Calculator Inputs
Example Data Table
| Scenario | Wavelength | Target Dose | Measured Irradiance | Reference / Actual Distance | Transmittance | Lamp Remaining | Shielding | Reflective Gain | Uniformity | Safety | Recommended Time |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Quartz-covered UV-C treatment | 254 nm | 60 mJ/cm² | 3.2 mW/cm² | 10 cm / 15 cm | 85% | 90% | 5% | 10% | 92% | 20% | 68.83 s |
| Open surface UV chamber | 365 nm | 120 mJ/cm² | 6.0 mW/cm² | 12 cm / 12 cm | 100% | 95% | 2% | 6% | 95% | 15% | 25.56 s |
Formula Used
Effective Irradiance = Measured Irradiance × Distance Factor × Transmittance Factor × Lamp Aging Factor × Shielding Factor × Reflective Factor × Uniformity Factor
Distance Factor = (Reference Distance ÷ Actual Distance)Distance Exponent
Ideal Exposure Time (seconds) = Target Dose ÷ Effective Irradiance
Recommended Exposure Time = Ideal Exposure Time × (1 + Safety Factor ÷ 100)
Total Energy (J) = Target Dose × Surface Area ÷ 1000
The key unit relationship is important: mW/cm² is the same as mJ/s/cm², so dividing dose by irradiance directly gives time in seconds.
How to Use This Calculator
- Enter the wavelength you are working with for documentation.
- Input the target UV dose required by your chemistry procedure.
- Enter the measured irradiance at a known reference distance.
- Provide the actual working distance and choose the distance exponent.
- Add transmittance, lamp aging, shielding, reflective gain, and uniformity values.
- Include a safety factor if you want a conservative exposure recommendation.
- Enter the treated surface area to estimate total energy and radiant power.
- Press the calculate button to show results above the form, export them, and review the Plotly graph.
Frequently Asked Questions
1. What does this UV exposure time calculator estimate?
It estimates how long a UV source should run to deliver a target dose. It adjusts the measured irradiance using distance, transmittance, lamp aging, shielding, reflective gain, uniformity, and an optional safety factor.
2. Why is irradiance entered in mW/cm²?
That unit makes time calculations convenient. Because mW equals mJ per second, dividing dose in mJ/cm² by irradiance in mW/cm² gives seconds directly.
3. What is the distance exponent used for?
It models how intensity changes with distance. A value of 2 represents inverse square behavior. Some chamber setups or optical systems behave differently, so the exponent is editable.
4. Should I always use a safety factor?
A safety factor is often useful when lamps age, chamber conditions vary, or surface geometry is uncertain. It creates a conservative recommendation, but validated processes should still follow your formal protocol.
5. What does transmittance mean here?
Transmittance is the percentage of UV that actually passes through a liquid, window, cover, or film. Lower transmittance reduces effective irradiance and increases required exposure time.
6. Why include uniformity and shielding losses?
Real systems are rarely perfect. A lamp may create uneven intensity, and containers or fixtures can block part of the radiation. These factors help produce a more realistic exposure estimate.
7. Can I use this for UV-A, UV-B, and UV-C work?
Yes. The wavelength field is included for documentation, while the calculation itself depends on dose and irradiance. The correct target dose still depends on your chemistry application and validation method.
8. Is this enough for regulatory or production release decisions?
No. This tool supports planning and comparison. Critical decisions should also use calibrated measurement devices, validated process studies, equipment documentation, and any applicable compliance requirements.