As LED usage skyrockets with sustained government support, quality control and standardisation are key to building consumer confidence in this new lighting technology. Read on to learn more about the range of LED T&M equipment available to manufacturers
By Baishakhi Dutta
LEDs are taking the lighting industry by storm. And the only way LED performance can be guaranteed is to ensure standardisation during production, ensuring the devices meet end-user requirements across a range of operating parameters. Drivers are an important component in the performance and reliability of LEDs. There is a wide range of testing equipment available in the market for LED drivers. Let us take a look at the latest test and measurement systems available in the market for LEDs.
Why LED testing is required
Government as well as private procurements are the key factors driving the LED test and measurement industry. For lighting products to be sold in the market, they must meet certain national industry standards. An LED product has to be industry-perfect on all parameters, which can only be achieved by thoroughly following the requirements of the Compulsory Registration Order (CRO) scheme, the Bureau of Indian Standards (BIS) and National Accreditation Board for Testing and Calibration Laboratories (NABL).
BIS: The quality goals can only be met by standardisation. Generally, this involves the process of formulating, issuing and implementing standards. The Bureau of Indian Standards has provided traceable and tangible benefits to the economy in a number of ways — providing safe, reliable, quality goods; minimising health hazards to consumers; promoting exports and import substitution; controlling the proliferation of product varieties, etc. For more information, visit: http://www.bis.org.in/bis_overview.asp
CRO scheme: The supply of low cost and low quality electronic items has a long term and adverse effect on quality conscious manufacturers. In order to address this issue, what was earlier the Department of Electronics and Information Technology (DeiTY), and has been recently converted to the independent Ministry of Electronics and IT (MeitY), had started the Compulsory Registration Order (CRO) scheme. Under this scheme, assistance is provided for setting up laboratories to test electronic goods. The order mandates that electronics manufacturers conform to the specified standards and get a registration from BIS (Bureau of Indian Standards).
For more information, visit: http://deity.gov.in/esdm/standards
NABL accreditation: This is about assessing and determining the reliability of data that the testing laboratories are generating. The procedure of inter-laboratory comparison is used to validate the results of testing. All accredited laboratories have to participate in at least one successful inter-laboratory comparison. They have to follow ISO/IEC 17025 specifications to maintain quality management systems in testing and calibration. For more information, visit: http://www.dst.gov.in/autonomousstinstitutions/national-accreditation-board-testing-calibration-laboratories-new-delhi
The parameters that need to be tested
The explosive growth of LEDs as a replacement for fluorescent and incandescent light sources is driving the need for more stringent performance standards to be set and adhered to by the designers of displays and luminaires. Optical testing confirms accurate binning, increases yield and validates LED performance, thereby reducing the overall cost of manufacturing. Various parameters including intensity, flux, directivity, power consumption and colour give a quantitative idea of an LED’s performance, thereby ensuring its improvement over preceding versions. Testing processes gain speed during manufacturing to maintain production volumes.
An essential parameter to be considered is longevity. Unlike incandescent bulbs, predicting LED lifetime is difficult due to its long term of service, and presently, there are no common standards being followed to extrapolate an LED’s expected life. Instead, a lumen value and an approximate time is printed on the packaging, indicating when the device will cut down to 70 per cent of its initial intensity.
In this context, Kishor Thakare, marketing manager, South India, Meco Meters, says that accuracy plays a very crucial role in the LED testing procedure since this is what makes the testing procedure complete.The basic parameters that must be considered when implementing an LED device into your design are listed below.
How testing can help the LED industry
Efficient and reliable test-retest capabilities in industrial as well as other applications, for various parameters like LED binning and process monitoring, are highly desirable. A spectrometer should be quick, accurate, sensitive and reliable in measurement, be it for LEDs used in exterior lighting or for the daily quality control in LED production.
Miniature spectrometers are enabling new applications and implementations like quality control and product analysis in the lighting industry. These spectrometers provide flexible solutions for a wide range of upcoming applications in the LED industry today.
Developers and manufacturers of lighting solutions harness the power of a spectrometer to solve a variety of problems.
Thakare mentioned that the accuracy of the product, its reliability, portability and cost are some of the important factors that a buyer should keep in mind while purchasing T&M products.
Third party testing
Third party testing plays a key role in product certification. It provides an unbiased assurance that products meet the requirements of industry standards and energy efficiency programmes, apart from confirming consistency through proficiency tests and factory inspections. Typical areas of testing and measurement include total luminous flux, luminous efficacy, correlated colour temperature and electrical power consumption, among others. While most tests are done directly within the lab, they can also take place at a company’s manufacturing facility, if necessary. In such cases, the manufacturer must participate in a data acceptance programme with the third party lab, which is an industry known methodology that ensures testing results remain unbiased. Data acceptance programmes can be used for both performance and safety testing.
Emerging trends in testing
- Dedicated instruments to check electrical and optical parameters
- As the cost of LED lights is going down due to mass production techniques, there is a need for testing multiple LED lights at a time
- As light measurement is mostly about data, it is essential to have a device that can accurately collect data over the wide range of light intensities
- There is a need for a single device to measure various parameters instead of having multiple devices for each parameter
- Meters to demonstrate the difference between the power consumed by LED lights compared to conventional lights at the point of sale
A few testing labs in India
- TUV Rheinland
- TUV Nord
- TUV SUD
- UL
- STQC
- SGS
| Electrical: |
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| Optical: |
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| What to test | T&M device used | Purpose of the tests |
| Lux | Lux meter | To measure lux levels and light levels |
| Lumens | Integrated sphere | To measure the lumen value of the light source |
| Spectrum data | Spectrometer | To measure the spectral composition of the light source |
| Thermal images | Thermography | To measure thermal images and temperature |
| Power measurement | Power meter | To measure wattage, voltage and power factor |
| Flux (flow rate per unit area) measurement | Goniophotometer | For measuring luminous intensity distribution |
| Dimmers | Leading edge dimmer | Used for dimming tests that measure the range and gradation in brightness |
| Spectral energy | Spectrum analyser | It is used to measure radio interference |
| Analogue/mixed signals | Signal analyser | To check the input (and often output) of analogue or digital signals |
| Voltage measurement | Oscilloscope | Used for measuring transformer and driver voltage output |
| Flicker measurement | Colorimeter | Used to measure light flicker |
| Colour lighting measurement | Colour meter | Used particularly for narrow-band LED colour-light measurements |
| Sorting and binning LEDs | Spectroradiometer | For online production applications for radiometric, colorimetric, photometric and spectral-radiometric measurements |
A few Testing devices available in the market
Rishabh’s multimeter (Model: 6016)
The 6016 new digital multimeter offers safety, high resolution, a large range count, reliability, ruggedness and, in short, is a complete tool for LED testing.
Key features
- 60,000 count true RMS measurement with high crest factors
- Data logging up to 32,000 readings with real-time stamp
- 100kHz bandwidth for voltage measurement
- 1kHz low pass filter mode for VFD applications
- Temperature measurement with J, K, Pt100 and Pt1000 sensors
- Self-battery voltage measurement
Contact details: www.rishabh.co.in
Meco’s lux meter (Model: 930T)
This product is extensively used for measuring luminance in workplaces and the intensity of light with user selectable units of lux and footcandles (fc). This range of lux meters is known for providing highly accurate results even in extreme conditions.
Key features
- Wide range from 0.1 ~ 200,000 lux
- Backlight
- Sensor with extension cord to measure lux of areas not reached
- Max./min. function to know maximum and minimum value of lux
Contact details: www.mecoinst.com
Instrument Systems’ integrating spheres (Model: ISP 1000)
One of the most important tests in light measurement is the assessment of the total radiant power or luminous flux of light sources using integrating spheres.
Key features
- An inner diameter of 500mm
- CIE 127 compliant for measuring luminous flux of LEDs
- 150mm minuscule port for coupling from the side
- Internal lamp post for mounting test sources in the centre
- Auxiliary light source
Contact details: www.konicaminolta.us
Everfine’s goniophotometer (Model: GO-2000)
A goniophotometer is a photometer that measures the angular dependence of optical quantities. It is used for ascertaining the luminous intensity distribution, luminous flux, spatial colour distribution and luminance distribution of lamps and luminaires.
Key features
- The light source rotates around both the horizontal axis and the vertical axis, and the range of rotation is ±180°
- Accuracy of angle is up to 0.05°
- It has a pre-amplified and constant temperature photometer head, CLASS L (f1’<1.5 per cent) or CLASS A (f1’<3.0 per cent)
- The measuring range of illuminance is 0.0001lx— 200klx
- Linearity of photometry is 0.2 per cent
Contact details: www.everfine.net
Everfine’s spectrophotometer (Model: CY-1000)
Spectrophotometers are widely used to measure the spectral, photometric and colorimetric parameters of all kinds of lighting sources, which include relative spectral power distribution P(λ), chromaticity coordinates (x,y and u,v), correlated colour temperature (Tc), colour rendering index (Ra), dominant wavelength, peak wavelength, spectral bandwidth, colour purity, colour ratio, SDCM, luminous flux, illuminance, luminance, spectral transmittance and reflectance, etc.
Key features
- Measuring range of luminous brightness: 0.01mcd/m2—100cd/m2
- Photometer head: Class A V(λ) approximated and pre-amplified
- Linearity of luminous brightness: 0.2 per cent (whole range, superior than PMT by 1-2 orders)
- Repeatability of luminous brightness: 0.1 per cent
- Excitation source: 6500k
- Automatically-controlled exciting time
- CIE 0/45 illumination/detection condition
- Maximum time of afterglow measurement: 100h
- Sample interval
- Colour measurement can be equipped with Haas-2000 high accuracy array spectroradiometer
Contact details: www.everfine.net
Meco’s infrared thermometers (Model: IRT550P)
An infrared thermometer is used to measure the amount of heat present in the measuring object by calculating the energy emitted from it.
Key features
- Wide range (-50°C ~ 550°C) to measure the temperature of LED lights
- °C/°F selection
- Auto power-off to save battery life
- Backlight display
- Max./min. function to know maximum and minimum value of temperature
Contact details: www.mecoinst.com
Quick tips
Though orientation is not a part of the CRO scheme, yet it is good to check this aspect of LEDs. The light emission process of an LED is not affected by orientation. Yet, orientation can change the thermal conditions for the LEDs used in the product, and hence affect the light output of the product.
The quality of the testing is only as good as the quality of the equipment used. While manufacturers are able to conduct their own testing, third party testing laboratories are required because small variances in tolerances in the testing equipment can affect the measured value.
For LEDs, a very specific tolerance is required for the input source, directly affecting the output values produced. Making sure the test is conducted under the right conditions is also critical. The temperature sensor should also be shielded from the direct optical radiation from the product. The mounting of the product is also important, as the location can affect heat flowing away from the product.
