Safety Critical Electronics Design & High Complexity Electronics Manufacture

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What is SIL?

Safety Integrity Level

The term SIL is referred to a lot within the functional safety world, but it is often miss-understood. It is the safety integrity level of an overall safety function. Since Mutech design equipment that form part of a safety function, the task is to produce equipment that is capable of meeting the overall safety function. Since there are two types of failure, that essentially requires meeting two criteria:


………. 1. Systematic capability (SC). This is employing suitable techniques and measures suitable for the target SIL, and this is classified such that (for example) SC2 is normally suitable for SIL2.


………. 2. Hardware failure rates. The SIL will define a required failure rate for the overall safety function, and generally a percentage of that is allocated to the element. Quite often when designing elements, the rest of the safety system is not known and hence a reasonable proportion is assigned.


MK Test Systems

Complete Electronics and Software Design of the ExLRT Loop Resistance Tester

A result of a long-term project between The Boeing Company and MK Test Systems, the ExLRT is an intrinsically safe loop resistance tester.

Loop resistance testers are commonly used by aerospace MROs (Maintenance, Repair & Overhaul) to test earth bond resistances. The existing tools available on the market aren’t intrinsically safe so can possibly generate sparks. In an MRO environment, the aircraft’s fuel tanks are potentially explosive chambers just waiting to be set off. While this might be fun to watch in the movies, in real life this could be catastrophic. This is why Intrinsic Safety is paramount, but was lacking.

Boeing challenged MK Test Systems to create an Intrinsically Safe version of their existing BLRT loop resistance tester. The finished product went further than that by meeting or surpassing all the performance requirements of the existing unit. It is a tool that is also easier to use and offers more powerful features. The device must perform measurements accurately and correctly; the performance requirements are as demanding as the intrinsic safety requirements.

The need to balance these two often contradictory needs presented many interesting challenges during the design of the ExLRT, such as creating customised couplers, using very low currents and high inductances to prevent sparking, but still provide a sub-milliohm level of accuracy. Mutech’s expert understanding of Intrinsic Safety systems enabled MK Test Systems to develop a tool which achieved all the criteria required by Boeing.

This was a complex project and has resulted in a specialised tool suitable for today’s testing environments and quality standards. MK Test Systems and Mutech worked together to develop this next-generation loop resistance testing tool by collaboratively addressing these problems.

IEC Young Professionals’ Program

Mutech design engineer Tim Cameron is chosen by BSI for the IEC Young Professionals’ Program 2019

What is the IEC Young Professionals Program?

“The IEC is an international organisation responsible for industrial and technical standards. They run the Young Professionals Program (YPP) each year, to encourage younger talent to get involved in writing the standards of tomorrow. There are about 150 young professionals on this program from across the world, 3 of whom are from the UK. We will be witnessing first-hand the next IEC meetings in China.”

How did you find out about it and why did you apply for the program?

“Our company director, Colin, has been introduced to some of the young professionals through the IEC committees he is involved with and so has been aware of the program for some time.”
“As a company we want to broaden our understanding of general standards writing and conformity assessment, as we currently have a knowledge of specific standards, relating to explosive atmospheres.”

Tim Cameron Profile

What do you expect to achieve?

“Well, that’s the tricky part, because I don’t have specific goals for this. I’m primarily seeing it as an information gathering opportunity, to gain exposure to the standards industry and to further Mutech’s visibility to that world, I will definitely purchase myself an orange tie! But mostly my plan is to go out there, to see what’s going on, to see the program the IEC puts on and the opportunities that come out of it. I’m keen to understand what’s worth getting involved in, because there might be standards that align well with our practices or new areas of industry that are advantageous to us.”

You were at BSI for a preparation day recently, how was it?

“The visit the other week to Richmond was a chance for me and the two other candidates, Samantha and Rob, to get to know each other. It was an opportunity to be introduced to the British Standards Institute (BSI) and to find out about what they do and are involved with. It was also a chance for them to explain to us more about the YPP and what we should expect from the other meetings we will have, including the visit to Shanghai. The overall impression I got was that we are going to be very busy in China!”

What’s next?

“Before we head out to Shanghai, we have some interviews booked with BSI about the YPP to help raise the profile of the program. We will then head out to Shanghai for the main event, I will be out there for 6 days. Whilst there, we’ll get a choice of which lectures and activities we would like to be involved in, from lectures on artificial intelligence to power station visits, as well as the opportunity to observe committee meetings and take part in workshops and possibly have input into some standards writing.”

“I’m hoping to have time for fun too. Ganbei!”

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