Got my lux meter... now what?

LED Flashlights – General Info
1

I just got an “HS1010A” lux meter that was recommended here on BLF:

http://www.gamesalor.com/product_4339_Lcd-display-Digital-light-meter-1-200000-Luxmeter-High-precision-portable-Light-photo-Luminance-meter-instrument.html

It came with some instructions (a double-sided, folded piece of paper), but reading that “hurts my head” because of what appears to be a really bad translation.

So, I was wondering if someone here who has this lux meter could provide a simple step-by-step HOWTO use this to measure the performance of a flashlight?

Thanks!

Jim

2

Make an integrating sphere ?

3

That might come later, but need to start at simple stuff…

4

Instructions for measuring throw in candelas:

  1. Turn on meter
  2. Hold light at a known distance (recommend at least three meters). Best to use a tripod of hold nice and steady.
  3. Turn on light, point the center of the hotspot directly at the metering surface (white circle)
  4. Note the lux reading
  5. After 30 seconds, note the lux reading.

Now convert to candelas. I use LEDRise

  1. Enter lux reading
  2. enter distance to meter
  3. Enter 90 for angle
  4. Click on Lux to Candela button
  5. divide by 1,000 for candelas (cd) or 1,000,000 for kcd

Measuring throw is typically easier than measuring lumens, and still gives a good relative indication of mod improvements.

Enjoy! :slight_smile:

P.S. that meter has a max hold function which can be useful if you cannot read the display from your measuring distance. The button is labelled MAX and cycles through normal, Max and Min.
Edit: I have the same exact meter from the same seller.

5

Thanks for that step-by-step!

I’m slowly slogging through their “manual”, and it looks like you can set it up to take ‘x’ (up to 50) samples), and collect the samples, and then you can get the meter to tell you the min and max captures, or scroll through the captures.

I think that’s what the manual says, but like I said, I’m having a really hard time reading it, because of the grammar :(, so I have to read it almost a paragraph at a time, then take a break. I’m not kidding :(…

From what you said, I can use this meter to measure the hotspot lux? Is there a way to determine the “lumens”? Or is this just for the lux/Kcd (they call it “FC” (foot candles?)?

6

Lumens requires an integrating space of some kind. You can use anything from a real IS to a bathroom with white walls. I’m not kidding, several BLF members get rather accurate measurements with their integrating bathrooms.
The main additional items you need are a calibrated sources. ideally, you calibrate with more than one known output light. I used a few known-bin XM-L bare emitters for this task, driven from a lab bench power supply. With some careful measurements, I was able t get my home-build integrating sphere box to produce reasonably accurate results. I suspect that it is not accurate with all beam profiles.
For the integrating bathroom:

  • Set the meter on a countertop (preferrably always in the same spot, ensure it will not be shaded by anything)
  • Point the light at the ceiling above the meter (near the center of the ceiling)
  • turn off any lights in the room
  • note the lux reading
  • after 30 seconds, note the lux reading.
    To ‘calibrate’ do this with your known source, divide the lux reading by the known lumen output. The result is your lux-to-lumen factor.
    For any future measurements, simply divide the lux by the factor to get lumens.

Note: determining when to take the reading of the known light is the trick; temperature will affect output and any error here will affect all subsequent readings.
Again, if your main goal is relative results for mod comparisons, actual calibration isn’t that important. If you want to use it to determine if one light is brighter than the other, this should be OK too.
Beam profile will introduce some variability; only a high quality IS will give consistent results independent of beam profile.
Comparing to the results of others, now that requires caution. I do it occasionally (Tom E and I get similar results on similar mods), but generally this can cause more headaches than it is worth.
Enjoy! :slight_smile: