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.

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.

Create a LabJack read task

In the devices toolbar, right-click the device and select Create read task.
Set Sample rate and Stream rate.
Click Add channel, then select the type of channel and the Port.
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.

Python does not create channels. Create them first.

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 does not create channels. Create them first.

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.

In the channel list, click Tare on an analog channel. To tare several channels, select them, right-click, and select Tare.
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.
Data saving	`data_saving_disabled`	On	See 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

Digital input

Thermocouple

Analog input

Python AnalogReadChannelTypeScript 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

Python DigitalReadChannelTypeScript digital

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

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

Thermocouple

Python ThermocoupleReadChannelTypeScript 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
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.
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
Cause
Two channels use the same port.
Fix
Select a different port for one of them.

For other problems, see Configure a LabJack device and Troubleshoot hardware.

Configure a device

Write task