Ensuring EMC compliance
Every developer of an electrical or electronic device is faced with the same problem: in the end, the device must comply with international electromagnetic compatibility (EMC) guidelines regarding emissions and immunity. In the age of the substitution of mechanical and mechatronic systems by purely electrical ones, EMC is becoming increasingly important.
The use of electrical energy always involves its transformation into other forms of energy, such as radiant energy (light bulbs), mechanical energy (motors) or heat. Transforming or transporting electrical energy causes electromagnetic fields that do not necessarily remain within the electrical appliances, but may also spread outside the appliance into the air or to the power supply. Fields that are allowed to spread freely may penetrate electrical appliances and affect their performance. These fields are perceived as interference.
EMC interference sources include the following:
- Electromagnetic fields, deliberately generated by transmitters operating in frequencies ranging from a few kHz up to more than 30 GHz (microwaves).
- Lightning strikes.
- Switching events in low-voltage networks cause high-energy surges.
- Switching events in power electronics (switching power supplies) cause high-frequency transients and flicker.
- Nuclear electromagnetic pulse (NEMP) caused by a nuclear explosion.
- Electrostatic discharges (ESD).
- High-frequency signals caused for instance by load changes in microprocessors or when using frequency converters.
According to the law, electrical appliance manufacturers must ensure EMC compliance by putting in place appropriate protection requirements. If attention is paid too little or too late to the EMC requirements, there is a threat of delays in obtaining marketing authorisation, with all the potential negative consequences for a company. A subsequent re-engineering leads to rising costs; the roadmap leading to series production must be revised and, in the worst-case scenario, supplier loyalty is at stake.
Industrial touch panels are one example of a product where EMC compliance is essential. Other electrical equipment in the vicinity should not disturb the operation of the product, and the product should also not disturb other equipment.
To obtain an EMC-stable input system, two main sources of interference have to be considered. The first source of interference is the displays which have to be integrated behind the touch panel and the power supplies being clocked. The EMC standard IEC 61000-4-3 refers to these interference sources.
Furthermore, the EMC standard IEC 61000-4-6 defines conducted coupling of interfering voltage peaks and frequencies, to eliminate these interference signals that the HMI system operates with positional accuracy without deviation of the touch function. This in turn does not cause false alarms and is a prerequisite for achieving EMC compliance to Class A.
With optimised AD converters in the evaluation electronics of the PCAP controller, increased signal voltages through charge pumps, special algorithms (frequency-hopping method and hardware/software filters) and interference sources can be suppressed comprehensively. With a sensor design specially adapted to the electronics, an optimum signal-to-noise difference is achieved.
Your product should comply with EMC standards and regulations. Prior to the final EMC test at an accredited test lab, it is recommended to investigate the EMC behaviour at the early design phase by performing pre-compliance tests. SCHURTER can assist with this process to help find the optimal EMC solution for each user’s specific application.
The company can conduct EMC tests, provide interference suppression for equipment, fabricate specific product samples, and support product life cycle from development all the way to series production. In addition to providing customer-specific products such as filters and inductive components, it offers a wide selection of standard EMC products including power entry modules with line filters, chokes, and one- and three-phase block filters. For more information, visit http://emc-service.schurter.com.
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Every electronic device needs some kind of protection, depending on where and how it will be used.