IEC Standards for the Safety and. Efficacy of Medical Electrical Equipment . Introduction. It might, perhaps, be a little too self-evident to say that there is no. to IEc Biomed testing on the move. If you need it with you on-site, the Med -eKit Test Trolley will carry it. The Rigel Med-eKit is huge on technical features. with IEC World's smallest, automatic, electrical Contents Innovating Together. safety analyser Foreword 2 8 IEC Leakage Measurements.
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Insulation Resistance Applied Parts to Mains. 8. IEC Leakage Measurements. Method Characteristics. Direct Leakage Provides. In-Service Test Requirements. 4 Introduction to IEC How does IEC compare. 13 with IEC ? Technical Considerations. STANDARD. IEC. CEI. NORME. INTERNATIONALE. First edition. Première édition. Medical electrical equipment –. Recurrent test and test after.
An Introduction to IEC Published on September 7, The requirement for safety testing medical electronic ME equipment is regarded as essential to ensure that apparatus does not pose any danger to users or patients. To meet this need, many different standards have been published to describe what is considered safe for the patients and operators of ME equipment. The most widely used standard is IEC Clearly, safety testing at the design stage and at the end of the production line are vitally important, but what about when the equipment enters service? This was the basis for the introduction of IEC , the newly published international standard for medical electrical equipment—recurrent test and test after repair of ME equipment.
As far as possible, it is an attempt at standardizing the safe operation and testing of ME equipment, while respecting specific local requirements and meeting increasing demands for risk management. In meeting these aims, IEC incorporates tests beyond those of type testing. Specifically, it seeks to provide a uniform and unambiguous means of assessing the safety of medical equipment, while maintaining the relation to IEC , and minimizing the risks to the person conducting the assessment.
Importantly, the new standard recognizes that the laboratory conditions described in IEC cannot always be guaranteed when in-service testing of medical devices is undertaken. In-Service Test Requirements As a type-testing standard, the current IEC does not provide any guidance to standardizing test requirements once an item of ME equipment has passed the design phase.
Once a medical device enters into service, a number of potential test scenarios arise, including: Acceptance testing, also referred to as initial or reference testing. This test is carried out before a new medical device is authorized for use, and is undertaken to ensure correct and complete delivery.
Acceptance testing is often not limited to electrical safety tests, with some basic function tests being applied to verify correct performance. Routine testing, also referred to as PPM, preventive product maintenance.
Routine testing is not limited to safety testing and often includes the verification of correct functionality. After service and repair testing—carried out following a repair, adaptation, or product upgrade. It is often part of a service carried out by in-hospital mechanical or clinical engineering teams. In many cases, more rigorous electrical safety testing is needed after the replacement of components or reconfiguration of medical devices. Although visual inspection is not clearly defined in IEC , its inclusion is a fundamental requirement of all routine test and maintenance procedures.
The following are typical visual checks that should be made: Housing enclosure—look for damage, cracks, etc; Contamination—look for obstruction of moving parts, connector pins, etc; Cabling supply, applied parts, etc —look for cuts, wrong connections, etc; Fuse rating—check correct values after replacement; Markings and labeling—check the integrity of safety markings; and Integrity of mechanical parts—check for any obstructions. Three different insulation test methods are recommended for different types of ME equipment.
The test methods are: Insulation between mains parts and ground—this test is used to verify that the mains parts are adequately insulated from ground Class I or the enclosure Class II. Insulation between applied parts and ground—this test is used to verify that the applied parts are adequately insulated from ground Class I or the enclosure Class II. Insulation between applied part and mains—this test is used to verify that the applied parts are adequately insulated from the mains parts and is applicable to Class I and Class II BF and CF equipment only.
IEC Ground Bond Test The ground bond test proves the integrity of the low-resistance connection between the ground conductor and any metal conductive parts, which may become live in fault situations with Class I medical devices.
Although many Class I medical devices are supplied with an equipotential point, most, if not all, medical devices require multiple ground bond tests to validate the connections of additional metal accessible parts on the enclosure. IEC requires a minimum test current of mA, either AC or DC, but when using a DC test current, the resistance must be tested in both polarities of the test current. The open circuit voltage of the current source should not exceed 24V.
The highest test reading will determine the pass or fail result of this test in comparison with different test limits included in IEC for different types of equipment. For example, the test limit for a Class I device including a power cable not exceeding 3 meters is mV. Higher test currents of 25A or 10A have been traditionally favored, based largely on IEC requirements.
The assumption was made that higher currents could best detect any damaged conductors present. In addition, when analog instruments were widely used for low-resistance measurement, it was often necessary to use high-test currents to produce sufficient voltage drop across the sample to generate the necessary needle deflection. However, higher test currents—of 10A or more—might potentially be destructive to parts of the device under test, which are connected to the protective ground but have a functional purpose, such as screening.
As such, consideration should be given to the test current. With modern electronics and digital technology, the use of higher test currents is regarded as no longer necessary—a fact recognized by IEC with its mA minimum current. On the other hand, low-test currents—of less than 8A—may not always overcome problems associated with contact resistance caused by constriction, pressure, or film resistance factors, and may therefore show a relatively higher reading than there is and indicate unnecessary failures.
Recently, new test technology has been pioneered in the form of a new low-energy, high-current test that overcomes the previous contact-resistance problems that inhibited the wider application of protective ground testing using 1A or mA test currents.
Importantly, the new low-current test technology enables valid ground continuity tests to be carried out using battery-powered testers, significantly increasing the portability and versatility of handheld safety analyzers used in in-service safety testing routines, significantly speeding up the testing process. IEC Leakage Testing Research has shown that it is current rather than voltage that is the source of electricity-related injuries and deaths. As a result, there are stringent rules on the design of medical equipment to ensure that the patient and operator are not exposed to those currents that do not form part of the functional operation of the device.
These are called leakage currents. In the interests of helping to guarantee safer practice and the repeatability of test measurements, IEC defines different types of leakage current tests—one for total equipment leakage and another for applied parts leakage currents.
IEC specifies three methods— direct, differential, and alternative—that can be used to determine the leakage of EM equipment.
Direct Leakage Method The direct leakage method included in IEC is the same as that in IEC , measuring the true leakage through a body model measuring device to ground. Another disadvantage is that secondary ground connections will produce a lower reading, thus potentially allowing faulty equipment to pass the test. The direct method does therefore require a fully isolated device under test and must be performed on a terre neutral supply and in each polarity of the incoming mains supply to guarantee measurements are taken at the maximum potential leakage current.
Keeping It Safe Follow this checklist for safety testing and keep all the bases covered. This can be done by wrapping the enclosure in aluminium foil and connecting to the auxiliary lead via an alligator clip. The methods of testing insulation are separated into: See definition of Enclosure Class II.
Higher Test Currents overcome the contact resistance where lower currents show a relatively higher reading. Figure 4 show a representation of the Applied Parts to Mains Insulation test. Insulation test. During this test.
BF and CF equipment only. Figure 3A: This test is applicable to enclosure of the equipment. Current flowing through directly to death a person to earth from the Applied Part or current flowing from a person to Earth via the These small amount of current to cause major currents are referred to as leakage currents. The result of be tolerated over 15 minutes imbalance in current between the Live conductor and the Neutral conductor Compare these values to the fact that mA of The Direct Leakage Method is identical to the current is required to power a 25 watt lamp.
It takes only a the functional operation of the device. Current flowing down the 0. Enclosure and Mains Parts combined to real Earth For example.
Any voltage leakage current between Neutral and Earth might result in a lower reading.
Protective Earth Conductor. Alternative method currents on equipment with switched circuits The Alternative Method is similar to a Dielectric Strength Test at mains potential.
IEC electrical equipment for measurement. These measurement circuits are measuring voltage is dependent on the test load. As such. BF and CF equipment. Class I EUT interrupted. Measurements are done in both polarities of the MD incoming mains with the protective Earth to the Figure 5A: Equipment Leakage Direct. The Figure 6A: The MD is part of a differential current measurement between the Live and Neutral conductors.
The Differential Leakage method is Potential secondary Earth connections are unsuitable for measuring conductive Un-Earthed included in the total measurement and the DUT parts and in those instances where leakages are is not required to be isolated from Earth. N L Unlike the Direct Method. M The test is conducted with the protective Earth connection closed for protection of the user.
Figure 7A: Figures 7A As Live and Neutral are shortened. Equipment Leakage Alternative method The test is performed using current limited This method is in fact similar to a dielectric test 3. All Applied Parts. Earthed e. MD Figure 7B: The test is conducted by applying a current limited 3.
Applied Parts and Patient Connections not part of the measurement shall be left floating i. N L AP2 Warning: Figure 8A: Both sources depend on a current limiting resistor which Figure 8B: Alternative Method. Figure 9A: MD Figure 9B: AP2 The test is conducted with the protective Earth connection closed for the protection of the user.
Once By doing so. To ensure patient monitors are displaying the correct readings. Temperature Simulator. ECG Simulator. Ventilator Tester. The IEC provides a guideline in collecting such information with the purpose of developing Electrical safety testing is only part of the total consistency in data collection and management. Infusion Pump Tester etc. Ensure that contact resistance is taken into The IEC standard will provide.
Ensure that the operator of the safety test www. Please visit our website 1. When determining the correct means of analyser. Ensure that Leakage Measurements are performed whilst the equipment is in full operation mode. Ensure high accuracy and repeatability of leakage measurement readings some Electrical safety testing of medical electronic manufacturers might specify full scale devices remains a crucial part of the overall accuracy which will affect the accuracy of low safety validation of medical devices and requires leakage measurements specialised test equipment.
Live components. The network and voltage measuring instrument above is replaced by the symbol MD in the following figures. For a list of particular standards. In such a case the manufacturer should give information in accompanying documents. NOTE 2: Particular standards may allow different values of leakage current. This IEC standard does not provide measuring methods and allowable values for equipment producing DC leakage currents.
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