Ondo - Thermometer for iOS

Measure indoor room temperature using your iPhone or iPad and headset (required).

Ondo is an experimental acoustic thermometer implemented using an iPhone (or iPad) and headset. Acoustic thermometers utilise the principle that the speed of sound in air changes with temperature; by measuring the speed of sound it is possible to calculate air temperature.

How it works?

Ondo transmits a high frequency sound from the headset earpiece. This sound is received by the microphone positioned a short, fixed distance from the earpiece. The time taken for the sound to travel between the earpiece and the microphone is very accurately measured to less than a millionth of a second.

What you will need to build your acoustic thermometer:

Standard Apple headset (EarPods with lightning connector)

Old credit or debit card (to provide a base)

Four elastic bands (to hold the right earpiece and microphone in position)

iPhone or iPad with Ondo installed

Getting started:

Follow the simple instructions in the app (or on the website www.ondo.app) to build your headset thermometer

Calibrate to the starting temperature and your thermometer is ready to use

Move the phone and headset to a different temperature zone e.g. take it outside or move nearer to a heater and watch the reading change

Specification:

Temperature range -40 to 50 degrees Celsius

Accuracy +/- 1 degree (dependent upon headset fixing)

PLEASE NOTE - This app will only work with a headset connected and set up according to the instructions in the app. Please do not buy this app if you do not have a suitable headset. This app will not work with AirPods.