The Importance of Measurements

How much do we trust our gut when doing our job? Sometimes we can allow our experience to guide us without referring to the calculator. Physical units, such as those used to define mass and distance, are easy to visualize. They form such a familiar part of everyday life that many of us are able to estimate a length or weight with some accuracy.

But what about an Amp? Could we make a guess about the current flowing through a lamp? Without knowing the resistance of the wire or the voltage rating of the power source, we couldn’t begin to make an accurate estimate – the variables simply make it unreasonable, and no engineer should guess without this additional information. Even so, an Amp is a finite measurement, but sometimes we use language that cannot be so clearly quantified.

I get to talk to a lot of connector manufacturers. I enjoy keeping up to date with the latest developments in connectors, and so I attend webinars and online training events as often as I can.

My most recent meeting was a briefing on a new range of precision RF (radio frequency) connectors. RF is an aspect of connectors with which I am less familiar, and so I welcomed the chance to learn more. The state of the art in RF connectors is enough to make my little brain hurt. The scale of the performance is amazing. The connectors in question were designed to test the latest semiconductors and were capable of frequencies in excess of 70 Gigahertz.

When I started in the industry, connectors that were capable of more than 1 Gigahertz were considered extremely high speed. Now, frequencies of less than 12 Gigahertz are described as low, and manufacturers are actively working on products that work in excess of 100 Gigahertz.

Terms like high-speed are therefore too vague, and yet we use them quite often. There are plenty of other phrases that are also common in the electronics world like high-voltage and high-power. But what do they actually mean?

The answer to all of these questions is, “it depends.” High power means different things to different people. To a connector manufacturer specialising in small board-to-board connectors, high power might represent a current of 5 Amps. A different manufacturer who is active in the electric vehicle market will regularly have to contend with currents that are more than one hundred times greater.

The definitions of these phrases are therefore entirely in the eye of the beholder. And yet they are phrases that we continue to use. The phrase with which I want to take issue today is “finger-tight,” because it has a real-world impact in the world of electronics.

A Newton is a measure of force and is quite easy to guess. Rather fittingly, a small apple at rest exerts a downwards force of about 1 Newton. However, Newtons are also used to measure the rotational force (torque) as part of a unit called Newton-meters, and this is more difficult to estimate. How much torque is required to undo the lid of a pickle jar? I’ll save you the google search – the answer, as before, is that it depends. However, a rough guess would be anything between 3 and 6 Nm.

The reason I use this as an example is that torque is important when it comes to components. To assemble circular connectors or panel-mounting switches correctly requires the engineer to apply the correct torque. There is a temptation to assume that it does not matter. Some might assume that “finger tight” is enough, while others will keep leaning on a spanner until it doesn’t move anymore. The problem is that too much torque, or too little, can hide a problem that might not be apparent on visual inspection. Regardless of how expensive and well-made the components are, cables can be crushed, O-rings can be deformed, and seals can be compromised.

A few years ago, I explored the testing required to certify a switch as vandal-proof. I won’t bore you with the whole story – you can read it here if you are interested – but the summary is that I broke two switches because I didn’t follow the instructions and apply the right torque.

Torque spanners are not hard to use. However, I decided not to use the correct tool and assumed that finger-tight (or my other favourite method which can be described as “tighten it until it squeaks”) was good enough. The truth is that, even if you have spent a lot of money on a high-performance component, you are putting your design at risk if you do not read the instructions and apply the correct force.

And so, I would like to leave you with three suggestions. I wouldn’t call them golden rules, but they could certainly make you a little richer. Or, at least, less poor…

The first lesson is that it pays to be specific. Terms like high-power or high-speed are of limited value in anything but the vaguest conversation. When talking to suppliers, colleagues or customers, it is always worth making sure you that are clear in your communication.

The second lesson is that it is risky to trust your gut. As we have seen with torque measurements, even experienced engineers can come unstuck if they adopt a strategy of “that’s good enough.” If a design is important enough to install an expensive component, it is important enough to buy the right tool for the job.

Finally, read the manual, and make sure to follow the instructions faithfully. It may take a little longer and cost a little money, but it will be worth it in the end.

Because saving the price of the correct tool will cost you more in the long term.