Budget Intensity Measurements for Red Light Therapy Part 1 of 3: Tenmars TM-206
How can we measure intensity from red light therapy panels without spending a fortune on professional-grade power meters and 3rd party labs? Is there a way to get cheap intensity measurements at home to help determine proper dosage protocols?
For Red Light Therapy (Photobiomodulation), knowing the intensity is important to make sure it is not too high that could cause eye or skin damage. And of course, we don’t the intensity too low that the light therapy device has no effect.
Knowing the correct intensity allows you to properly calculate your dosage or exposure time especially if you are trying to follow a protocol seen in a clinical study.
Unfortunately, even if you bought from a “major brand” – you probably don’t know the real intensity of your red light therapy panel.
Nearly all brands (big and small) have used inaccurate solar power meters to false advertise the intensity of their LED panels, and are continuing to be misleading about intensity today despite knowing better.
However, in this blog we have devised a way to convert solar power meter measurements to more accurate numbers for intensity!
Quick Guide for Intensity Measurements:
- We obtained a brand new Tenmars TM-206 from Amazon, which is one of the cheapest and most popular solar power meters used by many brands and resellers.
- The meter was sent to our 3rd party lab, LightLab International in Allentown Pennsylvania, and they tested it with identical distances and conditions as their bench-top spectroradiometer.
- With enough data-points, we were able to create a polynomial correction equation (because the Solar Power Meters are so bad that the discrepancy is non-linear).
- So, all you need to do is enter in your Tenmars TM-206 solar power meter measurements into the calculators below and it will convert the number to a more accurate number!
Also press the "R" button to get rid of the decimal point on the meter so it can measure higher numbers.
You will notice the Solar Power Meter units are in W/m^2, so just enter the whole number into our calculator, because it also converts it to mW/cm^2, in addition to the correction calculation.
For example, the popular and suspicously round "100mW/cm^2" number seen here measured on a solar power meter as 1000 W/m^2 (the conversion between W/cm^2 and mW/cm^2 is just one decimal place).
When we enter the number 1000 into the calculator below, then we get 48.8 mW/cm^2. That is likely the real intensity that most brands are referring to when they think they are claiming "100mW/cm^2".
Use this calculator for Red + NIR measurements with the Tenmars TM-206
Use this calculator for NIR-Only Measurements with the Tenmars TM-206
Use this calculator for Red-Only Measurements with the Tenmars TM-206
The Intensity Enigma
Perhaps you purchased a cheap red light panel from a dubious reseller and need to measure the intensity yourself.
Maybe you are a red light therapy enthusiast and want to correlate the clinical science (where they never use Solar Power Meters) to your device and dosing protocol.
More likely; you purchased from a major brand who are surprisingly dodgy about sharing their true intensity measurements. They use asterisks, fine print, and sneakily reveal in their blogs that they are knowingly false advertising their intensity.
Many major brands are proudly brandishing solar power meters as their evidence for their intensity claims, but we know that solar power meters measure falsely high by a wide margin.
If an advertised claim is wrong by 2x; that is not just some mundane measurement error due to lack of standardization, that is false advertising.
When cornered, brands will deflect and tell you that intensity doesn't matter anymore. Instead look at Total Watts or Fluence of J/cm^2 per minute - pay no mind to the fact that they are lying about intensity. Which of course is not only false, but contradictory to their own marketing where misleading intensity always has been front and center on thier product pages.
Our attempt with this blog is to present a breakthrough by using the same cheap solar power meters used for false advertising, and applying a correction calculation to make them more accurate.
Making Solar Power Meters Work For Intensity Measurements
We noticed a long time ago that most solar power meters measure about 2x the real-world intensity when measuring Red and Near-Infrared LED Panels.
As the name implies, Solar Power Meters are cheaply designed for a singular purpose of measuring full-spectrum sunlight. Solar Power meters use a silicone photodiode and they have more responsiveness when measuring longer wavelengths like Red and NIR light.
A typical silicone photodiode responsivity curve from Wikipedia Commons. Look closely how the sensitivity greatly increases as the wavelength it measures increases, especially around 850nm. 
So, when you try to measure an LED panel that has Red+NIR wavelengths with a solar power meter, it is not surprising that we get falsely high measurements.
Many laser power meters also use this same silicon photodiode technology, but apply correction factors based on the wavelength being measured and the sensitivity curve.
Solar Power Meters provide no such correction factor which further implies they were never intended for measuring red light therapy.
This is why we have 3 different calculators for Red+NIR, Red-only, and NIR-only.
Where we have occasionally heard some brands and "experts" claiming that NIR LEDs are much stronger intensity than Red LEDs, but that was due to the measurement error with the solar power meter sensitivity, and not a real phenomenon.
We knew ahead of time to design our experiment separating Red, NIR, and Red+NIR because we understand the reality of how these solar power meters really work.
More Hacks for Intensity Measurements:
Most Red Light Panel companies have measurements obtained by solar power meters. So, you can just request them to send you pictures of the measurements at various distances, and ask for the specific model of the solar power meter used.
For example, MitoRed provides many measurements with a Tenmars TM-206 solar power meter in their blog. So, you can just plug those numbers into our calculators and get a better estimation of intensity from their products.
This way, you don’t even need to buy your own solar power meter, just ask manufacturers to send you pictures of their measurements and then put those numbers into our conversion calculators!
Drawbacks and Limitations for the Calculator:
Like any power measurement, even with expensive laser power meter brands, there are important contexts and limitations to consider.
That is why there are so many types of laser power meters, because they all have slightly different applications and limitations.
- We used the most common 660nm and 850nm LEDs for these correlation measurements. If the panel you are measuring uses different wavelengths or different ratios of Red/NIR, then some error is introduced.
- The maximum intensity measurement for the Tenmars TM-206 is 199.9 mW/cm^2, which is about 92mW/cm^2 when converted to real world intensity.
- Other brands of solar power meters have different calibrations, calculations, and sensitivity – so using other brands will not be as accurate. We will make 2 more calculators for other Solar Power Meter brands in the future, but we can't test them all.
- Even other Tenmars TM-206 units may have different variations of calibrations, age, storage conditions, physical damage, water damage, etc may affect the unit’s calibration and cause measurement drift.
- It is normal to have professional power meters re-calibrated every 1-2 years to make sure they don’t drift, which does not happen for solar power meters (probably cheaper to just buy a new solar power meter every two years).
The older solar power meters tend to measure slightly lower than the new ones. Perhaps it is measurement drift, or that the units were calibrated slightly differently to begin with, or the conditions they have been stored or used.
Overall, the potential drawbacks and errors are minor, especially considering this is a big leap of improvement of accuracy versus not using any correction factor at all.
In fact, this method of using a Tenmars TM-206 with our conversion calculator is likely more accurate than our previous recommendations to use a Laser Power Meter. Since this new method derives a direct correlation between the Tenmars-TM206 and the 3rd party measurements, and we used the same wavelengths that are commonly used in LED Panels.
For the Red/NIR measurements we used a Gerylove COB light because that would eliminate issues if the Red and NIR is not perfectly mixed like in some panels with narrow beam angles or “hot spots”. It also has a wide angle beam so we could measure a wide range of intensities without needing large distances.
For the individual Red and NIR measurements we used a SAIDI BS301 panel for it's high intensity.
Taking the raw data, we compiled it into a Microsoft Excel spreadsheet. We make a simple scatter chart with the ILT950 (professional measurement) as the Y axis, and the Tenmars TM-206 measurements as the X axis.
Then we use the "fit trendline" function in Excel to produce an equation to fit the data. We found the polynomial equation gave the best fit (not a simple linear equation).
A good way to visualize the data is in the graph below, this time we put the 3rd Party Measurements on the X axis, and the corresponding Tenmars TM-206 measurements on the Y axis.
So we can see the experiment matches the theory here. The Red-Only measurements are lower than NIR-Only measurements because it is following along the sensitivity curve that we have shown earlier. The Red+NIR response predictably is in between those two responses since it is now a mix of both wavelengths.
The polynomial response (the slight nonlinear upwards curvature you see in the graphs) also validates why solar power meters have been very unreliable even for "comparison" purposes. Which has led many companies to make the false comparative statement that they were "Twice the Intensity as Joovv", but it was due to this non-linear response by the solar power meters.
Let the Experts Validate the Measurements:
For years we have recommended that consumers divide the advertised intensity numbers of red light therapy panels by 2, or if they are using a solar power meter then just to divide that number by 2.
That seemed unsatisfactory for many people, since people prefer to trust a number that appears on the screen of an unthinking machine. Especially if that number confirms their bias that they have a “powerful” product.
In engineering, scrutinizing measurements and applying logical interpretations to them is a normal part of the job. If we were to believe an inaccurate measurement, then massive problems inevitably arise.
With this blog, we spent a hefty chunk of money to have solar power meters professionally validated. Technically, we professionally invalidated them to show how wildly inaccurate they are.
“As you can see, there are significant differences between our ITL950 and all three of the meters. While these meters may work for solar irradiance measurements, they are not suitable for red, and particularly NIR measurements.”
However, by noticing a trend that solar power meters are consistently wrong by a predictable factor, then we can apply a correction factor to this measurement.
Even one professional laser power meter brand recently posted a video of how to apply a correction factor if their power meter is out of calibration or being used in a context that would knowingly alter the power measurement.
Applying empirical correction factors is a normal part of many engineers’ and scientists’ jobs, especially if it means improving an inaccurate measurement.
This is the first-ever side-by-side measurement comparison with solar power meters compared to a professional spectroradiometer.
By having a 3rd party take the measurements, it makes sure the comparison was conducted as accurately as possible and removes our bias from the situation.
And we hope consumers get some gratification by taking their own measurements and using our interactive calculators to produce more accurate results.
What to do with Accurate Intensity Numbers?
Don’t be shocked that the intensity numbers from your LED Panel are much lower than you expected after using these calculators.
The numbers are usually about half of what has been claimed or measured by a Solar Power Meter, which is what we have been saying for years.
You can look at Alex Fergus’ reviews which show that nearly all of the brands deliver much less intensity than they claimed (except us, but I guess we don’t get bonus points for being honest).
Now that you know more accurate intensity numbers for your red light therapy panel, you also need to “re-calibrate” your mindset about what is an effective amount of intensity.
The narrative of “you need >100mW/cm^2 to be effective” has been repeated by so many brands and affiliate influencers that it is hard to believe that companies are not only delivering much less than 100mW/cm^2, but that people are getting good benefits from those lower intensities.
Perhaps check our other science-based blogs for references to re-contextualize the intensity that you are actually getting:
- Science-Based Intensity Recommendations
- Actual Intensities used in Full-Body Light Therapy clinical studies
- Intensities to stay under for eye safety
- Intensities to stay under to not overheat the skin
- Common Side Effects of Red Light Therapy (usually caused too much intensity)
- Dosing and Timing calculator for usage with accurate intensity measurements
These correction calculators should help red light panel customers obtain more accurate intensity measurements at a small fraction of the cost of getting a decent laser power meter or spectroradiometer.
Of course we always advise true professionals, experts, resellers, brands, and manufacturers to get 3rd party data from a certified light laboratory (and be honest about it). But this blog should help the average consumer or enthusiast to take more accurate intensity measurements.
Knowing the intensity is only half the battle. There are still big questions about how to properly “dose” red light therapy even if we know the true intensity. That perhaps the exposure duration, how often it is used, and distance used – all play important roles for proper dosing.
But we do know clear clinical information like how full-body red light therapy studies have never used anything higher than 50mW/cm^2 on humans.
Which means that companies claiming the “highest intensity in the market” with outrageous intensity numbers are also implying that their products have never been tested for safety and effectiveness.
This is why it is important to use these conversion calculators or more accurate power meters to help consumers understand the real intensity from red light panels.
Until companies start abiding by federal advertising laws to stop misleadingly intensity claims, we have offered a lot of tools and education to help empower consumers to measure and understand the real science on their own.