> For the complete documentation index, see [llms.txt](https://help.boomerang3.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.boomerang3.com/boomerang-3-calibration-app-manual/calibration-set/reference-thermometers/wlref.md).

# WLREF

WLREF thermometer is equiped with one high-accuracy digital temperature sensor. 

It has the following parameters:

<table><thead><tr><th width="182">Parameter</th><th>Value</th><th>Comments</th></tr></thead><tbody><tr><td>Accuracy with no calibration</td><td>±0.1°C from –20°C to +50°C
<br>±0.15°C from –40°C to +70°C
<br>±0.2°C from –40°C to +100°C
<br>±0.25°C from –55°C to +125°C
<br>±0.3°C from –55°C to +150°C</td><td></td></tr><tr><td>Measuring range</td><td>-80 to +150°C</td><td></td></tr><tr><td>Resolution</td><td>0.0078125°C</td><td></td></tr><tr><td>Hysteresis</td><td>±0.015625°C</td><td></td></tr><tr><td>Repeatability</td><td>±0.0078125°C</td><td></td></tr><tr><td>Long term stability</td><td>±0.03°C</td><td>Aging for 300 hours at 150°C</td></tr><tr><td>Battery</td><td>CR2477N</td><td>Recommended type is <a href="https://www.tme.eu/pl/en/details/bat-cr2477ht_a/batteries/akyga-battery/aky1048/">https://www.tme.eu/pl/en/details/bat-cr2477ht_a/batteries/akyga-battery/aky1048/</a></td></tr></tbody></table>

WLREF communicates with Cal App using Bluetooth Low Energy radio connection and has a typical open air communication range of 10m.

To preserve the battery the WLREF thermometer stays in sleep mode and wakes automatically only to measure the temperature once a minute. It has a single push button to wake it up when the Cal App needs to contact it. The button is used for reference meter assigning, calibration start and data reading. The red LED inside the case stays on when WLREF is active. There is also green LED which blinks when data are sent via Bluetooth.

The battery shall be replaced when its voltage drops below 2.8V. When the  battery level is too low, WLREF will deliver only few of 10 readings it shall send to the Cal App.

<img src="/files/mfd3QT4m58uEko2ej97R" alt="" width="335">


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