To measure the power draw, MyBroadband used a PZEM-004T based monitoring system to see how they compare with the rated values.<\/p>\n
The measurement module measures AC voltage, current, real power, frequency, and power factor with an accuracy of better than 1%.<\/p>\n
We then compared the power draw with the light emitted by each bulb, measured in luminous flux, to get an efficiency measurement.<\/p>\n
Luminous flux is a measure of the total light emitted by a source and is often used as a point of comparison between different lights, usually indicated on light bulb packaging in lumen (lm).<\/p>\n
Luminous flux can be difficult to measure precisely, as all the light in all directions from the source needs to be captured.<\/p>\n
Illuminance, measured in lux (lx), is the intensity of light over a surface area and is much easier to measure.<\/p>\n
If only one square metre of a surface is lit up by a 1-lumen source, then the brightness will be 1 lux.<\/p>\n
By making some assumptions about the distribution of light, lumens can be calculated from a lux measurement.<\/p>\n
If one assumes that a light bulb is equally bright in all directions (which is not entirely true), the lumens can be calculated from a spherical surface area based on the distance of the lux measurement.<\/p>\n
The error from this assumption can be reduced by taking measurements from different directions relative to the light bulb and averaging these values.<\/p>\n
For comparison between light bulbs, MyBroadband took measurements with the light bulb inside a large cardboard box to reduce the influence from other sources.<\/p>\n Only a small gap in the box was opened to allow for the measurement to be taken using a lux meter built into a smartphone.<\/p>\n While this is not a calibrated instrument, it should suffice for this experiment.<\/p>\n Nine measurements were taken from the side, bottom, and top of each bulb. The average for each location was then calculated.<\/p>\n To get to a final lumen value, the averages were weighed 4:1:1 for the sides, top and bottom, to get an estimate of the total luminous flux all around the bulb.<\/p>\n These values were then normalized against the advertised lumens for each bulb.<\/p>\n Although this method is not perfect, the estimated luminous flux still provides a comparable value between light bulbs as all the same assumptions have been made for the different bulbs.<\/p>\n The tests revealed that LED and incandescent bulbs get up to a consistent and final brightness very quickly after being switched on.<\/p>\n CFL bulbs, in comparison, slowly increase in brightness over around a minute after being first switched on.<\/p>\n CFL and incandescent bulbs take some time to stabilise with regards to power draw, while LED bulbs immediately draw power consistently after being switched on.<\/p>\n To account for these differences, each bulb was on for around 2 minutes before taking any measurements.<\/p>\n The results revealed big differences in efficiency between LED, CFL, and incandescent bulbs.<\/p>\n The LED globes had the best average efficiency at 96 lm\/W, with CFL bulbs coming in at 58 lm\/W, and incandescent bulbs only achieving 9 lm\/W.<\/p>\n This is in line with what has been published about the average efficiency of these types of bulbs.<\/p>\n Another interesting point is that both LED bulbs and 75% of the CFL bulbs were measured to have higher luminous flux than advertised.<\/p>\n Both incandescent bulbs in the test measured lower than advertised values using our methodology.<\/p>\n The table below provides an overview of the results of our light bulb testing.<\/p>\n![\"\"](\"https:\/\/mybroadband.co.za\/news\/wp-content\/uploads\/2022\/01\/Current-draw-test-640x426.jpg\")
<\/a><\/p>\n![\"\"](\"https:\/\/mybroadband.co.za\/news\/wp-content\/uploads\/2022\/01\/Box-test-640x426.jpg\")
<\/a><\/p>\n