The greatest inaccuracies were seen when dimmers combined with energy saving light bulbs and LED bulbs were connected to the system.
According to Mr Keyer (lecturer Electrical Engineering at the AUAS and PhD student at the UT) “OK, these were laboratory tests, but we deliberately avoided using exceptional conditions. For example, a dimmer and 50 bulbs, while an average household has 47 bulbs.”
The inaccurate readings are attributed to the energy meter’s design, together with the increasing use of modern (often energy-efficient) switching devices. Here, the electricity being consumed no longer has a perfect waveform, instead it acquires an erratic pattern. The designers of modern energy meters have not made sufficient allowance for switching devices of this kind. When they dismantled the energy meters tested, the researchers found that the ones associated with excessively high readings contained a ‘Rogowski Coil’ while those associated with excessively low readings contained a ‘Hall Sensor’. Frank Leferink (Professor of Electromagnetic Compatibility at the UT) points out that “The energy meters we tested meet all the legal requirements and are certified. These requirements, however, have not made sufficient allowance for modern switching devices. Read full article.