Project update 9 of 10
"There have been times when I didn’t quite make my deadline." -Akira Toriyama
Ship-day is approaching and we are not ready. It’s a drag, but it’s not for lack of trying. The major holdup has not been manufacturing, thankfully, but compliance.
To ensure that our European customers get their BeanCounters without incident, we’re required to CE mark. BeanCounter, being a relatively simple battery-powered device, is only required to comply with a few basic directives. The first is RoHS, or the "Directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment" if you’re not into that whole brevity thing. RoHS restricts the use of a handful of hazardous chemicals in the production of electronic equipment, nasty stuff that you don’t want floating around like Cadmium, Mercury, and Hexavalent Chromium. This one is easy, I just need to compile the RoHS-compliance paperwork from my component suppliers and the PCB manufacturer. Unlike the next thing we’re going to talk about, if every piece is compliant, then the whole is compliant.
The second is EMC (Electromagnetic Compatibility) which is basically an edict to "play nice" with everything else in the electromagnetic spectrum by limiting the RF noise that they radiate. This is difficult and frustrating to characterize, but it is important. The fact that you and all of your neighbors likely have mobile phones, microwave ovens, WiFi access points, PCs, and a pile of switching power supplies in your homes and they all work at the same time is—frankly—shocking and it’s only possible because (almost) everyone follows the rules about emissions and immunity. As a manufacturer, the only way to know for certain that your device is "playing nice" is to measure the emissions in a quiet environment using calibrated instruments. This is, in theory, something that you can do on your own. In fact, with regard to the CE mark in particular, most products can be marketed with a simple Declaration of Conformity from the manufacturer. No third-party is required to verify compliance, it’s sufficient that the manufacturer accepts liability. It is required, however, that you collect and keep all of the design files, test-results and paperwork by which you’re claiming conformity in what’s known as a "technical file." So why is it that most manufacturers don’t test for compliance in-house? In short: it’s hard.
Making EMC measurements in a world that’s full of EMFs is difficult. In order to ensure accuracy, these measurements need to be made in a well shielded and characterized environment. Shielded anechoic chambers, transverse electromagnetic cells (TEMs) and GTEMs (Gigahertz TEMs) are often utilized to block outside noise and internal reflections, while allowing for quanititative measurement of the EM field surrounding a device under test. The measurements themselves have to be made using sensitive and accurate instruments such as spectrum analyzers which, themselves, must be periodically calibrated. All of this represents a hefty capital expenditure, not to mention the person-hours involved in actually doing the work. That said, owning equipment and knowing how to operate it is only a small fraction of the whole picture.
You can take all of the measurements you want but without anything to compare them to, you’re not actually proving compliance. So how do you know what a "passing grade" is? How do you even know what counts as a valid test? You read the standards which are referenced in the directives. Easy, right? Yes and No. Depending on your application, it can be an engineer’s entire job to know which directives apply to a given device. Even if you’re able to identify the directives with some confidence, obtaining the letter of the standard is not as easy as a quick google search. It may be surprising to hear that the standards are expensive. A PDF of a single standard can cost hundreds of dollars and most devices are required to comply with several directives which each reference several standards. Between the cost of the standards, the fact that they are sometimes amended or retired, and the labor involved in knowing which ones apply, it’s no wonder why most manufacturers outsource conformity assessment to dedicated testing labs even when they’re not legally required to do so.
Originally, my plan was to approach this the same way that I approach many business challenges which is to simply do it myself. I got as far as collecting equipment: I currently own a digital spectrum analyzer with a tracking generator, a used Tescom TC-5064C test cell, the appropriate SWR bridge to characterize the VSWR in the chamber, etc. However, it’s quickly becoming apparent that self-testing is a nearly limitless money-pit and without any guarantee that the results will be accurate and sufficient, it’s becoming harder to justify. In response, I’ve decided to hire a professional testing lab. This will ensure that BeanCounter conforms with the relevant directives and allow me to concentrate on QA and fulfillment. The downside to hiring a lab this late in the game is that it pushes the delivery timeline by several weeks. While I’ve been able to make preparations for final assembly, I’ve made the decision to hold off on the assembly itself until BeanCounter gets a passing EMC test result in case any mitigation is required, which would be easier to implement during assembly.
Well… I have them now, so I might as well learn to use them. My plan currently is to use the professional test results as a touchstone for my own measurements later on. If I can make equivalent measurements and replicate the test results, then I’ll have some confidence in my understanding of the equipment and standards. At that point, I would feel comfortable investing more money in the toolchain and it may very well be that our next product is completely tested in-house.
All of this is to say that BeanCounter delivery will be delayed by several weeks, with our new expected fulfillment date being End of May. I know this is not uncommon among crowdfunded hardware projects, but I still don’t take it lightly. Thank you for your patience and continued support as I work to deliver a product that I can feel confident in and which ticks all of the boxes. Expect a forthcoming update about test results and assembly jigs.