---
title: "Line start (line trigger)"
slug: "set-line-trigger"
updated: 2024-01-12T21:28:40Z
published: 2024-01-12T21:28:40Z
canonical: "docs-linescan.alliedvision.com/set-line-trigger"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://docs-linescan.alliedvision.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Set a line trigger

## Internal line trigger

The internal line trigger provides a continuous signal in the frequency of the exposure time.

| 1. In the Configuration window navigate to *Acquisition Control* → *Line* *Trigger*. 2. Below *Internal* select the **Generate line trigger at frequency of line rate** checkbox. | ![Ein Bild, das Text enthält. Automatisch generierte Beschreibung](https://cdn.document360.io/eca58697-9c2f-461e-9f0a-e6205b74b693/Images/Documentation/camera-features-image-ylc5jfd9.png) |
| --- | --- |

Alternatively, you can set the internal line trigger in the camera feature tree by executing the following step:

| Step | Feature name | Value |
| --- | --- | --- |
| 1 | Trigger Selector | LineStart |
| Trigger Mode | Off |

## External line trigger

The external line trigger can be provided by an encoder signal or a signal generator. Refer to [Trigger Selector](/v1/docs/set-line-trigger#trigger-selector).

1. In the Configuration window navigate to *Acquisition Control* → *Line* *Trigger*.
2. Below *External* select the **Generate line trigger from external encoder signal** checkbox.

| 1. In *Encoder Source A* and *B* select the desired input Line. Refer to [electrical installation](/v1/docs/evo-electrical-installation#digital-io-port). 2. In *Line Format* select the electrical input signal. Refer to [electrical installation](/v1/docs/evo-electrical-installation#digital-io-port). 3. In *Encoder Divider float* input the number of encoder impulses to generate one *LineStart* signal. Refer to [Encoder divider float](/v1/docs/set-line-trigger#encoder-divider-float). 4. In *Encoder Average* input the number of averaged input signals. | ![](https://cdn.document360.io/eca58697-9c2f-461e-9f0a-e6205b74b693/Images/Documentation/linetrigger_encoder(2).PNG) |
| --- | --- |

Alternatively, you can set the external line trigger in the camera feature tree by executing the following steps:

| Step | Feature name | Value |
| --- | --- | --- |
| 1 | TriggerSelector | LineStart |
| TriggerMode | On |
| 2 | TriggerSource | Encoder0 **or** Line1 **or** Line3 **or** Line4 |
| 3 | EncoderSelector | Encoder0 |
| 4 | EncoderSource A | Line1 |
| 5 | EncoderSource B | Line2 |
| 6 | EncoderDividerFloat | 0.05 – 255 |
| 7 | EncoderAverage | 0-16 |
| 8 | Digital I/O Line Selector | select the Trigger Source |
| 9 | Line Format | open the drop-down menu and change the Line Format to your input signal |

### Trigger Selector

#### Encoder0

The *Trigger Source → Encoder0* triggers the *LineStart* of the image acquisition. A certain number of encoder (Encoder divider float) impulses creates one *LineStart* signal.

![svg-signal diagram-encoder 2 channel_03](https://cdn.document360.io/eca58697-9c2f-461e-9f0a-e6205b74b693/Images/Documentation/svg-signal%20diagram-encoder%202%20channel_03.svg)

#### Line

The *Trigger Source → Line* triggers the *LineStart* of the image acquisition. Each impulse generates one *LineStart* signal.

![svg-signal diagram-wave_03](https://cdn.document360.io/eca58697-9c2f-461e-9f0a-e6205b74b693/Images/Documentation/svg-signal%20diagram-wave_03.svg)

### Encoder divider float

An encoder typically does not have an integer ratio to the camera resolution. Arbitrary ratios of encoder pulses per sensor line are possible, for example, 2.25. The value range is 0.05 – 255 pulses per line.

**Example**

- Linear Stage with a tread pitch of 1 mm
- Encoder with a resolution of 1000 Impulses per turnaround (I/U) → 1 Impuls per µm
- Optical lateral Camera resolution of 10 µm

Encoder divider float = Optical resolution × encoder transport resolution = 10 µm × 1 I/µm = 10 I $\approx$