For approval according to IEC EN 60601-1, TÜV will usually require an insulation diagram. If you search for the term "insulation diagram" in the basic standard 60601-1, you won't find it. This article will explain what the insulation diagram is and what it is used for.
What does EN 60601-1 contain regarding the insulation diagram?
A lot of information can be found in EN 60601-1 in the annexes:
- Appendix J with an overview of insulation distances
- Appendix K with simplified patient leakage current diagrams.
In addition, Chapter 8.8 contains many requirements for insulation and test voltages, while Chapter 8.9 contains the requirements for clearance and creepage distances.
However, the standard never defines in detail what the insulation diagram is.
So what is the isolation diagram and what does it contain?
An insulation diagram is a diagram that is similar in simplicity to a block diagram and in which the insulation distances are drawn. An example is the following insulation diagram for an ear thermometer:
The diagram should be simple and reduced to the essentials. Typically, a separate document is created that contains this diagram and also documents the relevant product requirements. These include:
- Requirements for the insulation distances
- Documentation of insulation distances
- Calculations for dielectric strength, maximum stresses
- Test voltages for dielectric strength
- Definitions of the application parts
- References to regulations used or exceptions as may be defined in the Special Specifications (60601-2-xx)
- Information about pollution level, operating altitude, further information about the operation
Many of the symbols and terms used have already been introduced in the article about Electrical safety in medical technology.
| Dipl.-Ing. Martin Bosch, shareholder, hardware developer E-mail: bosch@medtech-ingenieur.de Phone: +49 9131 691 241 |
|
Do you need support with the development of your medical device? We're happy to help! MEDtech Ingenieur GmbH offers hardware development, software development, systems engineering, mechanical development, and consulting services from a single source. Contact us. |
|
Who are the readers of the insulation diagram?
One should also consider the different reader groups of the isolation diagram:
1. Hardwaree-developer
Typically, the isolation diagram is created by a hardware developer. It can also be used to discuss technical implementation options with other developers of a complex product or system. This brings us to the next reader:
2. System architects
It helps system architects maintain an overview of insulation requirements. There are often different options for dimensioning and dividing the isolation distances. The insulation diagram allows you to explore these options and document decisions.
Particularly important for system developers: Medical electrical systems must also comply with all leakage current requirements!
3. Licensing authority
The insulation diagram serves as a basis for discussions about electrical safety with the approval authority and can be used early in the project to coordinate the design with the approval bodies. Some of the safety-relevant (often referred to as critical) components can be quickly defined this way. It also defines the test voltages and isolation distances required for approval at the latest.
After all, it is part of the CB report (at the latest then it will be requested by the TÜV).
This article was not about creating the insulation diagram; that topic will be covered in another article. Anyone interested in this topic is welcome to contact us by phone, email, or via our website.
Best regards
Martin Bosch