Kamstrup tests for high field strengths and avoids complaints
Mobile phones, routers, ID card readers, TETRA radios are just a few examples of modern electronic devices that can challenge a device’s immunity to high field strengths. This may result in the device becoming unusable if it is exposed to some of these and the manufacturer incurs high servicing costs.
By Berit Jarmin
A device’s immunity to very high field strengths (up to 500 V/m) can be tested in DELTA’s reverberation chamber in Aarhus.
These are much higher field strengths than can be achieved in traditional EMC chambers.
“We can offer our clients testing for high field strengths during the development phase and when the product is completed. The standards today, for example CE certification, are a factor of 5-10 times lower than what is required in the real world. They don’t cover the modern scenarios where there are often devices close by, for example mobile phones, hand-held devices and other devices that are close by,” explains DELTA EMC and Wireless specialist, Rasmus Brun Behnke.
When a product is affected by radio fields, it can typically be a problem in relation to the casing, which should be made of metal rather than plastic or in relation to cables.
“It can be expensive manufacturing devices that subsequently turn out not to be immune to high field strengths, both in terms of servicing costs and damage to the manufacturer’s reputation,” says Rasmus Brun Behnke.
“These days people expect that when they place a mobile phone on top of a device it isn’t going to cause a problem.”
Close to zero errors
Kamstrup A/S is based in Skanderborg and manufactures thermal energy meters for district heating plants. The company has used the reverberation chamber during the development phase of a new thermal energy meter.
“The reverberation chamber has given us the opportunity to go beyond the standard tests, even though the product is approved. Our goal is for the device to be as close to error-free as possible,” says Allan Jensen, Development Engineer at Kamstrup A/S.The high field strengths that the device was exposed to revealed some faults that slipped through the net. When the software was “stressed” by the field strengths, it revealed an error related to the initialising value in the radio circuit in the wireless meter.
“We discovered that there was an error, but later on it turned out that the error was corrected by our software initialising the values once an hour,” says Allan Jensen.
It was not the same for the optical communication interface, which stopped working during the stress test. It turned out that the communication baud rate had probably been set up skewed and the fault persisted until a reboot was initiated.
“It makes sense for us to test our products’ immunity to high field strengths during the development phase, we can avoid complaints – even when there’s so few errors,” says Allan Jensen.