Test Conditions and Equipment

Goal: To conduct field research and demonstrations involving off-grid LED systems.

  • Mills, E. and A. Jacobson. 2007. "The Need for Independent Quality and Performance Testing for Emerging Off-grid White-LED Illumination Systems for Developing Countries." Lumina Project Technical Report #1. [PDF]

Individual LED performance

Test conditions

  • LEDs powered at 20mA; LED serves as load to determine voltage


  • LEDs in 4" Photodyne integrating sphere
  • LED voltage measured with HP 3456A DMM current with Fluke A90 shunts and HP 3455A DMM (+/- 0.25%)
  • Light measured with Tektronix J16 photometer and Licor Photometer (210S)
  • Sphere / J16 calibrated with a Sylvania 796 quartz halogen lamp calibrated by Labsphere

Spectral measurements

  • LEDs in 4" Photodyne integrating sphere
  • Ocean Optics SD2000 spectrometer. Software: OOIBase32, ver.
  • SD2000 calibrated with Ocean Optics LS-1-CAL calibrated lamp to +/- 40K

Illuminance Measurements from Integrated LED Systems

Illuminance distribution on a 1m2 surface

  • light mounted 1 meter from measurement surface
  • illuminance measurements made every 10 cm on a 1 square meter grid
  • illuminance: Extech Datalogging Light Meter (model 401036), (precision 0.01 Lux; accuracy +/-3% of reading)

Lamp discharge curve

  • light mounted in a "dark box" at a distance of 1 meter from illuminated surface
  • light begins test with a full battery; it is discharged completely during test
  • illuminance, current from the battery to the light, battery voltage at 1 minute intervals during discharge
  • illuminance at center of beam measured with an Extech Datalogging Light Meter
    (model 401036; see above for specifications)
  • current measured with a CR Magnetics DC Current Transducer (model 5210-2)
    (accuracy +/-1.0%; output signal 0.5 VDC)
  • voltage and output signal from current transducer measured with a Hobo H08-006-04 Datalogger (8 bit resolution, accuracy +/-3% of reading)

Tests of Batteries

Battery storage capacity

  • measurement made by discharging the battery at a constant current
  • discharge curves are collected using a Cadex C7200 series battery analyzer
    (programmable analyzer; records voltage and current information at 1-minute intervals; 100 - 4,000 mA current range; 1.2 - 16 volts voltage range; NiCd, NiMH, SLA, and Li chemistries supported; +/-1% accuracy)

Tests of Solar Cells

Solar module peak power at standard test conditions

  • outdoor performance measurement of module output made on a clear, sunny day
  • PV module oriented so that it is normal to sun's beam during test
  • peak power estimated from a current-voltage (IV) curve normalized to std. test conditions:1000 W/m2 and 25°C
  • IV measurement collected over 30-40 seconds using a custom data collection system (accuracy +/- 0.5% for current; +/- 0.5% for voltage)
  • module temperature measured with Type-K thermocouple (accuracy +/-2%)
  • solar insolation measurement made with Licor LI200-SA pyranometer (accuracy +/-5%; LI200-SA calibrated annually with Eppley PSP pyranometer)
  • overall accuracy of peak power estimate: +/-10%

Experimental instrumentation and equipment

  • Granderson, J., J Galvin, D. Bolotov, R. Clear, A. Jacobson, and E. Mills. 2008. "Measured Off-Grid LED Lighting System Performance." Lumina Project Technical Report #4. [PDF]
Description Name Accuracy Notes
Power supply TENMA 72-2075   Used in place of batteries
Power analyzer Voltech PM3000A +/-0.05% rdg, +/- 0.05% range Off spec: 0.1% low on voltage, 0.75% high on current
Digital multimeter Datron 1281 +/- 3 ppm, 150 ppm, voltage, current Used to calibrate power analyzer
Oscilloscope Tektronix 7623A +/- 5%  
Integrating sphere   2 m
Integrating sphere +/-3.1% 1m
Standard lamp NBS calibrated 175W incandescent Used w/ 2m sphere
Standard lamp Labsphere calibrated quartz halogen +/- 5% reflectance Used w/ 1, sphere
Photometer Tektronix J16, J6511 probe +/-5% Used with both spheres
Spot luminance meter Minolta LS-110 +/- 2% For luminance
lluminance meter Minolta xy-1 chroma meter +/- 2% For x-y
Rotary table India +/- ~0.5 degrees  
Illuminance meter Minolta T-1 +/-2% For candlepower
Spectrometer analysis software NIST CQS_Simulation_7.1.xls   For quantifying correlated color temperature and color rendering index
Spectrometer Ocean Optics SD2000, w/ OOIBase 32 software +/- 0.01 for x & y coordinate values For quantifying correlated color temperature and color rendering index
99% reflectance standard Labsphere +/- 1% For manual x-y
Spot meter close-up lens Minolta   For luminance
Neutral density filter Tiffen ND1.0   For luminance