# Connecting an Instrument

In **Live** mode, COM Agent reads measurement data directly from an instrument over a serial (COM) connection.

<!-- docshot: connection crop=.config -->
![](../_images/com-agent-connection.png)

## 1. Connect the hardware

1. Connect the instrument to the PC using its serial cable or USB-to-serial adapter. Some instruments (CBT1.2, NovoHaze TX) require a special cable — see the [overview](rhopoint-com-agent.md).
2. Switch the instrument on.

## 2. Choose the connection settings

In the **Connection** section on the left:

| Setting | Description |
| --- | --- |
| **Mode** | Set to **Live** to read from a serial port. (Use **Demo** to try the app without hardware — see [Demo Mode](rhopoint-com-agent-demo-mode.md).) |
| **COM Port** | Select the port your instrument is connected to. Click the **refresh** button to re-scan for ports after plugging in an adapter. |
| **Baud Rate** | The serial speed. The default for Rhopoint instruments is **19200**. |
| **Part Marker** | The character the instrument prints to mark each part of a complete data set. The default is **^**. |
| **Part Count** | How many part markers make up one complete data set. The default is **4**. |

> [!info] **Part Marker** and **Part Count** tell COM Agent when a measurement is complete. A data set is written out only once the expected number of markers has been received and the line ends — this prevents half-received measurements from being saved. The defaults match Rhopoint instruments; only change them if advised by Rhopoint Support.

## 3. Choose what to do with the data

Decide how each measurement should be saved or forwarded:

- Write files — see [Output Formats](rhopoint-com-agent-output-formats.md).
- Type values into another application — see [Keyboard Emulation](rhopoint-com-agent-keyboard-emulation.md).

You can combine these (for example, write a CSV file *and* type the mean into a spreadsheet).

## 4. Start capturing

Press **Start** (top right) and take a measurement on the instrument. The activity log on the right confirms data is arriving. See [Capturing Measurements](rhopoint-com-agent-capturing-measurements.md) for details.

> [!warning] If the selected COM port cannot be opened (for example, because another program is already using it), COM Agent shows an error. Close the other program or pick a different port, then try again.

[Next: choose your output format](rhopoint-com-agent-output-formats.md)