Obtaining the CE marking for an electronic device — Part 1

A manufacturer who wants to sell an electronic device in the European Economic Area is responsible for affirming the device’s compliance with the relevant EU legislation. The manufacturer puts the so-called “CE marking” on the device to declare compliance.

The “CE marking”

Interestingly, there’s no such thing as a “CE certification”. Instead, it’s the responsibility of the manufacturer (or the importer) to ensure that the device meets EU health, safety and environmental standards.

In this blog post, I will use an example (a digital video camera) to show the necessary steps before one can put the CE marking on an electronic device.

In addition to the standards for the CE marking, there are other standards that may be applicable, such as WEEE, which I’m not going to discuss here but which need to be considered as well.

The Product

Our product is a new digital video camera for astronomical observations. Each frame that the camera records is timestamped at the beginning and end of the exposure. The image stream is then sent to a host PC over USB3 and saved on an SSD disk.

Prototype of the astronomical video camera, back and front view

The video camera uses a GPS module as a very accurate time base. Exactly at the beginning of each second, the GPS module generates a short pulse.

To record astronomical events, the user runs a software on a laptop computer. In the software, the user can configure various aspects of the camera such as exposure time, gain, binning, black level and so on.

The astronomical video camera in use

One type of astronomical event where the camera will be used are occultations of stars by asteroids. If an asteroid crosses our line of sight to a star, the star is dimmed for a short moment. If several observers record the same event from different places on earth, it’s possible to reconstruct the orbital data and shape of the asteroid.

Shape model with measurements from various observers; calculation by Eric Frappa, IOTA-ES, data provided by the observers in the list at the right side of the image

The screenshot above is an example of asteroid (2) Pallas. Each horizontal line corresponds to a single light curve.

If you’d like to learn more about star occultations, you can visit the web page of the International Occultation Timing Association, https://occultations.org.

Six Steps to CE

The European Commission provides detailed information on how to get the CE marking for a new product. They list 6 steps on their web page:

1. Identify the applicable directive(s) and harmonised standards
2. Verify product specific requirements
3. Identify whether an independent conformity assessment (by a notified body) is necessary
4. Test the product and check its conformity
5. Draw up and keep available the required technical documentation
6. Affix the CE marking and draw up the EU Declaration of Conformity

Let’s follow these steps for our video camera.

1 — Identify the applicable directive(s) and harmonised standards

The first step is to determine the applicable standards. On the web site of the European Commission, we find a collection of standards, grouped by topic. For electronic devices, there are 5 standards that may be relevant:

• Electromagnetic compatibility (EMC)
• Equipment for explosive atmospheres (ATEX)
• Low Voltage (LVD)
• Radio Equipment (RED)
• Restriction of the use of certain hazardous substances (RoHS)

Each standard starts with the description of the scope of the standard, which tells us whether the standard is relevant for us or not.

ATEX deals with “potentially explosive atmospheres” and LVD applies to devices in the 50–1000V AC or 75–1500V DC voltage ranges, so we can ignore these two standards, but the other three are applicable, according to their scope definition:

• EMC
• RED (because of the GPS receiver and the external antenna)
• RoHS

The fact that RED applies has an interesting side-effect. In article 2 of the EMC directive, we can read:

1. This Directive shall apply to equipment as defined in Article 3.
2. This Directive shall not apply to:
   (a) equipment covered by Directive 1999/5/EC;
   …

Directive 1999/5/EC is the predecessor of the RED 2014/53/EU. What this means is that if the RED applies, the EMC directive doesn’t apply or more precisely, the RED actually includes requirements equal to those in the EMC.

To summarize, only RED and the RoHS directive are relevant for us.

2 — Verify product specific requirements

The RED and RoHS directives as a whole are applicable, but in detail, they contain various requirements that may or may not be applicable in our specific case.

For RED, the European Union has published the RED guide to support us with the requirements, which contains a long check list. Some interesting points from the check list:

• We need a “type or batch or serial number or other element” to identify the devices.
• We need to deliver instructions and safety information with the device. “These instructions shall also include information about the frequency bands and power used by the radio equipment.”

3 — Identify whether an independent conformity assessment is necessary

Each directive specifies whether an independent conformity assessment is necessary. Neither RED nor ROHS require a notified body for the assessment.

For example, RED specifies:

(29) The manufacturer, having detailed knowledge of the design and production process, is best placed to carry out the conformity assessment procedure. Conformity assessment should therefore remain solely the obligation of the manufacturer.

4 — Product Testing (and Fixing…)

How can we ensure that our product meets the requirements specified in the standards?

• For ROHS, we check that each component and module in the BOM is compliant. If we combine only ROHS-compliant components, the product should be compliant, too. Most vendors declare for their component if they’re ROHS compliant or not; usually, there are different part numbers for compliant and non-compliant parts. In addition, distributors also list for each component they sell whether it’s ROHS compliant. Usually there’s filter function so that you can filter out all non-compliant components.
• For RED, we need to measure the spurious radiated emissions and check if they’re within the limits. We also need to check how the product reacts to incoming radio signals.

We follow a simple approach to comply with RED:

• During the design phase, we take care to minimize spurious radiated emissions, e.g. by provide a return path for each signal line, for example by putting solid ground planes next to the signal lines or by using differential signals such as LVDS. Like this, we can avoid that the signal line acts as an antenna and emits high-frequency radiation.
• Once a prototype has been assembled, we perform pre-testing in an EMC lab.
• If the result from the pre-test in the EMC lab is negative (i.e. emissions exceed the limit), we try to identify the causes of the emissions and fix them in the design lab, then check the fix again in the EMC lab.

Pre Compliance Testing

Here in Switzerland, one iteration costs the equivalent of approximately USD 1'000 to 2'000 for a half-day testing session of a simple device. The operator will install the device in an anechoic chamber and run a test procedure.

Pre-test of the astronomical camera (at the right side) in an anechoic chamber

The result is a graph which displays the radiation at each frequency. The red line shows the limit, the green line is the actual power of the emission.

First result of our pre-testing

In our case, a hand full of peaks numbered 1 to 7 in the picture above exceeded the limit between 200 MHz and 700 MHz.

The EMC lab provided a desk with soldering iron, wires, resistors and so on so that we could try small design modifications and quickly repeat the test. For example, we tried to add a small resistor in a clock line (which had little effect on the emissions).

Fixing

With the result from the pre-testing, we need to return to the design lab and try to figure out what’s causing the unwanted radiation. A very helpful tool in this case is a spectrum analyzer and an EMC probe. Even though we won’t get accurate results as in the EMC lab, the spectrum analyzer can help us to see the effect of changes that we make to improve the emissions.

For the astronomical video camera, we recognize the various peeks already seen in the pre-testing between 200 and 700 MHz.

Reproducing the emissions in the lab

A detailed analysis revealed that the emissions are caused by a single-ended 74 MHz clock line from the FPGA to the image sensor. Every single peak that violates the limit is a multiple of these 74 MHz, e.g. 4*74 MHz = 296 Mhz.

Reducing the drive strength of the clock signal and slowing down the edges results in a slight improvement:

Reduced drive strength and edge speed

The peaks are down by a few dB, but certainly not enough. Another idea is to use spread-spectrum clocking. This helped a lot:

Significant improvement with spread-spectrum clocking

As we needed to fix some minor issues in the design anyway, we decided to apply a small hardware fix as well. We’ve included a small LC filter in the signal line, close to the FPGA case.

Next steps

Right now, we’re waiting for the modified boards to arrive. Once they’re here, we’ll check if the desired improvement is visible, and if this is the case, we’ll ask the EMV laboratory to create a full test report for conformity with the RAD specification. Afterwards, what will remain to be done are steps 5 (technical documentation) and 6 (CE marking, declaration of conformity).

We plan to document our experience in an upcoming part 2 soon…

I hope you enjoyed reading. Feel free to contact us at info@classycode.com if you have any questions or comments.