# Loggers list

## Detecting Loggers

Open the Efento mobile application. After a few seconds, the app will automatically detect all loggers within the range of your phone or tablet. The list displays each logger’s name, serial number, and current measurement values.

<p align="center"><img src="/files/2iQGDJOINKocFsAS4eWq" alt=""></p>

## Communication encryption

A padlock icon shown next to the logger’s serial number indicates that communication between the logger and the mobile device is encrypted. If a padlock icon appears instead of the measurement value, it means the logger uses encrypted communication and the mobile device is not able to decrypt the data.

<figure><img src="/files/ex2kbxbSzTM9dCnpzv6B" alt=""><figcaption></figcaption></figure>

## Warnings

If a logger encounters an issue that requires the user’s attention, it will be highlighted in yellow (the device is operating, but the issue should be addressed) or in red (the device is not operating correctly and immediate action is required) in the mobile application’s device list. The application may display the following warnings:

**Low battery level** – shown as a yellow battery icon next to the logger’s name. After this icon appears, the battery should be [replaced](/efento-ble-loggers/installation/replacing-the-battery.md) within approximately 30 days. Stored measurement data will not be lost, and you will be able to read them after replacing the battery.

<figure><img src="/files/IgCzc8mIp0wjP6HT0IGF" alt="" width="375"><figcaption></figcaption></figure>

**Sensor not calibrated / calibration in progress** – Some sensors (e.g., IAQ, CO₂) require manual or automatic calibration to ensure high-accuracy measurements. If a device needs calibration or is currently performing automatic calibration, this information will appear below the sensor’s serial number.

<figure><img src="/files/ALFXFAk6qf45364sM2K3" alt="" width="375"><figcaption></figcaption></figure>

**Synchronization required** – This message appears for pulse counters that have not had their initial value set or were restarted during operation. As a result, the values they report may be incorrect. The warning is shown in yellow beneath the device’s serial number.

<figure><img src="/files/AtpWs9u5ELiteChzmiXH" alt="" width="375"><figcaption></figcaption></figure>

**Sensor defective** – a red indicator appears next to the sensor's name along with the message *“sensor defective”* under the serial number. This means the logger is unable to take valid measurements (values are out of range or unavailable). For sensors with external probes, this issue is most often caused by a disconnected or physically damaged probe.

<figure><img src="/files/5WfAcLXuQGOvg6aaXUNR" alt="" width="375"><figcaption></figcaption></figure>

**Device error** – A general error indicating a problem with the sensor’s operation. Please contact our support team at [help.efento.io](https://help.efento.io) for diagnostics and assistance.

<figure><img src="/files/4y7PIMuWcgsLCyd0RBU7" alt="" width="375"><figcaption></figcaption></figure>

**Firmware update available** – if a new firmware version is available, the information will appear below the logger’s name and serial number. To update the firmware, tap the logger on the list and enter its PIN code (located on the device’s enclosure label).

<figure><img src="/files/q5aaGJKo25AOrrsEhtSH" alt="" width="360"><figcaption></figcaption></figure>


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