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The map of the territory, and the principles everything else is built on.
Objects, tools and activities: how Sentio is put together
Three concepts explain the whole app: tools measure, objects remember, activities chain several tools into one job. Worked examples, and why the tool list keeps growing.
OverviewWhat can a phone actually measure?
A modern phone carries a microphone, cameras, a torch, a vibration motor and an accelerometer. Combined deliberately, that's a small laboratory — the map, from single-sensor tools to two-phone setups.
How it worksWhy a measurement app should work with the network off
Analysis runs on the device, results arrive in under a second, and nothing leaves the phone unless you sign in and press sync. Why offline-first is the load-bearing constraint.
OverviewPhone vs. professional instruments: an honest accounting
Frequency and time are nearly free; absolute amplitude is expensive. Where a phone genuinely competes, where it's a screening tool, and where the calibrated instrument is simply the right answer.
Listening: sound and motion
The microphone and accelerometer — passive listening, and the phone exciting the world itself.
The tap test: what a knock tells you about ripeness
Resonance and damping shift as fruit ripens, and a phone microphone can hear both. How the knock test works, and why every scan doubles as training data.
Use caseWhat is this made of? Tap it and listen
Solid wood or veneer, real stone or laminate — materials ring differently. The tap test for materials, and the guided activity that demands agreement between taps before naming a family.
Use caseThe frequency fingerprint: what a spectrum tells you
Hums, motors, fans and rattles all have a spectral signature. Record a sustained sound, see where the energy sits, and compare the same machine against its healthy self.
Use caseVibration signatures: set the phone down and let it feel
Washing machines, compressors, 3D printers — the accelerometer reads low-frequency, structure-borne vibration the microphone misses, and repeated measurements reveal drift.
Use caseHaptic response: the phone that shakes itself to listen
The vibration motor excites while the accelerometer and microphone record how the object answers — an active probe that tells hollow from solid.
How it worksBand levels: measuring sound the way acousticians do — almost
Real acoustics happens in frequency bands, not single decibel numbers. The self-identifying sixteen-tone sweep, per-band signal-to-noise gates, and an honest map of the gap to an IEC 61672 class 1 meter.
Looking: the camera as instrument
Color, light, flicker, counting, sizing and reading — and the torch as a light source you control.
Color and light: the camera as colorimeter and light meter
Spot color for paint and produce, ambient brightness for desks and plants — and why comparisons of the same setup are the claim you can trust.
Use caseBlinking lights and spinning things
Time an LED's flicker, decode an indicator's blink pattern, estimate a fan's rotation rate — and the stroboscopic experiment that goes beyond the frame rate.
Use caseTorch on, torch off: reflectance and translucency
A frame pair with the torch off and on isolates how a surface reflects a known light; pressed against the lens, the same optics candle eggs, leaves and film.
Use caseReading a pulse with a torch and a camera
A fingertip over the lens turns the camera into a photodetector watching blood volume change — and the same physics reads anything that pulses against the lens. A rate, never a diagnosis.
Use caseCount, measure, read: the camera's clerical work
Counting objects in view, sizing things against a payment card, reading a utility meter's digits — small jobs the camera does so numbers land in a catalog instead of a mental note.
Use caseA light meter in your pocket — and why it refuses to say "lux"
A lux meter weighs light the way a standard human eye does; a camera doesn't. What the phone light meter honestly measures, and where a certified illuminance meter is the only right answer.
Use caseMeasuring size with a camera: a credit card and some Renaissance geometry
A photo records angles, not sizes — unless it contains an object of known size. The similar-triangles trick behind the Dimension tool, and when calipers, tapes and laser meters win.
How it worksLight that carries a message: from TV remotes to two phones
Blink a light at a known rate and a receiver can pick it out of any ambient glare — the trick behind IR remotes and Li-Fi, and the working principle of the modulated-light tool.
ResearchFreezing motion with a torch: the strobe experiment
Stroboscopes freeze rotation by flashing at its rate. The research-only Strobe tool tries it with the phone's torch — and is honest about harmonics, latency and why it stays experimental.
Activities: guided procedures for real jobs
When the job needs several measurements in the right order — and an app that refuses to guess.
Tuning bike spokes by ear, with instructions you can act on
Pluck a spoke and it rings at a pitch set by its tension. A guided activity turns that into per-spoke instructions — which way to turn the wrench, seen from where you stand.
Use caseTwo phones, one wall: measuring sound insulation
One phone emits a known sweep, the other listens on both sides. The same-receiver ratio cancels both devices' calibration — no sync, no cable, no lab.
Use caseGlass transparency and the quarter-turn polarization test
One phone blinks its screen, the other watches through the pane — the ratio is the transparency. Turn the emitter 90° and the same rig answers whether the sample polarizes.
How it worksA hearing screening the phone can defend
Six frequencies, an adaptive ladder, a room check, and a loopback through the phone's own microphone — how a speaker-and-earbud-free hearing screen earns its error bars. Not an audiogram, and it says so.
How it worksA vision test where the phone measures the distance too
Acuity is an angle, so letter size means nothing without distance — the screen is the chart and the front camera is the tape measure, tracking you continuously.
Use caseWhat material is this? Anatomy of a guided activity
Three agreeing taps, a vibration probe with veto power, and a reference object that outranks the classifier — how the material-identification activity chains tools into one defensible verdict.