UV Curing calculator
UV Lamp Distance Intensity Loss Calculator
Working distance is one of the fastest ways to lose UV intensity. This calculator uses a measured baseline irradiance and the old and new lamp distance to estimate the irradiance at the new cure plane. It is most useful for spot cure heads and flood lamps where distance falloff dominates, and as a quick sanity check before you re-run a full radiometer profile.
What this calculator does
- Estimate how UV irradiance changes when the working distance from a lamp, spot cure head, or LED array changes.
- Use it when raising a lamp for taller parts, changing a fixture height, comparing spot-cure standoff distances, or troubleshooting a dose drop after a mechanical change.
- Estimates the new UV irradiance caused by a working-distance change so engineers can judge whether dose, exposure time, or belt speed must change.
Formula used
- Distance intensity factor = (current working distance ÷ new working distance)²
- Estimated irradiance at new distance = baseline irradiance × distance intensity factor
- Gap to minimum = estimated irradiance - minimum acceptable irradiance
Inputs explained
- Baseline irradiance: Radiometer reading at the current validated working distance.
- Distance intensity factor: Use (current working distance ÷ new working distance)². Example: 2 in to 3 in = 0.444×.
- Minimum acceptable irradiance: Process-floor irradiance needed to keep the dose window valid at the current exposure time or belt speed.
How to use the result
- Use during fixture changes, taller part launches, spot-cure tip setup, lamp-height adjustment, or root-cause work when a radiometer reading drops after maintenance.
- Uses inverse-square style scaling as an estimate. Focused reflectors, line lamps, LED optics, and near-field arrays can deviate materially, so confirm the final setup with a calibrated radiometer at the part surface.
Common questions
- Does UV intensity always follow the inverse-square law? Not perfectly. It is a useful estimate for point-like or spot-cure sources. Focused arc lamps, light guides, and LED arrays use optics that can flatten or sharpen the falloff, so the radiometer reading is the final authority.
- How do I use this for conveyor curing? Enter the baseline irradiance from a belt-height radiometer pass, then compare the validated lamp height with the new part cure-plane height. If the estimated irradiance falls, use UV Dose or UV Conveyor Belt Speed to adjust dwell or speed.
- What decision does the result support? It tells you whether a height change is likely to consume cure margin. If the new irradiance is below the process window, lower the lamp, slow the belt, add exposure time, or requalify the process.
- Why can a small distance change cause a big dose loss? Because irradiance can fall with the square of distance. Moving from 2 in to 3 in can retain only about 44% of the original intensity in a simple geometry, which directly reduces dose unless exposure time increases.
Last reviewed 2026-05-12.