What you can grab

Pitch is the whole story

A hook clip has a jaw, the jaw has a width, and the width does not change because the component did. Everything about what you can and cannot probe is that width against the spacing of the legs.

The three attachments, and where each ends

Hook clips are the default. Ten of them, colour-coded, sized for 2.54 mm header pins and through-hole leads, and comfortable down to about the 1.27 mm pitch of an SOIC — though on an SOIC two of them on adjacent legs will fight for the space, and one will slip while you are looking at the screen.

Alligator clips are for anything with a tab: a wire end, a battery terminal, a screw-terminal screw, and the ten oversized pads down the edge of the expansion board, which exist precisely so an alligator clip has something to bite. They are too big and too heavy for a header.

The breadboard adapter is for the case where the signal is already on a breadboard, which on this bench is most of them. Push it in at the end of the board, run jumper wires from the rails you care about, and there is nothing to fall off.

When to reach for the soldering iron

At 0.65 mm and below — a TSSOP sensor, a QFP microcontroller — a hook clip is not a marginal grab. It is a short across three pins, and the fact that it sometimes appears to work is worse than it never working.

The answer is a short length of 30 AWG enamelled or Kynar wire, tacked to the pad, brought somewhere with room, and clipped on there. It takes about two minutes per signal.

That is ordinary bench practice and not a compromise. It is also, reliably, faster than the twenty minutes otherwise spent re-seating a clip that keeps letting go — and it gives you a capture you can trust, which is the entire point of the exercise.

What to attach the ground to

Something that is not going anywhere. A ground pin on a header, the negative rail of the breadboard, a mounting hole that goes to ground, a ground test point.

Do not take ground from the pin adjacent to the signal you are probing just because it is convenient. It is the joint most likely to be knocked off, and when it goes you do not get a flat trace — you get the noise capture, which is the most expensive failure in this book.

A note on lead length

The leads in this kit are long enough to be convenient and long enough to be a loop. At the speeds this instrument can resolve that is almost never a problem, so do not go looking for one.

It becomes a problem when the signal has fast edges and the ground return is long: the loop picks up the other channels' switching, and you see ringing that correlates with activity elsewhere on the board rather than with the wire you are on. If that happens, shorten the ground lead and run it beside the signal lead rather than across the bench.