time-based calculations prone to error.
  • Direct Measurement: Evaporation time is an *indirect* indicator. It doesn’t directly measure vapor pressure or dew point.

Evaporation Time and Humidity: Formula and Mathematical Explanation

Calculating Relative Humidity (RH) from evaporation time requires us to bridge the gap between a physical process (evaporation rate) and a thermodynamic state (vapor pressure). The core idea is that evaporation is driven by the difference between the vapor pressure of the water surface and the partial pressure of water vapor in the air. The faster the evaporation, the lower the current partial pressure of water vapor relative to the saturation point.

Step-by-Step Derivation:

  1. Calculate Observed Evaporation Rate (ER): This is the fundamental measurement from the experiment.

    ER = Water Volume / Evaporation Time

    Units: milliliters per minute (ml/min)
  2. Normalize Evaporation Rate (NER): Adjust the rate for the surface area exposed, making it comparable across different setups.

    NER = ER / Surface Area * 100

    Units: ml/min per 100 cm²
  3. Estimate Saturation Vapor Pressure (E): This is the maximum water vapor pressure the air can hold at a given temperature. It’s highly temperature-dependent. We’ll use a simplified approximation based on the **August-Roche-Magnus formula** (or a simpler linear interpolation for illustrative purposes). A common value at 25°C is ~31.69 millibars (mbar).

    E ≈ 6.1094 * exp((17.625 * Temperature) / (Temperature + 243.04)) (using Tetens’ equation, common approximation)

    Units: mbar
  4. Estimate Actual Vapor Pressure (e): This is the partial pressure of water vapor currently in the air. This is where the evaporation rate comes in. We assume a relationship where the evaporation rate is proportional to the difference between saturation vapor pressure and actual vapor pressure, adjusted for external factors like airflow. A simplified approach is to relate the NER to a known reference rate under known conditions.

    AEP = Reference Evaporation Rate * (NER / Reference NER) * Temperature_Correction_Factor

    Where `Reference NER` is the normalized rate under reference conditions (e.g., 100% RH). The `Temperature_Correction_Factor` accounts for how temperature affects evaporation potential (higher temp = faster evaporation). A simplified factor could be `(1 + 0.04 * (Ambient Temperature – Reference Temperature))`.

    Then, we relate AEP to vapor pressures. A very rough approximation:

    e ≈ E * (1 - (AEP / (Saturation Rate @ 0% RH))). This is still complex.

    A more practical, albeit simplified, approach used in the calculator links the *observed* NER to a *reference* NER under specific conditions (e.g., known RH and Temp). If we know the reference NER at 100% RH and 25°C, we can infer.

    Let’s refine the calculator’s logic:

    Calculated ER (ml/min) = Water Volume / Evaporation Time

    Calculated NER (ml/min/100cm²) = Calculated ER / Surface Area * 100

    Temperature Factor (TF) = 1 + 0.04 * (Ambient Temperature - 25) (Simple approximation: 4% increase in evaporation per °C above 25°C)

    Estimated Evaporation Potential (EEP) = Calculated NER / TF (This represents the potential evaporation if RH were low)

    Reference Evaporation Potential (REP) = `Reference Evaporation Rate` (This is the NER at 100% RH, 25°C – let’s assume the input `referenceEvaporationRateInput` represents this value at 0% RH, which is a crucial assumption).

    If `referenceEvaporationRateInput` is the rate at 0% RH, then:

    Actual Vapor Pressure (e) ≈ E * (1 - (Calculated NER / (Reference Evaporation Rate / TF))) — this logic is flawed.

    Let’s simplify based on the calculator’s actual implementation:

    Calculated Evaporation Rate (ml/min) = Water Volume / Evaporation Time

    Normalized Evaporation Rate (ml/min/100cm²) = Calculated ER / Surface Area * 100

    Temperature Multiplier (TM) = 1 + 0.04 * (Ambient Temperature - 25)

    Adjusted Normalized Evaporation Rate (ANER) = Normalized Evaporation Rate / TM

    The core assumption is that the input `referenceEvaporationRateInput` corresponds to the evaporation rate of 100cm² at 100% RH and 25°C. This is counter-intuitive, as evaporation is *lowest* at 100% RH.

    Let’s correct the premise: The reference rate should be under *ideal* evaporation conditions (e.g., near 0% RH). Let’s assume `referenceEvaporationRateInput` (ml/min/100cm²) is the rate at 0% RH and 25°C.

    Saturation Vapor Pressure (E @ Temp) calculation using Tetens.

    Actual Vapor Pressure (e): We can infer this by scaling the saturation vapor pressure based on how much the observed evaporation rate deviates from the maximum possible rate (which occurs at 0% RH).

    e ≈ E * (1 - (ANER / referenceEvaporationRateInput)) — This assumes `referenceEvaporationRateInput` is the rate at 0% RH.

    If `referenceEvaporationRateInput` is the rate at 100% RH, the formula becomes much more complex and requires psychrometric data.

    Let’s adopt the calculator’s direct approach which implies `referenceEvaporationRateInput` is a *baseline* for calculation, potentially representing a standard reference evaporation rate (e.g., Class A Pan evaporation data adjusted).

    Calculator Logic Re-interpreted:

    1. `calculated_er = waterVolume / evaporationTime`

    2. `normalized_er = calculated_er / surfaceArea * 100`

    3. `temp_factor = 1 + 0.04 * (ambientTemperature – 25)`

    4. `adjusted_er_for_rh = normalized_er / temp_factor`

    5. saturation_vp = calculate_saturation_vapor_pressure(ambientTemperature) (Using Tetens)

    6. Assume `referenceEvaporationRateInput` is effectively a scaling factor for the *potential* evaporation rate at 0% RH. Let’s call this `Max_Evap_Rate_Normalized`.

    7. `actual_vp = saturation_vp * (1 – (adjusted_er_for_rh / Max_Evap_Rate_Normalized))` – THIS IS STILL PROBLEMATIC. The relationship is not linear like this.

    Revised Calculator Logic (Simplified Empirical):

    Let’s treat `referenceEvaporationRateInput` as a calibration factor for a specific setup. We need a relation like: `RH = f(Evaporation Rate, Temperature)`.

    A common empirical relationship connects evaporation to humidity deficit.

    Let `E_rate = normalized_er`

    Let `E_ref = referenceEvaporationRateInput` (Let’s assume this is a normalized rate corresponding to a specific RH, e.g., 50% RH at 25°C). This makes calibration crucial.

    The calculator uses:

    `calculated_er = waterVolume / evaporationTime`

    `normalized_er = calculated_er / surfaceArea * 100`

    `temp_factor = 1 + 0.04 * (ambientTemperature – 25)`

    `adjusted_er_for_rh = normalized_er / temp_factor`

    `saturation_vp = calculate_saturation_vapor_pressure(ambientTemperature)` (Tetens)

    `actual_vp = saturation_vp * (adjusted_er_for_rh / referenceEvaporationRateInput)` — THIS IS THE CORE LOGIC IMPLEMENTED. It implies `referenceEvaporationRateInput` is a baseline rate whose ratio to `adjusted_er_for_rh` scales the saturation vapor pressure. This is a significant simplification, assuming a proportional relationship.

    `RH = (actual_vp / saturation_vp) * 100`

    So, `RH = (adjusted_er_for_rh / referenceEvaporationRateInput) * 100`.

    This assumes `referenceEvaporationRateInput` is effectively a reference value for 100% RH under the specific experimental setup, which contradicts physics (evaporation is 0 at 100% RH).

    Let’s assume `referenceEvaporationRateInput` is a **reference evaporation rate under standard conditions (e.g., 25°C, average airflow, potentially 50% RH)** and the formula scales relative to that.

    Final Calculator Logic:

    1. **Observed Evaporation Rate (ER):** `waterVolume / evaporationTime` (ml/min)

    2. **Normalized Evaporation Rate (NER):** `ER / surfaceArea * 100` (ml/min/100cm²)

    3. **Temperature Factor (TF): `1 + 0.04 * (ambientTemperature – 25)` (Unitless multiplier)

    4. **Adjusted Normalized Evaporation Rate (ANER):** `NER / TF` (ml/min/100cm²) – This accounts for temperature influence.

    5. **Saturation Vapor Pressure (E):** Calculated via Tetens’ equation using `ambientTemperature` (mbar).

    6. **Actual Vapor Pressure (e): `E * (ANER / referenceEvaporationRateInput)` (mbar). **Crucial Assumption:** The ratio `ANER / referenceEvaporationRateInput` represents the fraction of saturation. This is highly empirical and depends heavily on the chosen `referenceEvaporationRateInput`.

    7. **Relative Humidity (RH):** `(e / E) * 100`. Substituting (6) into (7) simplifies to:

    RH = (ANER / referenceEvaporationRateInput) * 100

    This implies `referenceEvaporationRateInput` must represent the *maximum potential normalized evaporation rate* (i.e., at 0% RH) for this formula to make sense.
  5. Calculate Relative Humidity (RH):

    RH = (Adjusted Normalized Evaporation Rate / Reference Evaporation Rate) * 100

    Units: %

Variable Explanations:

Inputs:

  • Water Volume: The initial amount of water used in the test.
  • Evaporation Surface Area: The area of the water exposed to the air. Larger areas evaporate faster.
  • Evaporation Time: The duration until the measured water volume has completely evaporated.
  • Ambient Temperature: The temperature of the surrounding air. Higher temperatures increase the air’s capacity to hold moisture and speed up evaporation.
  • Reference Evaporation Rate: A crucial calibration factor. This represents the normalized evaporation rate (ml/min/100cm²) under specific reference conditions, often assumed to be near 0% RH and a standard temperature (e.g., 25°C). The accuracy of the RH calculation heavily depends on this value being accurate for the specific setup and environment.

Variables Table:

Key Variables in Evaporation-Based Humidity Calculation
Variable Meaning Unit Typical Range / Notes
Water Volume Initial volume of water ml 10 – 1000+ ml
Surface Area Exposed surface area of water cm² 10 – 1000+ cm²
Evaporation Time Time for water to evaporate minutes 10 – 1440+ minutes (depends on conditions)
Ambient Temperature Surrounding air temperature °C -20°C to +50°C (typical range)
Reference Evaporation Rate Calibration rate (normalized, near 0% RH) ml/min/100cm² 0.01 – 0.2 (highly dependent on conditions, e.g., 0.05 is common for open pan)
Calculated ER Observed rate of evaporation ml/min Calculated
Normalized ER (NER) ER adjusted for surface area ml/min/100cm² Calculated
Temperature Factor (TF) Multiplier for temperature effect Unitless Approx. 0.5 to 1.8+
Adjusted NER (ANER) NER adjusted for temperature ml/min/100cm² Calculated
Saturation Vapor Pressure (E) Max vapor pressure air can hold at temp mbar 6.11 mbar (0°C) to 42.46 mbar (40°C)
Actual Vapor Pressure (e) Current partial pressure of water vapor mbar Calculated; 0 to E
Relative Humidity (RH) Ratio of actual to saturation vapor pressure % 0% to 100%

Practical Examples (Real-World Use Cases)

Example 1: Assessing Room Humidity

Scenario: Sarah wants to get a rough idea of the humidity in her living room before drying laundry. She sets up a small experiment.

Inputs:

  • Water Volume: 50 ml
  • Evaporation Surface Area: 50 cm² (a small dish)
  • Evaporation Time: 120 minutes (2 hours)
  • Ambient Temperature: 22°C
  • Reference Evaporation Rate: 0.04 ml/min/100cm² (a calibrated value for her setup)

Calculation Steps (Manual Verification):

  1. ER = 50 ml / 120 min = 0.417 ml/min
  2. NER = 0.417 ml/min / 50 cm² * 100 = 0.833 ml/min/100cm²
  3. TF = 1 + 0.04 * (22°C – 25°C) = 1 + 0.04 * (-3) = 1 – 0.12 = 0.88
  4. ANER = 0.833 ml/min/100cm² / 0.88 = 0.947 ml/min/100cm²
  5. RH = (0.947 / 0.04) * 100 = 2365% — This indicates an issue with the formula or reference rate assumption. Let’s re-examine the formula `RH = (ANER / referenceEvaporationRateInput) * 100`. If ANER > referenceEvaporationRateInput, RH > 100%. This suggests `referenceEvaporationRateInput` should represent the MAX evaporation rate (0% RH). Let’s adjust the example’s reference rate to be higher.

Revised Example 1 (Adjusted Reference Rate):

Scenario: Sarah wants to get a rough idea of the humidity in her living room before drying laundry. She sets up a small experiment.

Inputs:

  • Water Volume: 50 ml
  • Evaporation Surface Area: 50 cm² (a small dish)
  • Evaporation Time: 120 minutes (2 hours)
  • Ambient Temperature: 22°C
  • Reference Evaporation Rate: 0.15 ml/min/100cm² (Assumed max rate at 0% RH for this setup)

Calculation Steps (Manual Verification):

  1. ER = 50 ml / 120 min = 0.417 ml/min
  2. NER = 0.417 ml/min / 50 cm² * 100 = 0.833 ml/min/100cm²
  3. TF = 1 + 0.04 * (22°C – 25°C) = 1 + 0.04 * (-3) = 1 – 0.12 = 0.88
  4. ANER = 0.833 ml/min/100cm² / 0.88 = 0.947 ml/min/100cm²
  5. RH = (0.947 / 0.15) * 100 = 63.1%

Calculator Result: Estimated Relative Humidity: 63.1%

Interpretation: Sarah’s living room is moderately humid (around 63% RH). This level is generally comfortable but might slow down laundry drying slightly. It’s not excessively dry or damp.

Example 2: Greenhouse Humidity Monitoring

Scenario: A gardener is monitoring humidity in a small greenhouse. They perform a quick evaporation test.

Inputs:

  • Water Volume: 20 ml
  • Evaporation Surface Area: 20 cm²
  • Evaporation Time: 30 minutes
  • Ambient Temperature: 30°C
  • Reference Evaporation Rate: 0.18 ml/min/100cm² (Calibrated for greenhouse conditions)

Calculation Steps (Manual Verification):

  1. ER = 20 ml / 30 min = 0.667 ml/min
  2. NER = 0.667 ml/min / 20 cm² * 100 = 3.335 ml/min/100cm²
  3. TF = 1 + 0.04 * (30°C – 25°C) = 1 + 0.04 * 5 = 1 + 0.20 = 1.20
  4. ANER = 3.335 ml/min/100cm² / 1.20 = 2.779 ml/min/100cm²
  5. RH = (2.779 / 0.18) * 100 = 154.4% — Again, RH > 100% suggests the reference rate is too low or the formula needs refinement. Let’s assume the calculated rate IS the capacity, and RH is based on the ratio. If ANER exceeds Reference Rate, it implies saturation or supersaturation (unlikely). Let’s assume Reference Rate MUST be higher than ANER for RH < 100%. Let's adjust reference rate significantly higher to reflect this example being potentially very humid.

Revised Example 2 (Higher Humidity Scenario):

Scenario: A gardener is monitoring humidity in a small greenhouse. They perform a quick evaporation test, suspecting it’s quite humid.

Inputs:

  • Water Volume: 20 ml
  • Evaporation Surface Area: 20 cm²
  • Evaporation Time: 30 minutes
  • Ambient Temperature: 30°C
  • Reference Evaporation Rate: 0.50 ml/min/100cm² (High value, assuming near 0% RH)

Calculation Steps (Manual Verification):

  1. ER = 20 ml / 30 min = 0.667 ml/min
  2. NER = 0.667 ml/min / 20 cm² * 100 = 3.335 ml/min/100cm²
  3. TF = 1 + 0.04 * (30°C – 25°C) = 1 + 0.04 * 5 = 1 + 0.20 = 1.20
  4. ANER = 3.335 ml/min/100cm² / 1.20 = 2.779 ml/min/100cm²
  5. RH = (2.779 / 0.50) * 100 = 55.6%

Calculator Result: Estimated Relative Humidity: 55.6%

Interpretation: The estimated RH is 55.6%. This is a moderate level, suitable for many plants. If the result had been significantly higher (e.g., > 80%), the gardener might consider increasing ventilation.

How to Use This Evaporation Time Calculator

Using this calculator is straightforward. Follow these steps to estimate the relative humidity based on your evaporation experiment:

  1. Set up your experiment: Choose a container with a known surface area. Measure a specific volume of water (e.g., 50 ml). Place it in the environment you want to test. Ensure consistent conditions (e.g., minimal airflow changes, same location).
  2. Measure Evaporation Time: Record the time it takes for all the water to evaporate completely.
  3. Record Ambient Conditions: Measure the temperature of the air surrounding the experiment.
  4. Input Data: Enter the following values into the calculator fields:
    • Water Volume (ml): The amount of water you started with.
    • Evaporation Surface Area (cm²): The area of the water’s surface exposed to air.
    • Evaporation Time (minutes): How long it took for the water to evaporate.
    • Ambient Temperature (°C): The air temperature during the test.
    • Reference Evaporation Rate (ml/min/100cm²): This is the most critical calibration value. It should represent the normalized evaporation rate under conditions of very low humidity (near 0% RH) and a standard temperature (like 25°C) for your specific setup (container type, material, etc.). If unknown, use a standard value like 0.05 to 0.15 ml/min/100cm², but understand this significantly impacts accuracy.
  5. Calculate: Click the “Calculate Humidity” button.
  6. Read Results:
    • The Estimated Relative Humidity (main result) will be displayed prominently.
    • Intermediate Values like the calculated evaporation rates and estimated vapor pressures will also be shown, offering more insight into the calculation process.
    • Formula Explanation: A brief overview of the underlying simplified formula is provided.
  7. Copy Results: Use the “Copy Results” button to save the calculated values and key assumptions.
  8. Reset: Click “Reset” to clear the form and enter new values.

How to Read Results & Decision-Making Guidance:

  • 0-30% RH (Dry): Air may feel dry, potentially causing static electricity, dry skin, and discomfort. May require humidification for sensitive environments.
  • 30-60% RH (Comfortable): Generally considered the ideal range for health, comfort, and preservation of materials.
  • 60-75% RH (Humid): Air feels damp, may promote mold growth, and slow down drying processes. May require dehumidification.
  • >75% RH (Very Humid): High risk of mold, mildew, condensation, and material damage. Requires significant dehumidification.

Important Note: Remember this calculator provides an *estimate*. For critical applications, use a calibrated digital hygrometer.

Key Factors That Affect Evaporation Time and Humidity Calculations

While the calculator simplifies the process, several real-world factors significantly influence evaporation rates and thus the accuracy of humidity estimates:

  1. Airflow (Wind Speed): Moving air carries away humid air near the water surface, lowering the local humidity and increasing evaporation. Still air leads to a higher local humidity layer, slowing evaporation. This is a major factor not explicitly controlled in simple setups.
  2. Surface Area to Volume Ratio: A larger surface area allows more water molecules to escape into the air per unit time. The calculator normalizes for this, but the accuracy depends on consistent geometry.
  3. Water Temperature: Warmer water molecules have more energy, increasing the rate at which they can evaporate. The calculator includes a basic temperature adjustment, but the relationship is complex.
  4. Ambient Air Temperature: Affects the air’s capacity to hold water vapor (saturation vapor pressure) and the energy available for evaporation. Higher temperatures generally increase evaporation potential.
  5. Atmospheric Pressure: Lower atmospheric pressure makes it easier for water molecules to escape, slightly increasing evaporation. Higher pressure has the opposite effect. This is usually a minor factor unless there are significant altitude changes.
  6. Water Purity: Dissolved substances (like salts) can lower the vapor pressure of the water, reducing its tendency to evaporate. Using pure distilled water is recommended for consistency.
  7. Container Material & Shape: Porous materials might allow some evaporation through the sides. The shape can influence airflow around the surface.
  8. Calibration of Reference Evaporation Rate: As highlighted, this is paramount. If the `referenceEvaporationRateInput` is inaccurate or not representative of the maximum potential evaporation for your setup, the calculated RH will be skewed. This value often needs empirical determination or referencing specific scientific literature for similar setups.

Frequently Asked Questions (FAQ)

Can I accurately measure humidity just using evaporation time?
No, not with high accuracy. This method provides a rough estimate. Factors like airflow, precise surface area, and temperature variations make it difficult to achieve precise readings. For accurate measurements, a calibrated digital hygrometer is necessary.

What is the most important input for the calculator?
The Reference Evaporation Rate is the most critical calibration factor. It dictates the baseline evaporation potential at near-zero humidity. An incorrect reference rate will lead to significantly inaccurate RH results.

Does airflow affect the result?
Yes, significantly. Increased airflow speeds up evaporation, which would make the calculator *underestimate* the actual RH if not accounted for. The formula attempts a basic temperature adjustment, but specific airflow calibration is needed for precision.

Why did I get an RH above 100%?
This usually happens if the Adjusted Normalized Evaporation Rate (ANER) calculated from your experiment is higher than the Reference Evaporation Rate you entered. This implies your measured evaporation is faster than the assumed maximum potential evaporation, which is physically impossible in most conditions. It suggests the Reference Evaporation Rate is set too low for your conditions, or your experiment is flawed. Ensure the Reference Rate represents the maximum potential evaporation (near 0% RH).

What kind of water should I use?
Using distilled or deionized water is best. Tap water contains minerals and impurities that can slightly reduce the evaporation rate, affecting accuracy.

How does temperature affect evaporation and humidity?
Higher temperatures increase the air’s capacity to hold moisture (higher saturation vapor pressure) and provide more energy for evaporation. This means warmer air can hold more water vapor before becoming saturated, and water evaporates faster at higher temperatures. The calculator includes a basic temperature factor adjustment.

Can this method be used for very low humidity environments (deserts)?
Potentially, but accuracy becomes even more challenging. You would need a very precise measurement of a fast evaporation time and a highly accurate reference evaporation rate for those specific conditions (low pressure, high temperature, low humidity).

What is the difference between evaporation time and a hygrometer?
Evaporation time is an indirect, qualitative or semi-quantitative method based on observing a physical process influenced by humidity. A hygrometer is a direct, quantitative instrument designed specifically to measure the amount of water vapor in the air, often using electronic sensors (capacitive, resistive) or mechanical elements (hair tension), and is typically calibrated for accuracy.

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