LabJack Read Task
Learn how to acquire data from LabJack devices with Synnax.
For task lifecycle management, see the Task Basics page.
Task Configuration Reference
Channel Types Reference
Analog Input (AI)
AI)Reads analog voltage from a specified input terminal. Supports single-ended and differential configurations.
Thermocouple (TC)
TC)Reads temperature from a thermocouple with cold junction compensation (CJC).
Performance Note -> Thermocouple channels use LabJack’s built-in thermocouple features, which reduce the maximum reliable sample rate compared to tasks with only analog or digital inputs.
CJC Configuration Examples:
- Device temp sensor ->
cjc_source="TEMPERATURE_DEVICE_K",cjc_slope=1.0,cjc_offset=0.0 - LM34 sensor ->
cjc_source="AIN1",cjc_slope=55.56,cjc_offset=255.37
Digital Input (DI)
DI)Reads digital state (0 or 1) from a specified digital I/O line.
Important Rules
- Sample rates -> All channels in a task sample at the same rate. Create separate tasks for different rates.
- Thermocouple performance -> Tasks with thermocouple channels have reduced maximum sample rates due to LJM thermocouple processing.
- One running task per channel -> A channel can only receive live data from one task at a time.
- Stream rate optimization -> For low-rate tasks (< 50 Hz), set the stream rate to the sample rate. For high-rate tasks, keep stream rate less than 50 Hz for better performance.
How-To
Configure and run task
import synnax as sy
from synnax import labjack
client = sy.Synnax()
# Retrieve device
dev = client.devices.retrieve(name="my_labjack")
# Create index channel
ai_time = client.channels.create(
name="ai_time",
is_index=True,
data_type=sy.DataType.TIMESTAMP,
retrieve_if_name_exists=True,
)
# Create data channels
ai_0 = client.channels.create(
name="ai_0",
index=ai_time.key,
data_type=sy.DataType.FLOAT32,
retrieve_if_name_exists=True,
)
ai_1 = client.channels.create(
name="ai_1",
index=ai_time.key,
data_type=sy.DataType.FLOAT32,
retrieve_if_name_exists=True,
)
di_4 = client.channels.create(
name="di_4",
index=ai_time.key,
data_type=sy.DataType.UINT8,
retrieve_if_name_exists=True,
)
# Create and configure task
task = labjack.ReadTask(
name="LabJack Read Task",
device=dev.key,
sample_rate=sy.Rate.HZ * 100,
stream_rate=sy.Rate.HZ * 25,
data_saving=True,
channels=[
labjack.AIChan(
channel=ai_0.key,
port="AIN0",
range=10.0,
neg_chan=199, # Single-ended
pos_chan=0,
),
labjack.AIChan(
channel=ai_1.key,
port="AIN1",
range=10.0,
neg_chan=199, # Single-ended
pos_chan=1,
),
labjack.DIChan(
channel=di_4.key,
port="DIO4",
),
],
)
client.tasks.configure(task)
# Start task and read data
with task.run():
with client.open_streamer(["ai_0", "ai_1", "di_4"]) as streamer:
for _ in range(10):
frame = streamer.read()
print(frame) Edit task configuration
# Retrieve existing task
task = client.tasks.retrieve(name="LabJack Read Task")
task = labjack.ReadTask(internal=task)
# Update task-level configuration
task.config.auto_start = True
task.config.stream_rate = int(sy.Rate.HZ * 50)
# Update first analog input configuration
task.config.channels[0].port = "AIN2"
task.config.channels[0].range = 5.0
# Update second analog input configuration
task.config.channels[1].port = "AIN3"
task.config.channels[1].range = 1.0
# Update digital input configuration
task.config.channels[2].port = "DIO5"
# Apply changes
client.tasks.configure(task) Configure and run task
import { Synnax } from "@synnaxlabs/client";
const client = new Synnax();
// Retrieve device
const dev = await client.devices.retrieve({ name: "my_labjack" });
// Create index channel
const aiTime = await client.channels.create({
name: "ai_time",
isIndex: true,
dataType: "timestamp",
retrieveIfNameExists: true,
});
// Create data channels
const ai0 = await client.channels.create({
name: "ai_0",
index: aiTime.key,
dataType: "float32",
retrieveIfNameExists: true,
});
const ai1 = await client.channels.create({
name: "ai_1",
index: aiTime.key,
dataType: "float32",
retrieveIfNameExists: true,
});
const di4 = await client.channels.create({
name: "di_4",
index: aiTime.key,
dataType: "uint8",
retrieveIfNameExists: true,
});
// Create and configure task
const task = await client.tasks.create({
name: "LabJack Read Task",
type: "labjack_read",
config: JSON.stringify({
device: dev.key,
sample_rate: 100,
stream_rate: 25,
data_saving: true,
channels: [
{
type: "AI",
channel: ai0.key,
port: "AIN0",
range: 10.0,
neg_chan: 199,
pos_chan: 0,
},
{
type: "AI",
channel: ai1.key,
port: "AIN1",
range: 10.0,
neg_chan: 199,
pos_chan: 1,
},
{
type: "DI",
channel: di4.key,
port: "DIO4",
},
],
}),
});
// Start task
await task.executeCommandSync("start");
// Read data
const streamer = await client.openStreamer(["ai_0", "ai_1", "di_4"]);
for (let i = 0; i < 10; i++) {
const frame = await streamer.read();
console.log(frame);
}
// Stop task
await task.executeCommandSync("stop");
await streamer.close(); Edit task configuration
// Retrieve existing task
const task = await client.tasks.retrieve({ name: "LabJack Read Task" });
// Parse and update configuration
const config = JSON.parse(task.config);
// Update task-level configuration
config.auto_start = true;
config.stream_rate = 50;
// Update first analog input configuration
config.channels[0].port = "AIN2";
config.channels[0].range = 5.0;
// Update second analog input configuration
config.channels[1].port = "AIN3";
config.channels[1].range = 1.0;
// Update digital input configuration
config.channels[2].port = "DIO5";
// Apply changes
await client.tasks.create({
key: task.key,
name: task.name,
type: task.type,
config: JSON.stringify(config),
});