EMC, ESD, RFI, Conformance testing

We have plenty of clients who come to us asking for help with conformance testing.

Sometimes they have submitted a product, had it fail, and now don't know what to do, and sometimes they ask us to go and test as a precursor to formal testing. Of course we regularly get to check our own work doing this - and we're glad to say that there are rarely any big surprises when we do.

Work we regularly undertaken includes:

  • Radiated emmissions testing (does your product interfere with anybody elses radio)
  • Radiated immunity testing (is your product affected by somebody elses radio)
  • Conducted emmissions (will your product spew noise up the mains)
  • Conducted immunity (will noise on the mains affect your product)
  • ESD (ElectroStatic Discharge - will that electric shock you get after walking over a nylon carpet destroy your design)
  • Surge (will a spike on the mains or another cable affect or destroy your design)

We do all the above, to the European Standards required for CE marking, or to other specific requirements you may have

And to a lesser extent (though it's been a hot topic for us for a while):

  • Lightning protection (it's a bit niche, but if your product goes up a pole outside, then you may well need to protect it from surges caused by a nearby lightning hit)

GPS Trackers

We have designed a number of tracking products of late. Some are very simple (and very small), and some have a wealth of clever sensors, support multiple satellite systems, contactless battery charging, can be expanded to add extra features, can record their path and even operate alarms if someone tries to steal them!

The kind of things we had to think very carefully about when designing these were:

  • Very low power usage - how to make a battery smaller than a postage stamp last for months
  • Very low noise design - the signals we are measuring for GPS are tiny (as a GPS expert put it: in the open air, it's like a detecting a fridge lamp from 20,000 miles away - Indoors it's significantly smaller). Normal rules don't apply here, and knowing not just which low-noise parts will do the job, but designing the PCB to stop any noise getting even close to the antenna ports is vital.
  • How to make the product sleep and then wake up for the minimum time possible. Battery life depends on smart usage of "on" time, and by adding an extra 10 cents of hardware and doing a few extra tricks in software it's easy to extend the battery life by several orders of magnitude.
  • Size - one design brief was "as small as possible". The result was smaller than a postage stamp. Another was simply whatever footprint could be acheived with a bucketload of extra sensors and features - try 30x30mm, complete with an on-board 2.4GHz radio antenna.  All these designs need to use PCB design techniques that push the limits of what can be delivered by commercial PCB manufacturers (we're not going to be making millins, so using mobile phone design rules is way too expensive).
  • Expandability - We typically have GSM as a back channel, but what if we wanted to use another system, such as WiFi, Iridium (the sateliite phone system) or a low-power long-range system, like SigFox or LORA?  What if we want to add extra sensors? ..or high quality audio? .. or a camera to stream video?  What if we want to burst data to help avoid detection? All these need careful thought at the architectural stage, as adding them later could mean a total respin - and potentially a bigger product if the original had pushed the PCB design limits!

Digital video

Our engineers spent many years in the digital TV space - designing and manufacuring set-top boxes before then moving across to designing broadcast infrastructure and test equipment for the broadcasters.

Recently we have helped a client realise a PCB for a multi-channel 3G-SDI video switching product. This needed a mindset that is a mix of digital electronics, RF and analogue, with a huge focus on signal integrity, avoiding noise and crosstalk issues and meeting the timing needs of the circuit components. We then helped with the hardware bring-up alongside their own engineers.

RF monitoring system

Our client had an installed base of broadcast equipment that would benefit from having some local monitoring to check that the signals being broadcast are what is expected and still within specification. Thrown into the mix was a wish to also remotely control the broadcast units. We worked with them to define an architecture that mixed an existing computing system, a number of commercial RF measurement units, a bespoke 2U high rack mounted case and a bespoke board providing:

  • RF multiplexing and routing to allow input signals (covering the 1-2000MHz range) to be selected and measured on a round-robin basis, either via on-board AM and FM radio decoders or via off-board measurement systems (e.g. a spectrum analyser)
  • An overcurrent protected power supply for the existing CPU system (and through that, a number of USB devices)
  • A simple serial comms interface to control all the on-board systems (via a small dedicated microprocessor)
  • Phantom power to the RF ports (in case they needed to connect a remote amp or switch to a feed at any point)
  • Audio system to select demodulated audio from the on-board or off-board measurement units, apply manual or digitally controlled amplification, and send it out to headphones.
  • The ability to connect 2 systems back-to-back in the same 2U box.
  • The means to drive a christmas-tree-sized selection of warning lamps and LEDs (including hardware flashing and blinking) 
  • Monitoring of several sensors for temperature, overcurrent, comms failure, etc.
As the hardware was ready well in advance of the software, we also wrote a visual basic test system that allowed us to validate the whole system from a PC or laptop. This same software was then used to test the production units when they were built.

Remote control simulators

Our client makes remote control simulators - systems that emulate the remote that you may use to operate your TV, HiFi, BluRay or satellite system for example.  Their systems are used to test racks of equipment, providing accurate and replicatable IR instructions to a well defined script.

They came to us just after respinning their product, as they had a EMC failure.

We quickly identified the main issue in their PCB layout, but also got chatting about the design in general. To cut the story short, we re-designed the Infra-red outputs of the system to be both more robust, to support a wider range of signals, and support 3rd party transmitters that their customers seemed to want to keep in their installed systems. We also updated the CPUs in the system and added the ability to plug an expansion board in for future options.

.. then we moved on to designing a cut-down version that was just a single channel, mounted in a cost effective plastic box, but which would take the same expansion boards as the previous design

Having now got a small desk-top system that they could plug additonal functionality into, they decided to use it as a development platform for future systems.

The first of these was a RF4CE system - essentially remote control over a 2.4GHz bluetooth style system. We proposed and then designed a system with on-board or switchable off-board antenna (to cater for the big variety of installation modes and the use in a plastic housing), and a CPU-come-radio solution that supported not only RF4CE but also bluetooth or WiFi to provide even further flexibility (for example, allowing WiFi connectivity in their rack product instead of the usual cabled Ethernet connection)

Test systems

This client was very much a small startup when we were recommened to them. They needed someone who could understand their new and quite different technology, and then proivide the means to test it in a controlled manner.  3 years on they have now grown significantly, but we are still providing test solution to them.

Over the years, these have grown from small boards with just a few connectors to wire their tech up to 3rd party measurement kit, to systems with on-board environmental control systems, to very large boards offering self-contained simultaneous multi-channel measurements with huge dynamic ranges that can sit and log test results under many different conditions for days at a time.