Electronic spark tester
Since a high profile incident in 1998, where two widely deployed IS certified power supplies failed an intrinsic safety retest, the Australian Coal Association Research Program (ACARP) has funded numerous research projects investigating options for improving IS certification and testing procedures – especially with a view to replacing or supplementing the IEC 60079.11 Annex B Spark Test Apparatus for intrinsically safe circuits.
Since 2011, Mining3, in collaboration with German metrology institute Physikalisch-Technische Bundesanstalt (PTB), has undertaken a research project to develop an Electronic Spark Test (EST) Apparatus– a wholly electronic test apparatus which does away with the mechanical spark contacts and hazardous explosions of the STA. The first phase of this research was completed in 2013. The second phase of research was completed in 2015 and this the third phase of research is now complete.
Unlike the STA, the Electronic Spark Tester (EST) does not require the creation of real sparks or explosions. Instead, a spark simulation is applied as a dynamic load to the device under test (DUT) using a custom designed electronic loading device. The EST then makes a series of measurements of the DUTs voltage and current response to the spark simulation and interprets these measurements based on knowledge of spark physics, developed from experiments undertaken specifically for this project.
The EST measures the response of the DUT and then provides an indication of spark energy and compares this to a known safe limit called an ignitability metric. The information provided by the EST gives engineers and the developer the ability to characterise the response of the DUT and determine its level of safety or level of failure rather than a pass or fail as is currently the case with the STA.
By removing the requirement for a specialised laboratory, the EST will enable a new approach where Intrinsic Safety (IS) testing can be conducted by developers, test houses, manufacturing facilities and on site personnel to ensure the ongoing safety of devices. Furthermore the EST will give the ability for every IS power supply to be tested as they roll off the production line, rather than a single device.
The new Electronic Spark Tester (EST) provides a more reliable, informative and versatile test method, and an intrinsic safety approach that will deliver better risk management in explosion protection.
Mining3 has published a report detailing the project results and submitted a draft proposal to the International Electrotechnical Commission (IEC) for implementation into the IECEx 60079 standard. While continuing with this research, the team at Mining3 are providing a new design review and prototype testing service to assist manufacturers with meeting the requirements of the current standards.
In September 2015 Mining3’s EST research team received an ACARP Research and Industry Excellence Award for the project.