Why Use a LED Light Meter for Measuring Light

Did you know that a standard light meter may not be capable of measuring LED light? If you have previously used a standard light meter to measure LED light, chances are you have collected inaccurate or inconsistent results. 

This article will explain how LED light meters differ from standard light meters and why it is essential to have the right meter for the job.

About LED Light Meters 

LED lights are replacing other types of lighting as they are more efficient, last longer and save energy (and money!).

Standard and LED light meters are used to measure illuminance. Illuminance results will appear in a light meter display as either Lux or Footcandles. Lux and Footcandles measure the same thing. The difference is that the footcandle is an imperial measure, while lux is metric. Lux is the widely-used term used in Australia.

Standard light meters are calibrated to match the response of the human eye to light, defined by the CIE photopic curve (see Table 1 below). A typical human eye will respond to wavelengths from about 380 – 740 nanometers (nm).

Table 1 The CIE Photopic Curve - Standard light meters are calibrated to match the response of the human eye to light.

Difficulties emerge where standard meters cannot measure light accurately outside of this curve. Measuring light emitted from LED lights is an example of such a problem.

See the comparison of the three graphs below. There is a spectrum of typical eye sensitivity and intensity of incandescent bulbs and LED bulbs.

Table 2 Wavelength and Intensity charts of visible light to the human eye and light emitted from cool white and Incandescent light sources.

You can see a couple of things from the graphs above.

The first interesting point to note is the high amount of invisible light emitted as heat around 650nm on the incandescent bulb. That’s essentially money burning in wasted energy, which has led to the widespread use of the LED light.

However, with the cool white LED light you can see a significant amount of visible light as well as a high energy spike in the blue spectrum between 400-500nm. Comparing this spike in cool LED light with the human eye sensitivity graph that standard light meters use, it’s easy to understand where the measurement errors can occur.

Why does measuring light outside of this range matter?

One key point is health. Studies are coming out in regards to blue light and its potential impact on health. Being exposed to blue light sources in the afternoon and evening may suppress the secretion of melatonin, shift your circadian rhythm and can result in adverse health effects associated with poor sleep.

Note: Even with ‘warmer’ style LED lights – don’t be fooled they don’t emit a red wavelength. The red and orange hues come from masking the blue light with high amounts of orange and yellow. Some warmer style LED emit less blue light than others, but there is no indication of this on the LED packaging. The only way to check this is through a light meter.

See table 3, an excellent example of a warmer style LED light; this falls in line with the human eye sensitivity chart and does not have the high blue energy spike shown by the cool white LED.

Table 3 Wavelength of a warm white LED light. The warm white LED lines up with the human eye sensitivity chart in table 2.

The solution

LED light meters are designed to overcome the issue of erroneous results by using specific algorithmic calculations to measure the LED light spectrum, which may not necessarily fall within the CIE Photopic curve. A light meter can check LED lights to ensure they fall into the desired range to have minimal disruption to your life.

Some meters can even go one step further and break up the LED spectrum and provide results for blue, green, purple, yellow or red wavelengths.

Examples of LED Light Meters

Listed below are some examples of light meters that are built to measure LED light, available at Instrument Choice. The examples below have differing specifications and are at different price points to suit all budgets and needs.

Professional Digital Light Meter

Product Code: IC1584LM

Boasting an accurate and fast sample rate of 1.5 seconds, the IC1584LM can store minimum and maximum values for easy comparisons.

Quick Specs:

Output: Lux and Footcandles

Lux Range: Up to 400,000

Accuracy: ±5%

Lens Cap: Included

Zero Calibration Function: Yes

Adjustable Colour Temperature: No

Testboy TV 335 Digital LED/Lux Meter

Product Code: IC-TTV-335

Practical and robust yet budget-conscious the IC-TTV-335 is ideal for measuring LED and other artificial light sources.

Quick Specs:

Output: Lux and Footcandles

Lux Range: 20 lx, 200 lx, 2000 lx, 20000 lx, 400000 lx

Accuracy: ±3%

Lens Cap: Included

Zero Calibration Function: Yes

Adjustable Colour Temperature: Yes

Colour LED Light Meter

Product Code: LT45

This LED Light meter is excellent for monitoring and optimising light levels in a wide range of applications.The LT45 measures both white and colour LED lights, and it also can store or recall up to 99 data point records.

Quick Specs:

Output: Lux and Footcandles

Lux Range: 400 lx, 4000 lx, 40000 lx, 400000 lx

Accuracy: ±3%

Lens Cap: Yes

Zero Calibration Function: Yes

Adjustable Colour Temperature:Yes -white, Red, Yellow, Green, Blue, and Purple LED

Conclusion

It is vital that if you intend to measure LED light, you use a light meter that is capable of doing so. Standard light meters are not designed to measure the light spectrum that LED lights emit. To avoid errors and confusion with results when measuring LED lights, ensure you are using the right meter for the job.

Unsure if your light meter can measure LED light, need help finding a light meter to suit your application or want more information on any of the above products? Contact one of the Instrument Choice Scientists. We’re here to help!

Call 1300 737 871 or email [email protected].