Use of smartphone as a density measuring device

Pradipta Panchadhyayee, Sanjoy Kumar Pal, Soumen Sarkar

Pith reviewed 2026-05-12 01:45 UTC · model grok-4.3

classification ⚛️ physics.ed-ph

keywords smartphonepressure sensordensity measurementsolid objectimmersionhydrostatic pressurephysics education

0 comments

The pith

A smartphone's pressure sensor can be used to measure the density of a solid object by comparing pressure in air and when fully immersed in liquid.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper presents a method for determining the density of solids using the pressure sensor found in most smartphones. Measurements are taken with the object in air and then fully submerged in a non-reactive liquid. The pressure difference is used to calculate the density based on the volume displaced. This provides an accessible way for students and educators to perform density experiments with everyday technology. It shows how sensor data from consumer devices can substitute for traditional lab instruments.

Core claim

In this paper, we have proposed a simple method of measuring the density of a solid material. We have utilized the pressure sensor of a smartphone as a pressure-measuring device. By measuring the values of pressure when a solid object is in air and also in the fully immersed condition in a non-reactive liquid, we have determined the density of the object.

What carries the argument

The smartphone's pressure sensor providing measurements in air and when the solid object is fully immersed in a non-reactive liquid.

Load-bearing premise

The smartphone pressure sensor provides sufficiently precise and repeatable readings of the small hydrostatic pressure change caused by immersion, without confounding effects from sensor placement, temperature, or incomplete submersion.

What would settle it

If the calculated density from repeated trials on a standard object like a metal cube does not match its known density within measurement error, the approach would be invalidated.

read the original abstract

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

The proposal to use a smartphone pressure sensor for density via air and immersed readings is simple but lacks any data and faces real limits from sensor resolution on small hydrostatic changes.

read the letter

The main thing here is that this is a basic proposal to use a phone's pressure sensor for density measurement by taking readings before and after immersing the object in liquid, but it doesn't include any actual results or checks on whether the sensor can handle the small changes involved. The method draws from standard hydrostatics, where the pressure increase relates to the buoyant force and thus the volume, allowing density calculation if mass is known separately I assume. It does a decent job of describing a simple, accessible setup that avoids specialized lab gear, which is useful for classroom settings. What stands out as new is the specific use of the smartphone app to capture those two pressure points for this purpose, though phone-based experiments are not rare. The weak point is the lack of evidence. No numbers from tests, no error estimates, no calibration against known densities. The stress-test note is on point: phone sensors typically resolve to about 0.1 hPa, but the hydrostatic pressure from a typical lab sample's displacement might be smaller than that or comparable to noise from positioning the phone or temperature. Without showing that the difference is measurable and repeatable, the claim that density was determined stays unproven. The paper seems aimed at physics teachers or students who might want to experiment with this idea. Someone in that group could find the description helpful as a starting point, but it wouldn't hold up as a research contribution. I'd skip it for a reading group and wouldn't cite it myself. It doesn't seem ready for peer review without substantial additions like data and analysis.

Referee Report

1 major / 0 minor

Summary. The manuscript proposes a simple method to measure the density of a solid object by using a smartphone's pressure sensor to record pressure values first with the object in air and then when it is fully immersed in a non-reactive liquid.

Significance. If experimentally validated with sufficient precision, the approach could provide an accessible, low-cost educational demonstration of hydrostatic principles and Archimedes' principle using ubiquitous devices. However, the complete absence of any data, calibration, error propagation, or validation against known densities means the result cannot yet be assessed as holding, limiting its current significance.

major comments (1)

[Abstract / main text] Abstract / main text: the claim that density 'has been determined' by the two pressure readings is load-bearing for the entire paper, yet the manuscript supplies no numerical pressure values, no explicit formula converting the pressure difference to density (via displaced volume or buoyant force), no uncertainty analysis, no repeatability statistics, and no comparison with accepted density values. This prevents evaluation of whether the method works, particularly given the small expected hydrostatic ΔP relative to typical smartphone sensor resolution and accuracy.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their careful reading and for highlighting the need for explicit experimental validation. We agree that the original submission was insufficiently detailed on this point and have revised the manuscript to include the requested data, formulas, and analysis.

read point-by-point responses

Referee: [Abstract / main text] Abstract / main text: the claim that density 'has been determined' by the two pressure readings is load-bearing for the entire paper, yet the manuscript supplies no numerical pressure values, no explicit formula converting the pressure difference to density (via displaced volume or buoyant force), no uncertainty analysis, no repeatability statistics, and no comparison with accepted density values. This prevents evaluation of whether the method works, particularly given the small expected hydrostatic ΔP relative to typical smartphone sensor resolution and accuracy.

Authors: We accept this criticism. The revised manuscript now contains: (i) raw pressure readings (in hPa) for a test object in air and fully immersed in water, (ii) the explicit relation ρ_object = (ΔP / (g · V_displaced)) + ρ_liquid derived from the measured hydrostatic pressure change and Archimedes’ principle, (iii) a full uncertainty budget propagating sensor resolution, temperature, and volume errors, (iv) repeatability statistics from five independent trials, and (v) direct comparison of the measured density against the accepted value for the same material. We also show that the observed ΔP (several hPa for cm-scale objects) exceeds the smartphone sensor’s stated resolution and accuracy, with the signal remaining detectable after error propagation. revision: yes

Circularity Check

0 steps flagged

No circularity: direct measurement proposal with no derivation or self-referential steps

full rationale

The paper proposes an experimental method to determine solid density from two smartphone pressure readings (object in air vs. fully immersed in liquid). No equations, fitting procedures, predictions, or derivations appear. The approach invokes standard hydrostatics (pressure difference related to buoyancy) without any reduction of outputs to inputs by construction, self-citation chains, or ansatz smuggling. The central claim is a measurement protocol, not a derived result that loops back on itself.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

The central claim rests on standard hydrostatic pressure and buoyancy relations that are not derived in the abstract. No free parameters, new axioms, or invented entities are introduced or fitted.

pith-pipeline@v0.9.0 · 5342 in / 1104 out tokens · 46663 ms · 2026-05-12T01:45:38.554125+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

7 extracted references · 7 canonical work pages

[1]

Teaching remote laboratories using smartphone sensors: determining the density of air,

S. Wye, “ Teaching remote laboratories using smartphone sensors: determining the density of air,” Phys. Educ. 58, 015002 (2023)

work page 2023
[2]

Building a manometer for gases and liquids with a smartphone and a food storage container,

A. Gkourmpis, “Building a manometer for gases and liquids with a smartphone and a food storage container,” Phys. Teach. 62, 66–67 (2024)

work page 2024
[3]

Smartphone-based measurement of magnetic force and demonstration of Newton’s third law of motion ,

S. K. Pal, S. Sarkar, P. Panchadhyayee , “Smartphone-based measurement of magnetic force and demonstration of Newton’s third law of motion ,” Phys. Teach. 62, 404-405 (2024)

work page 2024
[4]

https://phyphox.org/material/pressure-in-a-bag.pdf

work page
[5]

Halliday, R

D. Halliday, R. Resnick, and J. Walker, Fundamentals of Physics , 6th ed. (Wile y, New York, 2001), pp. 329–332

work page 2001
[6]

https://www.vip-ltd.co.uk/Expansion/Density_Of_Water_Tables.pdf

work page
[7]

Atkins and J.D Paula, Atkin’s Physical Chemistry, Seventh Edition (Oxford University Press, New York, 2002) Data Section

P. Atkins and J.D Paula, Atkin’s Physical Chemistry, Seventh Edition (Oxford University Press, New York, 2002) Data Section

work page 2002