Leakage current is the current that flows from the unit through the grounding conductor into a household ground. Leakage current could shock an individual if the household grounding is not sufficient or there is an intentional or unintentional interruption of grounding connection.
Leakage current of 3 milliamps through the heart would create a mild shock and some pain ; 8 milliamps would cause an interruption in heart function (cardiac arrhythmia) which could eventually kill a healthy person in seconds.
Note: the requirement for medical equipment however is more stringent; a fatal shock could result if the patient is in a weak or unconscious condition.
CLASS I EQUIPMENT: Equipment where protection against electric shock is achieved with the combination of basic insulation and protective earth ground connect to case.
CLASS II EQUIPMENT: Due to the fact that there is no protective earth ground in the equipment, the protection against electric shock relies on double insulation or reinforced insulation.
CLASS III EQUIPMENT: Equipment in which protection relies upon supply source from SELV circuits and in which hazardous voltages are not generated.
PATIENT AUXILIARY CURRENT: Current flowing in the patient in normal use between parts of the applied part and not intended to produce a physiological effect; for example, bias current of an amplifier or current used in impedance plethysmography.
PATIENT LEAKAGE CURRENT: Current flowing from the applied part via the patient to the ground or flowing from the patient via an F-type applied partially to the ground, originating for the unintended appearance of a voltage from an external source on the patient.
For Information Technology Equipment (I.T.E.)
Classification - Maximum Leakage Current
Class I - 0.75mA (Hand held equipment) & 3.5mA (All others)
Class II - 0.25mA
For Medical Equipment
Current - Normal Condition - Single Fault Condition
Earth Leakage Current - 0.5mA - 1mA
Other than the medical leakage current requirement mentioned above, there are other leakage current requirements in IEC 601-1(Medical), such as patient leakage current, patient auxiliary current and enclosure leakage current. (We will not discuss these topics as they do not apply to our power supplies.)
For Class 2 Equipment
Type of Equipment - Maximum Leakage Current
Portable Unit - 0.5mA
Stationary Unit - 0.75mA
LED Wiki: Wi-Fi, Zigbee and Bluetooth compared
Key characteristics of ZigBee, Wi-Fi and Bluetooth
|Range||10-100 meters||50-100 meters||10 – 100 meters|
|Networking Topology||Ad-hoc, peer to peer, star, or mesh||Point to hub||Ad-hoc, very small networks|
|Operating Frequency||868 MHz (Europe) 900-928 MHz (NA), 2.4 GHz (worldwide)||2.4 and 5 GHz||2.4 GHz|
|Complexity (Device and application impact)||Low||High||High|
|Power Consumption (Battery option and life)||Very low (low power is a design goal)||High||Medium|
|Security||128 AES plus application layer security|| ||64 and 128 bit encryption|
|Typical Applications||Industrial control and monitoring, sensor networks, building automation, home control and automation, toys, games||Wireless LAN connectivity, broadband Internet access||Wireless connectivity between devices such as phones, PDA, laptops, headsets|
— Wi-Fi, Zigbee and Bluetooth comp...