哪些产品可以免除EMC测试？

2016-01-11 14:17:17 栏目：通讯专栏

随着电气电子技术的发展，家用电器产品日益普及和电子化，广播电视、邮电通讯和计算机网络的日益发达，电磁环境日益复杂和恶化，使得电气电子产品的电磁兼容性(EMC电磁干扰EMI与电磁抗EMS)问题也受到各国政府和生产企业的日益重视。电子、电器产品的电磁兼容性（EMC）是一项非常重要的质量指标，它不仅关系到产品本身的工作可靠性和使用安全性，而且还可能影响到其他设备和系统的正常工作，关系到电磁环境的保护问题。欧共体政府规定，从1996年1月1起，所有电气电子产品必须通过EMC认证，加贴CE标志后才能在欧共体市场上销售。此举在世界上引起广泛影响，各国政府纷纷采取措施，对电气电子产品的EMC性能实行强制性管理。国际上比较有影响的，例如欧盟2004/108/EC指令（即EMC指令）、美国联邦法典CFR 47/FCC Rules等都对电磁兼容认证提出了明确的要求。
但并非所有的设备都需要做EMC测试，在CE EMC指令中就提到一些设备可以免除EMC测试，他们称之为“Inherently benign equipment”（固有良性设备）。
那么什么样的设备属于EMC固有良性设备呢？同时满足下面两个条件的设备视为EMC固有良性设备：
1. 其固有物理特性使其不能产生或促成超过无线电和电信设备和其他设备按预期运行所允许的电磁发射等级
2. 在预期环境中，其在正常的电磁干扰呈现下，其运行没有不可接受的性能退化
这个定义有点拗口，具体来讲，如下设备（如果他们不包含有源电子器件）可以排除在CE EMC指令之外：
1. Cables and cabling, cables accessories, considered separately；
2. Equipment containing only resistive loads without any automatic switching device;
e.g. simple domestic heaters with no controls, thermostat, or fan；
3. Batteries and accumulators (without active electronic circuits)；
4. Headphones, loudspeakers without amplification；
5. Pocket lamps without active electronic circuits；
6. Protection equipment which only produces transitory disturbances of short duration
during the clearing of a shortcircuit fault or an abnormal situation in a circuit and
which do not include active electronic components, such as fuses and circuit breakers
without active electronic parts or active components;
7. High voltage types of equipment in which possible sources of disturbances are due
only to localised insulation stresses which may be the result of the ageing process and
are under the control of other technical measures included in nonEMC product standards,
and which do not include active electronic components；
8. 其他满足上面要求的设备或装置还有：
a) 电容器，如功率因素校正电容器；
b) 电磁感应马达；
c) 石英手表（无附加功能：如无线接收）；
d) 灯丝灯泡（钨丝灯泡）；
e) 不包含任何有源电子器件的家用开关；
f) 用于电视和无线广播接收；
g) 插头，插座，接线端子等。

同样，FCC认证也有类似之规定，在Part 15.103中称之为“Exempted devices”（豁免设备）。豁免设备包含：

1. A digital device utilized exclusively in any transportation vehicle including motor vehicles and aircraft.
2. A digital device used exclusively as an electronic control or power system utilized by a public utility or in an industrial plant. The term public utility includes equipment only to the extent that it is in a dedicated building or large room owned or leased by the utility and does not extend to equipment installed in a subscriber's facility.
3. A digital device used exclusively as industrial, commercial, or medical test equipment.
4. A digital device utilized exclusively in an appliance, e.g., microwave oven, dishwasher, clothes dryer, air conditioner (central or window), etc.
5. Specialized medical digital devices (generally used at the direction of or under the supervision of a licensed health care practitioner) whether used in a patient's home or a health care facility. Non-specialized medical devices, i.e., devices marketed through retail channels for use by the general public, are not exempted. This exemption also does not apply to digital devices used for record keeping or any purpose not directly connected with medical treatment.
6. Digital devices that have a power consumption not exceeding 6 nW.
7. Joystick controllers or similar devices, such as a mouse, used with digital devices but which contain only non-digital circuitry or a simple circuit to convert the signal to the format required (e.g., an integrated circuit for analog to digital conversion) are viewed as passive add-on devices, not themselves directly subject to the technical standards or the equipment authorization requirements.
8. Digital devices in which both the highest frequency generated and the highest frequency used are less than 1.705 MHz and which do not operate from the AC power lines or contain provisions for operation while connected to the AC power lines. Digital devices that include, or make provision for the use of, battery eliminators, AC adaptors or battery chargers which permit operation while charging or that connect to the AC power lines indirectly, obtaining their power through another device which is connected to the AC power lines, do not fall under this exemption.
9. Responsible parties should note that equipment containing more than one device is not exempt from the technical standards in this part unless all of the devices in the equipment meet the criteria for exemption. If only one of the included devices qualifies for exemption, the remainder of the equipment must comply with any applicable regulations. If a device performs more than one function and all of those functions do not meet the criteria for exemption, the device does not qualify for inclusion under the exemptions.
值得指出的是：豁免设备仍需符合part 15.5和part 15.29之一般规定。FCC如发现某一豁免设备可能引发有害干扰时，其使用者应停用该设备。直到干扰问题解决前，均不得再使用该设备。豁免设备虽非强制要求符合FCC part 15B的技术规定，但FCC依然建议此类设备制造商尽一切努力，以符合FCC part 15B的技术规定。

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哪些产品可以免除EMC测试？

同样，FCC认证也有类似之规定，在Part 15.103中称之为“Exempted devices”（豁免设备）。豁免设备包含：

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