# Bluetooth Operation
### Bluetooth Bonding to a RAPT Device
To use the Bluetooth functionality of the RAPT Bluetooth Thermometer you will need to **Bond** it via Bluetooth to a RAPT Temperature Controller, RAPT Fermentation Chamber or Gen 4 BrewZilla Controller. Follow the steps below to bond your RAPT Bluetooth Thermometer to a RAPT enabled device:
1. Bluetooth needs to first be enabled in the **Settings** menu. Use the **Up** or **Down** buttons to scroll to select the **Settings** menu. Scroll to Bluetooth and choose **Select** button to Enable Bluetooth, or the **Return** button to cancel if Bluetooth is already enabled.
2. To **Bond** a RAPT Bluetooth Thermometers, use the **Up** or **Down** buttons to scroll to select the device - displayed as **RAPT Temp \[Temperature]**. Choose **Select** button to **Bond** the device, or the **Return** button to cancel.
Once **Bonded**, the device will be visible in the **Bonded** section of the **Bluetooth Menu**. To **Unbond**, select the device with the navigation arrows and choose **Select** buttont to **Unbond** the device, or the **Return** button to cancel.
You can successfully bond multiple RAPT Bluetooth Thermometers with your RAPT enabled controller in this way. Each RAPT Bluetooth Thermometer has a unique MAC address which is displayed in the Bluetooth settings when the thermometer is powered on.
### Setting the RAPT Bluetooth Thermometer to be the controlling temperature sensor
The RAPT Bluetooth Thermometer can be set as the controlling temperature sensor of your RAPT Controller. To set the RAPT Bluetooth Thermometer as the controlling temperature sensor follow the instructions below.
1. [Bond the RAPT Bluetooth Thermometer](#bluetooth-bonding-to-a-rapt-device) to your RAPT Temperature Controller, RAPT Fermentation Chamber or Gen 4 BrewZilla Controller
2. Use the **Up** or **Down** buttons to scroll to select the **Settings** menu on the RAPT Temperature Controller, RAPT Fermentation Chamber or Gen 4 BrewZilla Controller
3. Select **Temperature Senso**r and choose **Select** . Use the **Up** or **Down** buttons to scroll through the available Bluetooth Bonded devices untilthe desired RAPT Bluetooth Thermometer is selected. Choose **Select** to confirm the setting of the RAPT Bluetooth Thermometer as the controlling temperature sensor
Once you have set the RAPT Bluetooth Thermometer as the controller temperature sensor your RAPT Temperature Controller, RAPT Fermentation Chamber or Gen 4 BrewZilla will then cycle the heating or cooling (if applicable) on, **according to the temperature measured by the RAPT Bluetooth Thermometer and not by the built-in probe on the RAPT Controller or BrewZilla.**
### Using the RAPT Bluetooth Thermometer to measure and control mash temperature
The RAPT Bluetooth Thermometer can be utilised to achieve a more accurate mash temperature during your brew day.
To really nail your mash temperature, measure the core temperature of the mash and set the RAPT Bluetooth Thermometer to be the controlling temperature sensor for the BrewZilla.
When the RAPT Bluetooth Thermometer is set as the controlling temperature sensor the elements will turn On/Off when required based on the set temperature on the controller and the temperature measured by the RAPT Bluetooth Thermometer within the core of the mash.
This allows a more accurate mash temperature to be maintained and meaning you can nail your recipe, increase the response time for a step mash or mash out and improve efficiency.
1. Bond the RAPT Bluetooth Thermometer to your BrewZilla Controller
2. Set the RAPT Bluetooth Thermometer as the controlling temperature sensor
3. Set your required mash temperature, Sensor Differential and Power on your BrewZilla controller
4. Insert the probe of the RAPT Bluetooth Thermometer into your mash. **IMPORTANT**: Use the included top screen to hold the probe in the correct position
For a comprehensive guide to using your RAPT Bluetooth Thermometer with a RAPT Gen 4 BrewZilla, please refer to [**Using the RAPT Bluetooth Thermometer**](/equipment/rapt-brewzilla-or-user-guide/using-the-rapt-bluetooth-thermometer.md) and also [**Advanced Profile Operation**](/equipment/rapt-brewzilla-or-user-guide/using-the-rapt-bluetooth-thermometer.md#advanced-profile-operation)
### Using the RAPT Bluetooth Thermometer to measure and control distillation
The RAPT Bluetooth Thermometer is also a useful tool for monitoring the head temperature of your distillation apparatus and subsequently controlling your boiler based on the temperature in the still head and automating the overall distillation process.
To achieve this simply insert the probe into the thermowell in your distillation apparatus. Then bond your RAPT Bluetooth Thermometer with your Gen 4 BrewZilla and set the thermometer to be the controlling temperature sensor.
Adjust the set temperature of the Gen 4 BrewZilla to be when you want the distillation to end (for example the temperature that you expect to begin collecting tails). Then once the temperature in the still head hits this shut off temperature the BrewZilla will then turn off the heating elements until the temperature drops below the hysteresis value set on your BrewZilla.
You may need to adjust the **Allowed Sensor Diff.** setting in the BrewZilla controller to ensure that the wash in your boiler continues boiling throughout the distillation process.
### Allowed Sensor Differential
The **Allowed Sensor Diff.** setting in the RAPT Controller is the maximum deviation (differential) from the set point temperature that the built-in temperature probe of the bonded RAPT enabled device is allowed to reach before the heating/cooling is turned off to prevent excessive temperature over/undershoot.
The heating/cooling of the RAPT Controller will then turn back on based on the hysteresis settings of the controller to increase or decrease the measured temperature until it reaches the desired set point.
Thus, with a set point temperature of 65°C, and an **Allowed Sensor Diff** of 5°C (using typical mash temperatures on a BrewZilla as an example), the elements will operate up to 70°C - which is 5°C above the set point.
However, the elements will shut off when the RAPT Bluetooth Thermometer reaches the set point temperature of 65°C
As a guide, setting a smaller **Allowed Sensor Diff** for mainating temperature and a larger **Allowed Sensor Diff** for increasing the temperature of the mash is a good approach. Refer to [**Using the RAPT Bluetooth Thermometer**](/equipment/rapt-brewzilla-or-user-guide/using-the-rapt-bluetooth-thermometer.md) and also [**Advanced Profile Operation**](/equipment/rapt-brewzilla-or-user-guide/using-the-rapt-bluetooth-thermometer.md#advanced-profile-operation) for more information.
More detailed information regarding how the **Allowed Sensor Diff.** setting works can be found in the video below
{% embed url="" %}
{% embed url="" %}
---
# Agent Instructions: Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.
Perform an HTTP GET request on the current page URL with the `ask` query parameter:
```
GET https://docs.rapt.io/equipment/rapt-bluetooth-thermometer-or-user-guide/bluetooth-operation.md?ask=
```
The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.
or **Down** 
buttons to scroll to select the **Settings** menu. Scroll to Bluetooth and choose **Select** 
button to Enable Bluetooth, or the **Return** 
button to cancel if Bluetooth is already enabled.
2. To **Bond** a RAPT Bluetooth Thermometers, use the **Up**