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Where Should I Connect My Ground Probe

Liam Cadigan

Most electrical engineers do not get much formal lab training on the use of signal measurement tools outside of an academic setting, instead it is left for them to learn in industry. This works well enough for most engineers, some will never return to the lab after they leave school, others spend every single day in their lab but use equipment which is so specialized that their school never would have had it anyways.

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In general, you’re quite lucky if you come out of school with detailed knowledge of test and measurement equipment. For lab-borne EE's, knowing how to properly tune scope probes, diagnose RF issues, and deal with ESD sensitive components is critical for them to contribute effectively. Equally important is knowledge about signal integrity during measurement.

At high frequencies the ground clip on an oscilloscope probe will become highly inductive and distort any measurement being taken - for that reason a spring clip probe connected to the nearest ground point is often used. The shorter ground clips are easy to come by, everyone has them - however finding the closest ground point to your signal is often difficult to do and will change for any board design.

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That’s why we have built this kind of powerful functionality into inspectAR directly. With our ‘Edit Overlay’ dialog, you can filter out CAD data which isn’t necessary for the type of electronics lab work you are doing. For example, if you need to find the closest ground point to a pin in order to make a high frequency measurement simply select the ground net to display it. From here you can adjust the transparency of the net in case you need to see underneath it in order to probe. Then filter out any layers you don’t want to see by clicking on them, I suggest displaying only one layer when taking measurements, such as the top layer. After that filter out anything that you are unable to probe like traces, fills, and in most cases vias.

'Edit Overlay' Menu

Boom! There you go, now all you see is the net you selected (highlighted, click on it again in the active overlays pane if it is not) and the net you are referencing against.

GND net filtered to show only 'probable' points (pads)


How will we make it even better? A new feature is in the pipeline to give every net a different colour so that it is even easier to distinguish between one net and another.

Need more information? One of the best books on electronics lab work is available for free online. Right the First Time Demystifies many aspects of PCB design and is available for free online.

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