> For the complete documentation index, see [llms.txt](https://docs.simplephysx.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.simplephysx.com/readme/getting-started.md).

# First device in the UI

Create one temperature sensor in the browser and verify a 31.25 degree readback.

## Before you start <a href="#first-device-in-the-ui" id="first-device-in-the-ui"></a>

Use the [SPX 1.1.0 stable bundle](/operations-and-support/release-notes.md): installer **1.1.0**, Server **1.0.0** and UI **1.1.0**. This is the same first result linked from the website's Getting Started page.

**Prerequisites:** [SPX installed](/readme/installation-guide.md), UI open at `http://localhost:3000`. In [Settings](/reference/ui-reference/settings.md), confirm **Ready**, the intended upstream target and **Authorization: Accepted by SPX server**. SPX Setup manages this connection. To change it, rerun Setup and start the updated environment, then use **Retry** in Settings.

**Result:** instance `my_temperature_sensor` is **RUNNING**; setting its input to **31.25°C** produces a telemetry reading of **31.25°C**. No MCP, Python or external protocol client is needed. This is a simulation exercise, not a hardware check.

**Start with** [**Create and control an instance**](/spx-development-guide/ui/ui-instance.md)**.** That is the main walkthrough: load the supplied model file, create the sensor, start it and verify the temperature. Then keep it running and continue directly with [Connect two instances](/spx-development-guide/ui/connect-instances.md).

If you prefer to paste YAML instead of downloading a file, use the alternative below to prepare the same model, then join the main walkthrough at step 2.

## Create the model <a href="#create-the-model" id="create-the-model"></a>

This is an alternative to step 1 of the main walkthrough. Use it before creating the sensor; if you already completed the walkthrough, continue to connections.

1. Open **Models → New model**. In the new Model View, choose **Edit model name**, enter `my_temperature_model` and save the name. Use a fresh exercise environment if that name already belongs to another model.
2. Select YAML in the editor and paste the complete definition below.
3. Choose **Create model** and check the Validation panel for **OK**.

```yaml
name: pt100_demo
description: Minimal deterministic temperature sensor
attributes:
  k__temperature_c:
    type: float
    default: 20.0
    unit: degC
  temperature_c:
    type: float
    default: 20.0
    unit: degC
actions:
  - function: $in(temperature_c)
    name: update_temperature
    call: $in(k__temperature_c)
```

The definition's `name` is metadata; the registry name you saved is the model selected when creating an instance. See [model identifiers](/reference/glossary-of-terms.md#model-identifiers) if these names differ in your project.

## Create and start an instance

Continue at **step 2: Create an instance** in [Create and control an instance](/spx-development-guide/ui/ui-instance.md). Your model is already saved, so skip its file-loading step. Follow steps 2–3 to create and start `my_temperature_sensor`.

## Change an input and verify the result

In step 4 of that walkthrough, set `k__temperature_c` to **31.25** and verify that `temperature_c` follows to **31.25**. A successful edit alone does not prove that the model processed the input; check the telemetry readback.

## Finish and continue

Keep `my_temperature_sensor` running for [Connect two instances](/spx-development-guide/ui/connect-instances.md); both ways of preparing the model lead to that exercise. If you are finishing here, stop the sensor. To remove the exercise, delete its instance and then `my_temperature_model`. The [UI guide path](/spx-development-guide/ui.md) lists the later exercises.