# LabJack read task

> Read analog, digital, and thermocouple inputs from a LabJack into channels.

A LabJack read task reads the inputs of one LabJack device into channels. For example, it can record a pressure transducer on `AIN0` and a switch on `DIO4` at 1 kHz.

Before you start, you need a [configured device](https://docs.synnaxlabs.com/reference/hardware/labjack/configure-device).

## Channels and timing

A read task has three types of channels:

* **Analog input** -> a voltage on an `AIN` port.
* **Digital input** -> the state of a `DIO` port, as 0 or 1.
* **Thermocouple** -> a temperature from a thermocouple on an `AIN` port. Thermocouples work on the T7 only.

With no thermocouple channels, the device samples the inputs on its own clock. With one or more thermocouple channels, the Driver reads one sample of each channel at a time, and the **Stream rate** has no effect. See [timing](https://docs.synnaxlabs.com/reference/hardware/tasks#timing).

## Create a LabJack read task

[Enterprise](https://docs.synnaxlabs.com/reference/get-started/editions "Needs Synnax Enterprise")

**Console**

1. In the devices toolbar, right-click the device and select **Create read task**.
2. Set **Sample rate** and **Stream rate**.
3. Click **Add channel**, then select the type of channel and the **Port**.
4. Click (**Start**).

The Console creates the channels. For a device with the identifier `lj1`, the channel for `AIN0` is `lj1_AIN0`, with the index channel `lj1_time`. To use a different name, enter it in the channel list before you start the task.

[](https://synnax.nyc3.cdn.digitaloceanspaces.com/docs/hardware/labjack/read-task-dark.mp4#t=0.001)

**Python**

Python does not create channels. Create them first.

```python
import synnax as sy
from synnax import labjack

dev = client.devices.retrieve(key="<serial number>")
time = client.channels.create(
    name="lj1_time", is_index=True, data_type=sy.DataType.TIMESTAMP
)
pressure = client.channels.create(
    name="lj1_AIN0", index=time.key, data_type=sy.DataType.FLOAT32
)
switch = client.channels.create(
    name="lj1_DIO4", index=time.key, data_type=sy.DataType.UINT8
)

task = labjack.ReadTask(
    name="Test stand inputs",
    device=dev.key,
    sample_rate=1000,
    stream_rate=25,
    channels=[
        labjack.AnalogReadChannel(port="AIN0", channel=pressure.key),
        labjack.DigitalReadChannel(port="DIO4", channel=switch.key),
    ],
)
client.tasks.configure(task)
task.start()
```

Python creates the task on the embedded Driver of the Core. For a device on another Driver, use the Console or TypeScript.

For a thermocouple on a T7, use `labjack.ThermocoupleReadChannel(port="AIN2", thermocouple_type="K", units="C", channel=...)`.

**TypeScript**

TypeScript does not create channels. Create them first.

```typescript
import { labjack } from "@synnaxlabs/client";

const dev = await client.devices.retrieve({ key: "<serial number>" });
const time = await client.channels.create({
  name: "lj1_time",
  isIndex: true,
  dataType: "timestamp",
});
const pressure = await client.channels.create({
  name: "lj1_AIN0",
  index: time.key,
  dataType: "float32",
});

const task = await client.tasks.create({
  name: "Test stand inputs",
  rack: dev.rack,
  type: "labjack_read",
  config: labjack.readConfigZ.parse({
    device: dev.key,
    sampleRate: 1000,
    streamRate: 25,
    channels: [{ type: "analog", port: "AIN0", channel: pressure.key }],
  }),
});
await task.start();
```

## Tare channels

Tare sets the current value of an analog channel to zero. The task must be running.

1. In the channel list, click **Tare** on an analog channel. To tare several channels, select them, right-click, and select **Tare**.
2. The values of those channels start from zero.

## Task options

| Console label | Python field           | Default | Notes                                                                                |
| ------------- | ---------------------- | ------- | ------------------------------------------------------------------------------------ |
| Device        | `device`               |         | The serial number of the device.                                                     |
| Sample rate   | `sample_rate`          | 10 Hz   | Up to 50,000 Hz in the Console.                                                      |
| Stream rate   | `stream_rate`          | 5 Hz    | See [read tasks](https://docs.synnaxlabs.com/reference/hardware/tasks#read-tasks).   |
| Data saving   | `data_saving_disabled` | On      | See [data saving](https://docs.synnaxlabs.com/reference/hardware/tasks#data-saving). |
| Auto start    | `auto_start`           | Off     | Starts the task each time the Driver starts.                                         |

## Channel reference

Each channel has a `channel`, the Synnax channel that records the value. Each table shows the Console label of a setting, with its Python field under it.

**Analog input**

#### [Analog input](https://docs.synnaxlabs.com/reference/hardware/labjack/read-task#analog)

Python `AnalogReadChannel`TypeScript `analog`

Reads a voltage.

| Setting             | Default | Notes                                                                                          |
| ------------------- | ------- | ---------------------------------------------------------------------------------------------- |
| Port `port`         | `AIN0`  | An `AIN` port.                                                                                 |
| Max voltage `range` | `10`    | The Driver does not apply this field. Each input uses the default range of the device.         |
| `neg_chan`          | `199`   | The negative input for a differential reading, on the T7 only. 199 means a single-ended input. |
| Scale `scale`       | None    | None, linear (slope and offset), or map (from a raw range to a scaled range).                  |

**Digital input**

#### [Digital input](https://docs.synnaxlabs.com/reference/hardware/labjack/read-task#digital)

Python `DigitalReadChannel`TypeScript `digital`

Reads the state of a digital line as 0 or 1, as `uint8`.

| Setting     | Default | Notes         |
| ----------- | ------- | ------------- |
| Port `port` | `DIO4`  | A `DIO` port. |

**Thermocouple**

#### [Thermocouple](https://docs.synnaxlabs.com/reference/hardware/labjack/read-task#thermocouple)

Python `ThermocoupleReadChannel`TypeScript `thermocouple`

Reads a temperature from a thermocouple.

| Setting                               | Default                | Notes                                                    |
| ------------------------------------- | ---------------------- | -------------------------------------------------------- |
| Port `port`                           | `AIN0`                 | An `AIN` port.                                           |
| Thermocouple type `thermocouple_type` | `K`                    | `B`, `E`, `J`, `K`, `N`, `R`, `S`, `T`, `C`.             |
| Temperature units `units`             | `K`                    | `C`, `F`, `K`.                                           |
| Negative channel `neg_chan`           | `199`                  | The negative input. 199 means a single-ended input.      |
| CJC source `cjc_source`               | `TEMPERATURE_DEVICE_K` | **Device**, **Air**, or an `AIN` port with a CJC sensor. |
| CJC slope `cjc_slope`                 | `1`                    | The CJC sensor scale, in kelvin per volt.                |
| CJC offset `cjc_offset`               | `0`                    | The CJC sensor offset, in kelvin.                        |
| Scale `scale`                         | None                   | Applied after the conversion to temperature.             |

## Troubleshooting

* [Falling behind hardware](https://docs.synnaxlabs.com/reference/hardware/labjack/read-task#falling-behind-hardware)

  * Cause

    The Driver cannot send the samples as fast as the device makes them.

  * Fix

    Lower the **Stream rate**, or lower the **Sample rate**.

* [Thermocouple values are wrong.](https://docs.synnaxlabs.com/reference/hardware/labjack/read-task#thermocouple-values-are-wrong)

  * Cause

    The device is not a T7. The Driver sets up thermocouples on the T7 only.

  * Fix

    Use a T7 for thermocouple channels.

* [Port ... has already been used on another channel](https://docs.synnaxlabs.com/reference/hardware/labjack/read-task#port-has-already-been-used-on-another-channel)

  * Cause

    Two channels use the same port.

  * Fix

    Select a different port for one of them.

For other problems, see [Configure a LabJack device](https://docs.synnaxlabs.com/reference/hardware/labjack/configure-device#troubleshooting) and [Troubleshoot hardware](https://docs.synnaxlabs.com/reference/hardware/troubleshooting).