# Define B3 sensor for calibration

For B3 automatic calibration a dialog is opened to select the Boomerang 3 sensor that will be calibrated. 

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You may search for a specific name using the field on top of the dialog.

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Tap the sensor you want to calibrate. A form is opened to enter the serial number and resolution of the sensor to calibrate. The form contains also the environment conditions.&#x20;

The serial number is stated on the sensor label. Some of the fields may be filled in automatically, basing on B3 settings available for a given MP.

In "Calibrated sensor resolution" select the correct sensor type or select "Custom" and enter the resolution manually. The detailed information about sensor resolutions can be found in [calibrated-sensor-resolution](https://help.boomerang3.com/boomerang-3-calibration-app-manual/advanced/calibrated-sensor-resolution "mention") chapter.

Enter the delay (min. 0 min) and the total time which is delay plus 11 min. (min. 11 min).

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Tap “OK” to start the calibration.\
The app will communicate with Boomerang 3 server to initiate the calibration process.

In case of WLREF sensor, press its button to wake it up as the Cal App must send a command to initiate the measurements. After initiation, WLREF will start measuring every minute and will store the readings in its internal memory.

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Next follow the steps described in [calibration-run](https://help.boomerang3.com/boomerang-3-calibration-app-manual/performing-the-calibration/calibration-run "mention").