IEC 60601-2-27: What does "linear within ±20% of the full scale output" mean?

S

smallbear

#1
I'm conducting tests per IEC 60601-2-27. I have a particular question regarding Clause 201.12.1.101.1, Accuracy of Signal Reproduction. The requirement is: "Input signals in the range of ±5 mV, varying at a rate up to 125 mV/s, shall be reproduced on the output with an error of ≤ ±20 % of the nominal value of the output or ±100 μV, whichever is greater."

The test is simple:
1. Set gain to 10mm/mV.
2. Input a triangular wave.
3. Adjust input signal amplitude to 100% full scale peak-to-valley output.
4. Decrease input signal amplitude by factors of 2, 5, and 10.

Success criteria:
For each signal amplitude in (4), the displayed output shall be linear within ±20 % or ± 100 μV of the full scale output.

My question is:
How do you interpret the success criteria? I'm assuming the +/-20% is allowing a margin of error for output signals that are not perfectly triangular, which means it's acceptable to have a noisy/distorted signals?

I'm currently interpreting this as a 20% linearity on a single test case. It's not making sense to me on how this 20% applies to the full scale output.

Any help would be greatly appreciated.

Thanks.
 
Elsmar Forum Sponsor

Eamon

Involved In Discussions
#3
I interpret this as follows. I welcome corrections from those more knowledgeable.

A triangle wave is a sequence of linear (straight-line) slopes. The output has to be linear and accurate as specified. As such, at no point must it depart from the nominal trace by a vertical amount of more than 20% of the full-scale output, or 100μV, whichever is greater.

This will cover nonlinearity as well as scaling (gain) errors. I agree it is a rather large allowance for nonlinearity, but this might be because for the most part they are testing the gain accuracy. (If lots of nonlinearity appears while doing the test, the designer will probably want to fix it even if it technically doesn't fail.)

I don't have the standard in front of me, but while excessive noise could conceivably cause a deviation that would make this test fail, isn't there a separate requirement for noise that would probably end up being stricter than this one as far as noise is concerned?

Eamon
 
S

smallbear

#4
Eamon,

Thanks for your input. It sounds like the margin of error for linearity is computed once at full scale output (i.e. 20% of full scale output), and then applied to subsequent test cases where the input signal is decreased. I've outlined this in the attached photo. Would you agree?

In our case, our full scale output isn't linear to begin with (i.e. slightly curved due to RC filtering), but I could imagine this criteria can still apply.
 

Attachments

Eamon

Involved In Discussions
#5
Hi smallbear,

I can't claim to be an expert, and I don't have the test in front of me, but to me, it is kind of common sense that unless another meaning is made explicit, "full scale" is to be taken in the context of each measurement being made.

That's what it means, for example, when you are talking about an oscilloscope screen. It's pretty clear that percent of full scale at 5mV / division is not referenced to what it would be at the scope's least sensitive setting, say 50V / division.

Linearity is typically more of a problem the bigger the input signal. According to what you've reproduced of the test sequence, the greatest amplitude is covered first. Unless there is some weird stuff going on (like for example distortion where the signal crosses through zero) there shouldn't be any problem meeting the accuracy and linearity requirements at lower levels, even if the error threshold needs to be considered to scale down with the signal.

To put it a bit differently, equipment that fails linearity at low levels but passes at higher levels may have some issues that need looking into.

Eamon
 

Peter Selvey

Leader
Super Moderator
#7
This is one of the tests which has been around for years since articulated arm type ECGs which could potentially have a lot of distortion due to the mechanical aspects of the system.

Although IEC 60601-2-27 first included performance tests in the 2005 edition, many of the test are derived from much older ECG standard such as OIML R90 (1990) and very old national standards in US, China etc.

The original test in the 2005 edition started at 10% and then increased up to 100%, which makes sense if you think about it from a mechanical system point of view, i.e. start at 10% full scale, ramp it up to 100% and see what the error is and make sure it is within ±20% - a relaxed limit appropriate for mechanical systems from 1897.

But does not make sense for modern ECGs with 40mm dot matrix thermal printer strip since starting at 10% is only 4mm and trying to adjust that is quite difficult.

So in the 2011 edition they changed to starting at 100% and working down to 10%. That actually makes the test much easier to pass, and combined with the far higher accuracy in modern digital ECGs, will leave more than one test engineer scratching their head as to what the ?? is this test all about.

As a side note, I have noticed some modern ECGs seem to exhibit something like op-amp slew rate limitation (which may come from high gain low noise op-amps, struggling to drive capacitors in the high pass filters) and occasionally compression around the rail voltage. So, non-linearity can still be a problem. But the tests in the standard don't seem to really designed around the issues for modern electronics.
 
Last edited:
Thread starter Similar threads Forum Replies Date
XRAY_3121 Class II heating pad - does the power supply have to have IEC 60601-1 testing?? US Medical Device Regulations 5
M How does IEC-60601-1 apply to a non-medical device in the patient vicinity? IEC 60601 - Medical Electrical Equipment Safety Standards Series 1
shimonv IEC 60601-1-8 - When does an error message become an alarm signal? IEC 60601 - Medical Electrical Equipment Safety Standards Series 14
MDD_QNA IEC 60601-1 Ed2 vs Ed3 - Does a product that conforms to Ed3 also fulfill Ed2? IEC 60601 - Medical Electrical Equipment Safety Standards Series 2
E What does "other APPLIED PARTS" mean in IEC 60601-1 ed 3.0 8.7.4.7 b) IEC 60601 - Medical Electrical Equipment Safety Standards Series 5
R Does long-term body worn medical monitoring device need to meet IEC 60601-1-11? IEC 60601 - Medical Electrical Equipment Safety Standards Series 4
S IEC 60601-1 3rd Gap analysis template TO BUY - Does anyone know where? IEC 60601 - Medical Electrical Equipment Safety Standards Series 2
D Will buyers (hospitals) require IEC 60601, even when FDA does not? IEC 60601 - Medical Electrical Equipment Safety Standards Series 5
R Does the Banana connector deviate from the IEC 60601-2-25? IEC 60601 - Medical Electrical Equipment Safety Standards Series 4
C Does IEC 60601-2-49 apply to Thoracic Bioimpedance? IEC 60601 - Medical Electrical Equipment Safety Standards Series 2
S Does a 12V DC device need EMC (IEC 60601-1-2) Testing? IEC 60601 - Medical Electrical Equipment Safety Standards Series 4
A Does Canade recognize IEC 60601-2-22? IEC 60601 - Medical Electrical Equipment Safety Standards Series 3
F IEC 60601-2-54:2009 Accuracy of CURRENT TIME PRODUCT IEC 60601 - Medical Electrical Equipment Safety Standards Series 2
C Sample qualification to be IEC 60601-1 series tested IEC 60601 - Medical Electrical Equipment Safety Standards Series 2
H Is testing according to IEC 60601-1 & IEC 60601-1-2 mandatory for a device being registered under MDR? IEC 60601 - Medical Electrical Equipment Safety Standards Series 4
G History of IEC 60601-1:2005 IEC 60601 - Medical Electrical Equipment Safety Standards Series 3
J IEC 60601-1-2 IEC 60601 - Medical Electrical Equipment Safety Standards Series 2
J IEC 60601-1 Clause 7.9.3.1 IEC 60601 - Medical Electrical Equipment Safety Standards Series 4
S Safety testing IEC 60601 series Medical Device and FDA Regulations and Standards News 2
F Battery overload in IEC 60601-1 vs 62133-2 IEC 60601 - Medical Electrical Equipment Safety Standards Series 3
S Mandatory tests for IEC 60601-1 IEC 60601 - Medical Electrical Equipment Safety Standards Series 11
D IEC 60601-1-2: Is EMC immunity testing required for a device without essential performance? IEC 60601 - Medical Electrical Equipment Safety Standards Series 25
E Clause 8.9.1.2 of AMD2:2020 of IEC 60601-1 IEC 60601 - Medical Electrical Equipment Safety Standards Series 1
P IEC 60601-1-2 RF wireless technology IEC 60601 - Medical Electrical Equipment Safety Standards Series 1
A IEC 60601-2-8 cl.201.10.1.2.101 and cl.201.10.1.2.104 IEC 60601 - Medical Electrical Equipment Safety Standards Series 0
G Risk Management for IEC 60601-1 and IEC 60601-1-2 IEC 60601 - Medical Electrical Equipment Safety Standards Series 15
J IEC 60601 Applied Part - Probes intended to be covered by sheaths IEC 60601 - Medical Electrical Equipment Safety Standards Series 3
S IEC 60601-1-11 Requirements related to Storage and Distribution IEC 60601 - Medical Electrical Equipment Safety Standards Series 6
shimonv IEC 60601-1-2:2014+A1:2020 (Ed. 4.1) IEC 60601 - Medical Electrical Equipment Safety Standards Series 5
G IEC 60601 Compliance IEC 60601 - Medical Electrical Equipment Safety Standards Series 2
W IEC 60601-1 clause 8.8.3 - Dielectric Strength IEC 60601 - Medical Electrical Equipment Safety Standards Series 8
B IEC 60601-1 Clause 14.8 - Architecture IEC 60601 - Medical Electrical Equipment Safety Standards Series 5
R IEC 60601-2-57 light source classification IEC 60601 - Medical Electrical Equipment Safety Standards Series 0
L Top opening of enclsoure against fire in IEC 60601-1 IEC 60601 - Medical Electrical Equipment Safety Standards Series 5
C EN 45502 vs IEC 60601-1-8 Other Medical Device Related Standards 0
JoCam IEC 60601-1 and 60601-1-2 retest after PCBA change IEC 60601 - Medical Electrical Equipment Safety Standards Series 3
K IEC 60601-1:2005/AMD2:2020, Why this standard version is 3.0? IEC 60601 - Medical Electrical Equipment Safety Standards Series 2
C IEC 60601 - 8.8.3 Dielectric Strength test. 4kv being applied to the ground conductor?! IEC 60601 - Medical Electrical Equipment Safety Standards Series 2
R IEC 60601-1 Clause 15.3.2, Push test IEC 60601 - Medical Electrical Equipment Safety Standards Series 0
A Defining a lower ESD test level in IEC 60601 safety test IEC 60601 - Medical Electrical Equipment Safety Standards Series 5
J IEC 60601-1-11 Home Class II With Ballasts IEC 60601 - Medical Electrical Equipment Safety Standards Series 3
A Coverage and differences: EN 60601-1:2006+A12:2014 Vs AAMI/IEC 60601-1:2005+AMD1:2012 IEC 60601 - Medical Electrical Equipment Safety Standards Series 2
T IEC 60601-1-8:2020 Is it necessary to change the alarm melody? IEC 60601 - Medical Electrical Equipment Safety Standards Series 5
M Is it normal / sufficient to have only the IEC 60601-1-2 test report without indicating IEC 60601-1? IEC 60601 - Medical Electrical Equipment Safety Standards Series 2
S IEC 60601-2-30 - Is it mandatory to claim alarms? IEC 60601 - Medical Electrical Equipment Safety Standards Series 1
Y Auditory alarm standard IEC 60601-1-8 Reliability Analysis - Predictions, Testing and Standards 0
R IEC 60601-1 - Power Supply Cords (Section 8.11.3.1) IEC 60601 - Medical Electrical Equipment Safety Standards Series 2
A Outsourcing IEC 60601-1 Ed 3.2 Testing IEC 60601 - Medical Electrical Equipment Safety Standards Series 0
R Complex IEC 60601-1 gap assessment IEC 60601 - Medical Electrical Equipment Safety Standards Series 0
D SINGLE FAULT CONDITION, short circuit and open circuit of any component (IEC 60601-1 3.1) IEC 60601 - Medical Electrical Equipment Safety Standards Series 9

Similar threads

Top Bottom