Routine testing of medical electrical systems - What specific electrical safety tests should be performed?

Michael Ayers

Starting to get Involved
#1
Hi everybody. I'm new to this forum and would really appreciate any help with regards to the following. If we are using IEC 60601 as a basis for routine testing of medical electrical systems, what specific electrical safety tests should be performed?

From Clause 16 of 60601, I can find reference to these tests:

- protective earth resistance (16.9.2.2)
- earth leakage in normal condition (16.6.2)
- touch current in normal condition and with earth disconnected (16.6.1)
- patient leakage testing in normal condition (16.6.3)

If it is assumed that all relevant parts of the system have already been tested to 60601 at an equipment level, what other tests should we be doing to ensure the system is safe?

- Insulation testing?
- Measuring voltage on accessible parts?
- Patient auxiliary current?
- Mains on applied parts?

Also, why is the touch current test the only test where singe fault condition testing is required (and then only with earth conductor disconnection, not neutral conductor disconnection)?

Many thanks for any help.

Michael
 
Last edited:
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Ahang

Registered
#2
Hi everybody. I'm new to this forum and would really appreciate any help with regards to the following. If we are using IEC 60601 as a basis for routine testing of medical electrical systems, what specific electrical safety tests should be performed?

From Clause 16 of 60601, I can find reference to these tests:

- protective earth resistance (16.9.2.2)
- earth leakage in normal condition (16.6.2)
- touch current in normal condition and with earth disconnected (16.6.1)
- patient leakage testing in normal condition (16.6.3)

If it is assumed that all relevant parts of the system have already been tested to 60601 at an equipment level, what other tests should we be doing to ensure the system is safe?

- Insulation testing?
- Measuring voltage on accessible parts?
- Patient auxiliary current?
- Mains on applied parts?

Also, why is the touch current test the only test where singe fault condition testing is required (and then only with earth conductor disconnection, not neutral conductor disconnection)?

Many thanks for any help.

Michael
Hello Michael,

- Answer to your first question:
As stated in sub-clause 16.1,
1- you should first specify that which part(s) of your me system is(are) installed in the patient environment and which is(are) outside of this environment.
2- For those parts which are in the patient environment whether they are medical devices or non-medical devices (e.g. a laptop connected to the medical device in order to extract data), all me equipment relevant requirements shall be applied according to 60601-1 (e.g. all parts of clause 8).
3- For those parts which are not in the patient environment, their related safety standards shall be applied.
As an example imagine that you connect an active medical device (which is connected to the patient) through a network to a monitor in the nurse station, in this case, the medical device is in the patient environment and shall be tested according all applicable requirements of IEC 60601-1. But the monitor is outside of the patient environment and shall be in compliance with ITE safety standards (e.g. IEC 60950)

Answer to your 2'nd question:
Refer to IEC 60601-1, 8.7.1 b) 3’rd dash, all leakage currents including touch current shall be measured in both normal condition and single fault condition.

Ahang Rabiee
 

swathi.sp

Starting to get Involved
#3
Dear Folks,

Further to Leakage current test as per IEC 60601-1 , Clause 8.7, we have our own designed human body impedence circuit "as illustrated below representead as "MD in 60601-1. Can anybody help me to understand how to analyse the frequency characteristics of the Measuring device.



1568107273602.png
 

Benjamin Weber

Trusted Information Resource
#5
Dear Folks,

Further to Leakage current test as per IEC 60601-1 , Clause 8.7, we have our own designed human body impedence circuit "as illustrated below representead as "MD in 60601-1. Can anybody help me to understand how to analyse the frequency characteristics of the Measuring device.



View attachment 26052
Well, actually frequency analysis comes for free here. Just look at the right figure, that is the frequency response of the low pass filter / measuring device in the left.

It is a simple first order low-pass with a cut-off frequency of 1061 Hz (-3db, defined by R1 and C1). The resistor R2 is the shunt resistor through which the leakage current is flowing.

More Info:
Low-pass filter - Wikipedia -> Electronic low-pass filter
 

swathi.sp

Starting to get Involved
#6
Well, actually frequency analysis comes for free here. Just look at the right figure, that is the frequency response of the low pass filter / measuring device in the left.

It is a simple first order low-pass with a cut-off frequency of 1061 Hz (-3db, defined by R1 and C1). The resistor R2 is the shunt resistor through which the leakage current is flowing.

More Info:
Low-pass filter - Wikipedia -> Electronic low-pass filter
Many thanks Benjamin. Your response is so helpful for me to understand further.
 
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