What is Leakage Current?
 

The current is brimmed over as flowing through insulation impedance we called it leakage current, contact by human body and the current through human body flow to Earth then electrical damage is occurred. The difference between leakage current test, withstanding voltage test and grounding protection test is equipment testing under running status. The leakage current adds a human body simulation impedance circuit in testing, it can simulate the quantity of leakage current through human body under real condition.

How many types of leakage current tests are in the standards?
 

The leakage current with different test mode by various safeties and different leakage current standard by various test point. The most often seen is that the current flows through DUT (Device Under test)to E terminal of power, the human body touches E terminal of product will cause induction we called it earth leakage current. When earth leakage current is testing input 110% rated voltage to add human simulation circuit and judge if the current value of flowing through human simulation circuit is over the limit value of leakage current. In addition, there are Patient Leakage Current, Patient Auxiliary Leakage Current and etc leakage tests.

Why are leakage current tests so important in Medical Equipment Safety Standards?
 

The definition of medical equipment is the physical or electrical contact with patients (mostly regulations denotes human being, Europe regulations denotes human being and animal), applies to the equipment of diagnosing, treating and monitoring. The leakage current testing of medical equipment emphasizes on Applied part under normal using status by physical method to contact patient or accessories and facilities the patients need to touch such as probe, electrocardiogram, blood pressure bar and operating table. All types of leakage current will cause electrical hazards to patients and operators.

What is earth leakage current?
 

The current flows from the power terminal through DUT to E terminal of power as product running.

What are the different types of insulation? (Class I, II, III)
 

Whatever national standard regulation or region standard regulation, the standard of leakage current is different by the insulation types of products. “CLASSI, II, III” are mainly in consideration of the insulation system of product which derived from IEC system, brief descriptions are as below: CLASS I indicates anti-shock protection of product not only depends on basic insulation but also includes grounding method. CLASS II indicates anti-shock protection of product not only depends on basic insulation but also includes additional precaution. For example double or reinforce insulation but without grounding or installation condition for relying precaution. CLASS III indicates anti-shock protection of product depends on power voltage is safety extra-low voltage (SELV) and it don’t generate danger.

What is Enclosure / touch Leakage Current?

The current flow from two kinds of power terminal through DUT to accessible part of chassis, touch point and screw products, created inductance as human body touch, we called it enclosure/touch/chassis leakage current.

What is patient leakage current?
 

Patient leakage current consists of three kinds of test. The first test is the current flow from power terminal through applied part to earth terminal as product operating;Another test of patient leakage current, power source applies to MD by 110% the highest operating voltage. Make the current flows through applied part, accessible part then to earth terminal;The third test of patient leakage current, power source applies to SOP/SIP by 110% the highest operating voltage. When the product is operating, the current flows from two kinds of power terminal through applied part, MD then to earth terminal.

What is Patient Auxiliary Leakage Current?
 

When the product is operating, the current flows from test point of applied part through MD to another test point of applied part then to earth terminal.

 

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Useful links

IEC 60601-1 Prodcut Safety Compliance testing

Leakage-Current Testing for Patient-Monitoring Devices

     Understanding the most common electrical safety test requirements

What is Chassis Leakage Current ?

     Recommendations for Safe Current Limits for Electrocardiographs

     Safety in the health care facility

AAMI Consultants (safety) Directory

AAMI Standards (new)

AAMI Standards Publications

AAMI Certification

AAMI Standards program  Degradation aspects related to biological testing

AAMI Standards   General requirements for basic electrical safety

Equipment evaluation form - Saint Thomas Health Services

Medical Equipment mangement Plan