The Align asks you for one number before you start: how far the handpiece may drift before it says something. This note is about what that number does, why the range is what it is, and how to think about picking one.
What the limit is measured against
It is worth being precise, because this is the part people get wrong. The limit is not an angle in the room. It is a distance from a reference you set.
When you zero the device, you are telling it "this orientation, right now, is the one I intend to hold". Everything after that is measured from there. A limit of 10° means ten degrees away from wherever you were standing when you pressed the button — not ten degrees from vertical, or from the tooth, or from anything the device could work out on its own.
This has a practical consequence that catches people out: if you zero the device while the handpiece is already in the wrong position, it will faithfully hold you to the wrong position. The device has no opinion about whether your reference was a good one. That is your judgement, and it stays your judgement.
The range, and why it stops where it does
The limit is selectable from 5° to 20°, in 1° steps. Press the button to step up; past 20° it wraps back to 5. The default is 10°.
Both ends of that range are deliberate.
It does not go to zero. A zero-degree limit sounds like maximum precision and is in fact useless: no hand holds an instrument perfectly still, so the device would alert continuously and you would switch it off within a minute. Any tolerance below a few degrees is smaller than the natural tremor of a steady hand.
It stops at 20°. Past roughly that point the alert stops being feedback and becomes an announcement of something you had already noticed. A drift large enough to need a 25° or 30° threshold is a drift you can see.
The 1° steps are there because the useful part of the range is narrow. Between 5° and 20° there are sixteen settings, which is enough resolution to find the one that suits a particular exercise without making the selection itself a chore on a single button.
How to think about the choice
The trade is the same one every alerting system faces, and it is worth naming plainly.
A tight limit catches drift early, which is what you want when the point of the exercise is holding still. It also alerts more often, and an alert that fires constantly stops being information. People stop hearing it, then they turn it off.
A loose limit stays quiet through normal movement and speaks only when something has genuinely changed. It also lets a slow drift accumulate for longer before you hear about it.
Neither setting is more correct. They are answers to different questions: am I holding still? versus have I ended up somewhere different?
A pattern that works
Starting loose and tightening is more successful than starting tight, in our experience watching people use it. Beginning at 15° or 20° gives you a period where the device is mostly silent and you learn what it feels like when it does speak. Tightening a few degrees at a time from there gives you a sense of where your own steadiness actually sits.
Starting at 5° tends to produce a device that alerts constantly on the first attempt, which teaches the wrong lesson: that the tool is noise.
The default of 10° exists because it is a reasonable middle for someone who has not yet formed a preference — not because it is optimal for any particular task.
Re-zeroing is part of the workflow, not a failure
The reference is cheap to reset, and it should be reset whenever your intended angle changes. Moving to a different surface means a different target; the reference should move with it. Holding the old reference across a genuine change in intent produces alerts that are technically correct and completely unhelpful.
This is also the honest answer to sensor drift. Any inertial device accumulates a slow error over time. Rather than claiming this does not happen, the device is built so that correcting it costs one button press.
What the limit does not do
- It does not tell you which angle to hold. Choosing the target is a clinical decision and it stays with the operator. The device only reports whether you are still on the target you chose.
- It does not judge the work. A preparation held perfectly within 5° can still be the wrong preparation. Angle adherence and quality of work are different things, and only one of them is visible to an orientation sensor.
- A tighter limit is not a better outcome. It is a more sensitive alert. We have not studied whether any particular setting produces better work, and we do not claim that it does.
The short version
Pick a limit that is quiet enough that you keep the device switched on, and tight enough that when it speaks, you learn something. Start wide, tighten as you get steadier, and re-zero whenever your intention changes. There is no correct number — there is a number that suits what you are practising today.