How We Test 365nm UV Flashlight Output
If you are comparing UV flashlights, a number without a method is barely a number at all. Distance, battery condition, operating time, instrument, beam positioning, and the metric being reported can all change the result. UV Geek uses two separate test systems because sustained output and irradiance at distance are different questions.
LS128: How Well the Light Holds Output Over Time
The Linshang LS128 UV Energy Meter is used for a standardized 32-minute sustained-output run. This test is about output behavior over time. It is not used to rank the absolute power of different flashlight models from their raw close-range LS128 readings.
1. Record the full 32-minute LS128 output curve.
2. Exclude the first 5 seconds of data.
3. Use the 0:05 through 0:15 arithmetic mean as the stabilized baseline, equal to 100% retained output.
4. Calculate the 10-minute checkpoint from the 9:55 through 10:05 arithmetic mean.
5. Calculate the 30-minute checkpoint from the 29:55 through 30:05 arithmetic mean.
6. Divide each checkpoint average by the stabilized baseline and multiply by 100.
The customer-facing metrics are Output Retained at 10 Minutes (%) and Output Retained at 30 Minutes (%). A higher percentage means that particular light held more of its own stabilized starting output. It does not, by itself, mean that light delivers more absolute UV than another model.
LS135: How Much UV Reaches a Sensor at Real Distance
Cross-model distance comparisons use the Linshang LS135 UV Radiometer and are reported as irradiance in µW/cm². Every tested light is fully charged, or placed in its designated fresh-battery condition, then operated continuously for exactly 10 minutes before distance measurements begin.
1. Measure at 10, 20, 30, 40, 50, and 60 feet where applicable.
2. At each distance, sweep or “paint” the beam around the sensor for exactly 10 seconds using the same concentric repeating motion.
3. Record the highest irradiance value registered during that standardized 10-second search.
4. Repeat the same procedure at every distance and for every flashlight.
The result is irradiance at the sensor, not total radiant power. UV Geek does not call LS135 distance readings “total UV output.”
Why the Two Tests Stay Separate
LS128 answers: how stable is this light over a 32-minute run? LS135 answers: after a 10-minute burn-in, how much irradiance reaches the standardized sensor at a stated distance? Mixing the absolute values from those instruments would create a comparison the tests were not designed to support.
Dual-Wavelength Lights
A dual-wavelength light is treated as two separate test records. Each wavelength mode is tested independently, with a full recharge and cool-down before the next wavelength test.
What the Numbers Cannot Promise
Even a strong measured result does not guarantee that every target will fluoresce. Material chemistry, wavelength, distance, surface, background, darkness, and viewing conditions still matter. Testing compares the tool; the target still decides how it reacts.
When you read a UV Geek comparison, look for the instrument, operating time, distance, unit, and exact metric. If those are missing, the number is not ready to support a claim.