Cover story
Achieving 99% Improvement in EMC Compliance for MEMS Systems
Richard Anslow, System Applications Engineer and Ricardo Zaplana, Design Engineer, Analog Devices M
EMS systems are used for vibration monitoring in railway, wind turbine, motor control and machine tool applications to
enhance safety, reduce costs and maximise the useful life of equipment. MEMS sensors, with their superior low frequency performance, enable earlier detection of bearing defects in railway and wind turbine applications compared to competing technologies. Significant cost savings are coupled with higher detection rates for equipment defects, ensuring compliance with stringent safety standards. Wide bandwidth (0-23kHz), low noise performance and wide vibration measurement range (2-200g) are all required for vibration monitoring. This is easily achieved using Analog Devices’ broad MEMS portfolio. Wired communication systems are used for vibration monitoring where raw data from several sensors is gathered, or where raw data is used for real-time control. There are several challenges in implementing a wired condition- based monitoring (CbM) system. One key challenge is electromagnetic compatibility (EMC) robustness when operating over several metres of cabling, which can be subjected to indirect lightning surges, electrostatic discharges and environmental noise such as switching of inductive or capacitive loads. Poor robustness
to EMC disturbances can intermittently or permanently degrade the quality of data gathered from the CbM systems. Over time, poor quality data can lead to incorrect decisions around asset health and maintenance.
Why Is System-Level EMC Simulation Important? Design for EMC is notoriously difficult to get right the first time, with even small changes in circuits or lab test setup dramatically affecting test results.
Modern product development schedules include a parallel EMC compliance task. Design for EMC should be as seamless as possible, but this is often not the case, with EMC problems and lab testing delaying product release by months. The virtual lab EMC simulation approach helps engineers solve EMC problems much faster compared to lab test alone. The virtual lab simulation approach helps to solve key problems in achieving EMC compliance because: •Increased integration and component density in modern PCB designs leads to complex problems, with multiple EMC failure paths. Simulation can help to determine the best EMC mitigation technique in a more flexible and time-efficient way compared to lab testing alone.
•EMC standards are sometimes ambiguous, which means different test results are achieved
if the circuit is tested in different ways. Using simulation allows much faster test changes and results compared to lab testing.
•The entire system needs to be built to ensure EMC compliance, including cable choice, length and shielding, as well as measurement setup. Using simulation, real measurement probe effects can be ignored, and cable models can be changed in seconds rather than hours.
•The equipment under test can differ from the customer’s installation, leading to different test results. Using simulation, the real customer application can be better modeled and understood.
•Existing simulation tools are not unified, and simulation models are not readily available for cables and PCB geometries. The virtual lab allows integration of cable, PCB, and passive and active component models, with more accurate results.
What Are the Benefits of System- Level EMC Simulation? System-level EMC simulation results in much faster time to market for products. This is achieved through: •Rapid identification of circuit weaknesses and targeted recommendations for improvement.
•99% improvement in capturing EMC failures and understanding the failure mechanisms.
•Significant cost savings – several design and test iterations do not need to be performed.
•Significant time savings – the design does not need to be iterated several times, which cuts down the development schedule by months when you consider the lead time for PCB board layout, manufacture and assembly.
The EMC Challenge Figure 1: A 2-wire IEPE sensor interface with shared data and power architecture
Shared power and data wire architectures (phantom power) are often used to reduce system cost and PCB area (fewer PCB connectors). The IEPE standard, widely used with vibration sensor technology, supplies a constant current source to the vibration sensor, with the sensor output voltage read back on the same wire, as shown in Figure 1. This 2-wire system means that power
06 July/August 2021
www.electronicsworld.co.uk
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