# J-Thermo

> iPhone thermometer app using audio jack probe for real-time temperature measurement. (iPhone/iPad app by Kwan Shing Marco Li.)

- Source: https://appshunter.io/ios/app/j-thermo/id987891588 (this page in markdown: same URL + `.md`)
- Developer: [Kwan Shing Marco Li](https://appshunter.io/developer/987891587)
- Category: Utilities, Food & Drink
- Price: Free
- Rating: 5.00/5 from 1 App Store ratings
- Age rating: 4+
- Requires: iOS 8.0 · 1 MB
- Languages: English
- Released: 2015-06-11
- Data updated: 2026-06-25
- Monetization: free
- User reviews in markdown: https://appshunter.io/ios/app/j-thermo/id987891588/reviews.md

## What is J?

J-Thermo is an thermometer that plugs into audio jack of your iPhone/iPad. 

Features:
-Plug and Play! No setup required
-Measurement range from -50 to 150 °C (-58 to 302 °F)
-125 mm stainless steel sensor probe
-Real-time temperature measurement in both °C and °F
-Highest, lowest temperature display
-No battery required.
-Temperature higher than 150 °C or 302 °F is treated as HH.H.
-Temperature lower than -50 °C or -58 °F is treated as LL.L.


How to use:
1.  Open "J-Thermo" app.

2. Firmly plug the J-Thermo into the audio jack of iPhone/iPad and turn the headphone volume to maximum.The temperature reading shall be shown in a few seconds. 

3. When you finished using J-Thermo, press "Done", then plug out J-Thermo from iPhone/iPad.

(Please make sure the app is opened when the iPhone/iPad is in portrait mode, otherwise the UI will be abnormal. An update will be released soon to fix this.)


Troubleshooting:
If the J-Thermo is not showing the temperature reading, please check the following:
-If the app shows "No J-Thermo detected" or "No data from J-Thermo", please manually turn the headphone volume to maximum.
-If the app shows "Cannot access microphone due to privacy setting", then please turn ON the microphone accessibility in privacy setting for "J-Thermo" app.
-Please make sure "Volume Limit" is turned off in "Settings" of iPhone/iPad.
-For iPhone/iPad purchased in EU, the EU volume limit may apply to devices which means the headphone volume maybe lower, therefore it is not guaranteed that J-Thermo will work. If there is "EU Volume Limit" in "Settings", please turn it off and try.

Contact us:
If you have any enquiries, please contact
marco@carrin.com.hk

## Key features

- Plug and Play setup
- Real-time temperature measurement
- Celsius and Fahrenheit display
- Wide measurement range (-50 to 150 °C)
- No battery required
- Stainless steel sensor probe


## Frequently asked questions about J

### How do I use J-Thermo?

Open the J-Thermo app, plug the J-Thermo probe firmly into your iPhone/iPad's audio jack, and turn the headphone volume to maximum. The temperature reading should appear within seconds. Ensure the app is open in portrait mode for correct UI display.

### What is the measurement range of J-Thermo?

J-Thermo can measure temperatures from -50 to 150 °C (-58 to 302 °F). Temperatures outside this range are displayed as HH.H (above 150 °C) or LL.L (below -50 °C).

### Does J-Thermo require a battery?

No, J-Thermo does not require a battery. It draws power from your iPhone or iPad through the audio jack connection.

### What should I do if J-Thermo is not showing a temperature reading?

Ensure your headphone volume is at maximum. If the app shows 'No J-Thermo detected,' try manually setting the volume. Also, check your iPhone/iPad's privacy settings to ensure microphone access is enabled for J-Thermo.

### Is J-Thermo compatible with all iPhones and iPads?

J-Thermo is designed for iPhone, iPad, and iPod devices. However, for devices purchased in the EU, an 'EU Volume Limit' in settings might affect its functionality, so it's recommended to turn this off if present.

### What is the update frequency for J-Thermo?

The latest version, 1.1.0, was released on June 11, 2015. An update to fix UI issues in landscape mode was planned for release soon after the initial launch.

### What is the age rating for J-Thermo?

J-Thermo has an age rating of 4+, making it suitable for a wide range of users.

### What are the highest and lowest temperatures J-Thermo can display?

J-Thermo displays the highest and lowest temperatures recorded during a session. It also has specific indicators for temperatures exceeding its measurement range: HH.H for above 150 °C and LL.L for below -50 °C.

## Version history (last 1 release)

### 1.1.0 — 2015-06-11

This app has been updated by Apple to display the Apple Watch app icon.

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## More apps by Kwan Shing Marco Li

- [J-UV](https://appshunter.io/ios/app/j-uv/id1073037537)
- [J-TH](https://appshunter.io/ios/app/j-th/id1148916918)
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All apps by Kwan Shing Marco Li: https://appshunter.io/developer/987891587

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-06-25.*