Glossary of Technical Terms used in Electromedical Metrology

CONTENTS

- Introduction

- Related Standards

- Terms and Explanations

- List of Symbols

- List of Abbreviations

- List of Figures

- List of References

INTRODUCTION

In order to complete electrical safety measurements and tests on technical medical devices, it is essential to be familiar with technical terms used in various standards. Experience shows that students of medical engineering often have problems understanding and interpreting specific, technical terms.

A compilation of essential technical terms is also helpful with regard to the current modification of relevant (medical engineering) standards. The following lists should help to explain these terms in a comprehensible way (without resorting to the language used in official standards).

One basis for electrical safety tests performed on medical devices is the Medical Devices Directive (German MPG) and the resulting Medical Devices Operator Ordinance (German MPBetreibV).

The paragraphs of this Ordinance indicated below require, directly or indirectly, the completion of electrical safety measurements as well as maintenance and repair work:

- Medical Devices Operator Ordinance §2, Paragraph 8 [1]
(Regulations on recurrent tests, accident prevention regulations, safety-related inspections),
- Medical Devices Operator Ordinance §4, Paragraph 4 [1]
(Maintenance and repairs),
- Medical Devices Operator Ordinance §6, Paragraphs 1 and 3 [1] (Safety-related inspections, recognised rules of engineering, schedules, test reports),
- Medical Devices Operator Ordinance §7, Paragraph 4 [1]
(Test reports with results, tester).

The paragraphs stipulated oblige the operator of medical devices to have electrical safety tests and function tests completed on the devices regularly and according to schedule by applicably skilled personnel.

STANDARDS

The following standards are those whose priority, is basically concerned with the electrical safety of technical medical devices. Other associated standards, which apply to the general safety of all electrical devices and equipment, will not be elaborated on or further interpreted here.

Currently applicable standards concerning the electrical safety of medical devices are:

- DIN EN 60601 -1, current version dated August 2002 [2]

This standard describes the general definitions regarding the electrical safety of technical medical devices including the main performance features. This standard, can be considered the "basic standard" in respect of electrical medical devices. It provides support and is a basic source of reference during the development, production and testing of medical devices. This standard is the source of some of the following terms and explanations.

- DIN EN 62353, current version dated August 2008 [3]

This standard describes the testing of the electrical safety of technical medical devices following maintenance and repair.

The regular, recurrent electrical safety tests associated with the operation of a medical device are also described. This standard contains the measurement methods, test procedures and electrical parameters (limit values) which must be observed and maintained. This standard is the source of some of the following terms and explanations.

At this point, it is also worth mentioning DIN VDE 0701-0702 [4], the current version of which is dated June 2008. This standard is concerned with the general aspects of testing electrical devices following repair or modification. However, it is not specifically related to medical devices and, as a result, is not expanded upon further here.

TERMS AND EXPLANATIONS

The following terms and explanations are absolutely essential for understanding and completing electrical safety tests on medical devices properly:

- Protection Class 1

Protection Class 1 infers that in order to provide protection from dangerous electrical currents, namely from an electric shock, all conductive device parts which could come into contact with the human body must be connected to electrical earth. This connection ensures that the housing parts are always earthed and do not conduct electricity. This protection is provided automatically when the safety plug is inserted in the electrical socket (power supply). However, it must be ensured that all conductive device parts are connected with each other by a protective earth conductor (green / yellow). These connections are realised inside the device by means of earth cable and protective conductor contacts (screwed connections) on the individual, exposed conductive parts. Following repair or opening the device, pay attention that all PE connections are restored.

Abbildung in dieser Leseprobe nicht enthalten

Fig. 1

The figure illustrates an earthed power socket, a safety plug and realisation of Protection Class 1 in a medical device (HF heat therapy device)

TERMS AND EXPLANATIONS

- Protection Class 2

Protection Class 2 infers that devices classified according to this protection class must be provided with additional insulation (additional to the existing, basic insulation). This additional insulation ensures that, in the event the basic insulation fails, no electricity or voltage can flow through exposed housing parts. This is realised by an additional, double insulation of the device components conducting voltages and currents. Exposed parts (housing parts) of devices classified as Protection Class 2 are often made completely out of non-conductive plastics. No protective earth conductor (green / yellow) is connected in devices classified as Protection Class 2.

Abbildung in dieser Leseprobe nicht enthalten

Fig. 2

The figure illustrates a Protection Class 2 plug and a Protection Class 2 medical device (infusion pump) with applicable rating plate.

Further information on classification and application of protection classes is available in the standards EN 61140 [5], current version dated March 2007, and EN 50274 [6], current version dated November 2002. The standards describe the protection of systems and resources against electric shocks and protection against unintentional direct contact with hazardous live parts.

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