A Practical Guide for
Medical Equipment and
Electrical System Testing
According to International Standard:
IEC 62353: Medical electrical equipment – Recurrent test
and test after repair of medical electrical equipment
www.metrel.si
Introduction
Medical equipment testing is another sub-field of PAT
testing, but one that requires special care since the
tested devices are in direct contact with medical staff and
patients, which translates to a heightened probability of
electric shock.
There are numerous types of medical equipment that
needs to be regularly inspected and tested to maintain its
reliability. Metrel has developed a special version of MI 3360
OmegaPAT XA (model M), which covers the international
standard IEC/EN 62353 for medical electrical equipment
testing.
This guide covers a basic introduction to electrical safety,
basic definitions of a medical equipment (ME) and an
overview of the IEC 62353 standard.
The test diagrams presented in this booklet are designed
as a guideline for people involved in testing of medical
electrical equipment with the OmegaPAT XA MI 3360M.
The guide itself cannot replace the standard IEC 62353
which was used as a reference for preparation of this
booklet.
For clarification on any part of this guide, contact Metrel d.d.
Page 2
Table of contents
Classification of equipment (by protection classes) 4
Typical parts of a medical equipment 5
1. Visual check (Class I, II, III) 6
2. Earth bond (Class I) 7
3. Insulation resistance (Class I, II)
8-9
4. Leakage currents10
4.1 Measurement of equipment leakage current 11
4.1.1 Alternative method (Equipment leakage) 11
4.1.2 Direct method (Equipment leakage) 12
4.1.3 Differential method (Equipment leakage) 13
4.2 Measurement of applied part leakage current
14
4.2.1 Alternative method (Applied part)
15
4.2.2 Direct method (Applied part) 16
4.3 Measurement of touch leakage current Sequence of testing
Sequence for selection of appropriate leakage current
17
18
19
AUTO SEQUENCE®
20 - 22
Professional reporting
23
Page 3
Classification of equipment (by protection classes)
CLASSIFICATION OF EQUIPMENT (BY PROTECTION CLASSES)
Class
I
Marking
No
Supply cord
Three pole
(L, N, PE)
II
III
III
Two pole,
L, N
Two pole
Examples
CLASSIFICATION OF EQUIPMENT (BY PROTECTION CLASSES)
Type
B
B-body
Description
Equipment with applied part(s) not isolated from power supply and
enclosure.
BF
F-floating
Equipment with applied part(s) isolated from power supply and
enclosure. Higher protection degree.
CF
C-cardiac
Equipment intended for cardiac applications on the patient, is
isolated from power supply and enclosure. Highest protection degree.
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Mark
A Practical Guide for Medical Equipment and Electrical System Testing
Typical parts of a medical equipment
Typical parts of medical equipment that are relevant for electrical safety
are shown on the picture below:
Accessible conductive part
A part of medical equipment other than applied
part that can come in contact with the patient.
Applied part
An applied part is a probe or other part of
equipment that necessarily comes into physical
contact with the patient for the medical
equipment to perform its function. Applied part
of TYPE-CF provides a higher degree of protection
against electric shock than parts of TYPE-B and BF.
Mains part
Electronic circuit that is connected to the supply
mains. The mains part includes all conductive
parts that are not separated from the supply
mains by at least one means of protection.
1. Mains part
2. L,N,PE conductors (supply cord)
3. Accessible metal part
4. Enclosure
5. Applied part of TYPE-B
6. Applied part of TYPE-F (BF, CF)
Page 5
1. Visual check (Class I, II, III)
Items that we should pay special attention to:
• Safety related markings, labels and labelling have to be legible and complete;
• The integrity of mechanical parts;
• Any damage or contamination e.g. any evidence of spillage;
• Assess the relevant ACCESSORIES together with the ME EQUIPMENT or
ME SYSTEM (e.g. detachable or fixed POWER SUPPLY CORDS, patient leads,
tubing);
• The required documentation is available and reflects the current revision
and/or CONFIGURATION of the ME EQUIPMENT or ME SYSTEM;
• All fuses accessible from the outside are compliant with the data given by
the manufacturer;
• After testing, REPAIR or adjustment, check that the ME EQUIPMENT or
ME SYSTEM is restored to the conditions necessary for intended use before
being returned into service.
Figure 1 (Visual inspection - IEC/EN 62353)
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A Practical Guide for Medical Equipment and Electrical System Testing
2. Earth bond (Class I)
Measurements shall be performed using a measuring device able to deliver a current of at least 200 mA into 500 mΩ.
The open circuit voltage shall not exceed 24 V.Low current tests (up to 1 A) are recommended, as they can disclose bad contacts.
Note 1: For large cross section areas and shorter conductor lengths, higher test currents for the continuity test improve the repeatability of the test results.
Type
Description
ME equipment or an ME system with non-detachable
power supply cord - Figure 2
ME equipment or an ME system with detachable power
supply cord - Figure 2
< 300 mΩ
Permanently installed ME equipment - Figure 3
< 300 mΩ
ME system with a multiple socket-outlet
TN system without RCD < 300 mΩ
Installed RCD or IT system < 500 mΩ
Table 1
Figure 2 (Protective earth resistance, Class I)
ME equipment or system only < 200 mΩ
Supply cord only < 100 mΩ
Complete system with supply cord < 300 mΩ
Figure 3 (Protective earth resistance, Class I, permanently installed)
Page 7
3. Insulation resistance (Class I, II)
If there is any doubt about the insulation of ME equipment, the insulation resistance
measurement shall be considered in addition to the leakage current measurement.
Measurements of the insulation resistance shall be performed with a test voltage
of 500 V (D.C.). Test voltage not lower than 250 V D.C. may be used if overvoltage
protective devices are included in the test configuration. Test equipment shall
be disconnected from mains and all switches shall be in operating position (ON).
Keep in mind that insulation resistance test is not mandatory!
Minimum insulation resistance for ME equipment
Between mains part and protective earth for Class I
ME equipment - Figure 4
Class I Class II
≥ 2 MΩ -
Between mains part and (non-earthed) accessible conductive ≥ 7 MΩ ≥ 7 MΩ
parts for Class II ME equipment (optional Class I) - Figure 5
Between mains part and applied part TYPE-B which make
≥ 2 MΩ ≥ 7 MΩ
a patient connection and protective earth Class II ME
equipment (optional Class I) - Figure 7
Between mains part and applied part TYPE-F which make a
≥ 70 MΩ ≥ 70 MΩ
patient connection and protective earth Class II ME equipment
(optional Class I) - Figure 7
Between TYPE-F applied parts which make a patient
≥ 70 MΩ ≥ 70 MΩ
connection and protective earth for Class I or Class II
ME equipment - Figure 6, 8
Table 2
Figure 4 (Insulation resistance, Class I)
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A Practical Guide for Medical Equipment and Electrical System Testing
3. Insulation resistance (Class I, II)
Measuring conditions for insulation measurement between mains parts and applied parts:
- all applied parts TYPE-B shall be connected together during test
- all applied parts TYPE-F shall be connected together during test
Figure 5 (Insulation resistance, Class II)
Figure 6 (Insulation resistance, Isolated metal housing
against TYPE-F applied parts, Class I, II)
Figure 7 (Insulation resistance, Mains part against
applied parts, Class I, II)
Figure 8 (Insulation resistance, Protective earth against
TYPE-F applied parts, Class I)
Page 9
4. Leakage currents
Depending on the ME EQUIPMENT or ME SYSTEM one of the following methods of measuring the EQUIPMENT LEAKAGE
CURRENTS or the APPLIED PART LEAKAGE CURRENT may be used:
a) Alternative method,
b) Direct method,
c) Differential method,
d) Alternatively, touch method or patient method derived from IEC 60601-1 may be used.
Equipment under testing shall be measured in the operating conditions.
Current
Equipment leakage current – alternative method
for accessible conductive parts of Class I ME equipment - Figure 9
for accessible conductive parts of Class II ME equipment - Figure 10
Equipment leakage current – direct or differential method
for accessible conductive parts of Class I ME equipment - Figure 11, 13
for accessible conductive parts of Class II ME equipment - Figure 12, 14
Touch current (according to IEC 60601-1)
for accessible conductive parts
Applied part leakage current – alternative method (A.C.)
according to Figure 15, 16
Applied part leakage current – direct method (A.C.)
according to Figure 17, 18, 19
TYPE-B
TYPE-BF
TYPE-CF
1000 µA
500 µA
1000 µA
500 µA
1000 µA
500 µA
500 µA
100 µA
500 µA
100 µA
500 µA
100 µA
100 µA
100 µA
100 µA
5000 µA
50 µA
5000 µA
50 µA
Table 3
Note 1: This table does not provide allowable values for equipment producing D.C. leakage currents.
Note 2: Certain standards can allow different values of leakage current.
For example: Defibrillation paddles, TYPE-CF: Leakage current from applied part: 100 µA Mobile x-ray generators, equipment leakage current, alternative method:
5000 µA, direct or differential method: 2000 µA
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A Practical Guide for Medical Equipment and Electrical System Testing
4. Leakage currents
4.1 Measurement of equipment leakage current
This measurement is not applicable for equipment with an internal electrical power source.
4.1.1 Alternative method (Equipment leakage)
ME Equipment is separated from mains and the equipment leakage current is measured according to Figure 9, 10.
Note 1: Class I ME does not need to be isolated from PE during measurement.
Note 2: If the leakage current exceeds 1 mA, either direct or touch measurement shall be applied (allowable values in Table 3).
Figure 9 (Equipment leakage, Alternative, Class I)
Figure 10 (Equipment leakage, Alternative, Class II)
Page 11
4. Leakage currents
4.1.2 Direct method (Equipment leakage)
Measurements shall be performed at mains voltage, and in either position of the mains plug, if applicable, and according to
Figure 11, 12. If measurements in different positions of the MAINS PLUG are applicable, the higher value shall be documented.
Note 1: If the measuring equipment is supplied by an IT power system, erroneous measured values will result. During the measurement, except for the protective
earth conductor in the power supply cord, the equipment shall be isolated from earth. Otherwise the direct method is not applicable.
Note 2: An earth potential can be imported, for example, by external data lines.
Note 3: When measuring equipment leakage current of Class I ME equipment, test personnel or bystanders can be endangered by an interruption of the protective
earth connection.
Figure 11 (Equipment leakage, Direct, Class I)
Page 12
Figure 12 (Equipment leakage, Direct, Class II)
A Practical Guide for Medical Equipment and Electrical System Testing
4. Leakage currents
4.1.3 Differential method (Equipment leakage)
Measurements shall be performed at mains voltage, and in either position of the mains plug, if applicable, and according to
Figure 13, 14. If measurements in different positions of the mains plug are applicable, the higher value shall be documented.
Note: If the measuring equipment is supplied by an IT power system, erroneous measured values will result. When measuring small leakage currents, attention
shall be paid to information about limitations from the manufacturer of the measuring equipment. If the value of the differential method exceeds 0,5 mA for
Class I ME, either the direct method or the touch current measurement shall be applied (allowable values in Table 3).
Figure 13 (Equipment leakage, Differential, Class I)
Figure 14 (Equipment leakage, Differential, Class II)
Page 13
4. Leakage currents
4.2 Measurement of applied part leakage current
Measurement of the applied part leakage current shall be performed on
equipment. For TYPE-B applied parts usually no separate measurement
is necessary, measurements are encompassed in the equipment leakage
measurement.
•
•
•
For TYPE-B applied parts usually no separate measurement is
necessary, measurementsare encompassed in the equipment leakage
measurement.
Separate measurements of TYPE-B applied part are necessary only if
described by the manufacturer (check accompanying documents).
TYPE-F applied part leakage current shall be measured from all patient
connections of a single function of the applied part connected together
according to Figure 15, 16. Figure 17, 18 or Figure 19, or as described by the
manufacturer. Alternatively, for TYPE-CF applied parts measurement can
be made from each patient connection in turn.
When testing ME Equipment with multiple applied parts, connect them each
in turn and comply with the applicable limits in Table 3. Applied parts not part
of the measurement shall be floating.
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A Practical Guide for Medical Equipment and Electrical System Testing
4. Leakage currents
4.2.1 Alternative method (Applied part)
Measurement in ME equipment having an TYPE-F applied part shall be performed according to Figure 15, 16 for mains operated
ME equipment.
Figure 15 (Applied part leakage, Alternative, Class I)
Figure 16 (Applied part leakage, Alternative, Class II)
Page 15
4. Leakage currents
4.2.2 Direct method (Applied part)
Measurements shall be performed at mains voltage, in either position of
the mains plug, if applicable and according to Figure 17, 18, or according to
Figure 19 in ME equipment having an internal electrical power source.
Note: If the measuring equipment is supplied by an IT power system, erroneous measured
values will result.
Figure 17 (Applied part leakage,Direct, Class I)
Figure 18 (Applied part leakage, Direct, Class II)
Page 16
Figure 19 (Applied part leakage, Direct, Internal power source)
A Practical Guide for Medical Equipment and Electrical System Testing
4. Leakage currents
4.3 Measurement of touch leakage current
(Alternatively, touch method derived from IEC 60601-1 may be used.)
This measurement is only required on accessible conductive parts that are not protectively earthed. Measurements shall be performed
at mains voltage, and according to Figure 20, 21.
Figure 20 (Equipment touch leakage current, Class I)
Figure 21 (Equipment touch leakage current, Class II)
Page 17
Sequence of testing
Figure 22, contains a recommended sequence for performing the tests described
in the standard EN 62353.
START
Selection of the test
Visual INSPECTION
PROTECTIVE EARTH
RESISTANCE
Insulation resistance
(not mandatory)
Leakage current
Functional test
Reporting of results
Evaluation
Check and prepare
for normal use
Figure 22 (Sequence of testing)
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A Practical Guide for Medical Equipment and Electrical System Testing
Sequence for selection of appropriate leakage current
Figure 23 contains an example decision chart
to assist in determining which test method
to apply when measuring leakage currents on
non-permanently installed Class I & Class II
ME equipment.
Close mains part switches
EQUIPMENT LEAKAGE CURRENT
No
Electronic switched mains?
Yes
Yes
No
Class I?
Yes
Protective earth
resistance complies?
Repair
No
EQUIPMENT LEAKAGE CURRENT
- differential method (Figure 13, 14)
APPLIED PART LEAKAGE CURRENT
No
F-Type APPLIED PARTS?
Active circuitry?
Perform applicable
tests
Value exceeds Yes 1 mA?
No
Yes
Measure each
applied
part in turn with other
applied parts left
floating
Yes
Pass?
Equipment isolated from earth?
EQUIPMENT LEAKAGE CURRENT
- direct method (Figure 11, 12) or
- differential method (Figure 13, 14)
No
Yes
Insulation resistance
measurement
specified?
Yes
LEAKAGE CURRENT
according IEC 60601-1
Measurement of
leakage current
EQUIPMENT LEAKAGE CURRENT
alternative method (Figure 9, 10)
Repair
No
No
POLYPHASE EQUIPMENT LEAKAGE
current value exceeds the
limits of Table 3?
No
No
Close mains part switches
Yes
Switch on equipment
Yes
APPLIED PART LEAKAGE CURRENT
- direct method (Figure 17, 18) or
Equipment with AN INTERNAL ELECTRICAL
POWER SOURCE (Figure 19)
APPLIED PART LEAKAGE
CURRENT
- alternative method (Figure 16, 17)
DOCUMENTATION
Figure 23 (Sequence for selection of appropriate leakage current)
Page 19
AUTO SEQUENCE®
Automatized test procedures or shorter AUTO SEQUENCE®s are one of Metrel’s most recognized innovative feature for many
years. MI 3360 M OmegaPAT XA with colour touch screen in combination with Metrel Electrical Safety Manager Software,
shorter called MESM has placed this feature on a completely new level.
Figure 24 (Metrel Electrical Safety Manager - Auto Sequence editor)
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A Practical Guide for Medical Equipment and Electrical System Testing
AUTO SEQUENCE®
The MI 3360 OmegaPAT XA enables the user to select Metrel’s predefined AUTO SEQUENCE®s, developed for medical applications,
in accordance with IEC/EN 62353. In addition to these predefined sequences the users can create their own custom sequences, using
our MESM AUTO SEQUENCE® editor. This tool enables the creation of sequences including comments, wire diagrams, pictures and
custom visual or functional inspections. In addition to this feature, there are no limitations about the design of the sequence flow,
quantity of the used steps for specific test or quantity of the comments or pictures used.
Figure 25 (List of sequences by cryteria)
Figure 26 (Connection diagrams)
Page 21
AUTO SEQUENCE®
For a skilled user such custom-made AUTO SEQUENCE®s can reduce time for testing, and on the other hand for the unskilled user
can make testing easier by checking comments connection diagrams and flow of the test sequence.
Figure 27 (Basic Auto Sequences)
Figure 28 (Alternative Auto Sequences)
Figure 29 (List of applicable tests)
Figure 30 (Selection of multiple points)
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A Practical Guide for Medical Equipment and Electrical System Testing
Professional reporting
Measurements are given in appropriate measuring reports / records with a tabular representation of results as may be seen in the
example of sample measurements down below.
Figure 31 (Detailed test information)
Figure 32 (Complete test results)
Page 23
METREL d.d.
Measuring and Regulation Equipment Manufacturer
Ljubljanska 77, SI-1354 Horjul, Slovenia
T +386 (0)1 75 58 200, F +386 (0)1 75 49 226
metrel@metrel.si, www.metrel.si
Photographs in this catalogue may slightly differ from the instruments at the time of delivery.
Subject to technical change without notice.
A Practical Guide for Medical Equipment and Electrical System Testing _Ang_2021