NI DAQ Setup

V-Listen supports National Instruments data acquisition hardware through the NI-DAQmx driver framework. This enables high-channel-count measurements with a wide range of signal conditioning options including voltage, IEPE, and pressure inputs. The NI adapter integrates device discovery, channel configuration, trigger setup, and synchronized multi-device acquisition.

Prerequisites

NI-DAQmx Driver — version 2021 or later must be installed. Download from the NI website or install via NI Package Manager.
NI MAX — use NI Measurement & Automation Explorer to verify that the device is recognized and to perform self-tests before using V-Listen.
Device firmware — ensure the DAQ device firmware is up to date, especially for USB and cDAQ devices.

Device Selection

When you open Acquisition → NI DAQ, V-Listen enumerates all NI-DAQmx compatible devices connected to the system. The device list shows:

Field	Description
Device Name	NI-DAQmx device alias (e.g., "cDAQ1Mod1", "Dev1")
Product Type	Hardware model (e.g., "NI 9234", "NI USB-4431")
Serial Number	Unique hardware identifier
Max Sample Rate	Maximum aggregate sampling rate
Channel Count	Number of analog input channels

For cDAQ chassis systems, each module appears as a separate device. V-Listen supports multi-module synchronized acquisition within the same chassis automatically.

Channel Types

Voltage Input

Direct voltage measurement with configurable range. Suitable for sensors with external signal conditioning or voltage-output transducers.

Parameter	Options
Terminal Configuration	Differential / RSE / NRSE / Pseudodifferential
Voltage Range	±0.2 V to ±10 V (device-dependent)
Coupling	DC / AC

IEPE Input

For accelerometers and microphones with integrated electronics. The DAQ module provides constant-current excitation (typically 2–4 mA) and AC coupling.

Parameter	Options
Excitation Current	0 – 4 mA (module-dependent)
Sensitivity	User-defined (mV/g, mV/Pa, etc.)
Coupling	AC (mandatory for IEPE)

The NI 9234 and NI USB-4431 are the recommended modules for IEPE-based acoustic and vibration measurements. They provide 24-bit resolution with built-in anti-aliasing filters and IEPE current source.

Pressure Input

For piezoresistive and capacitive pressure transducers requiring bridge excitation. Available on bridge-capable modules (e.g., NI 9237).

Trigger Configuration

Triggers control when data acquisition starts and stops. V-Listen supports the following trigger modes:

Trigger Mode	Description	Use Case
Immediate	Recording starts as soon as Record is clicked.	Manual measurements, continuous monitoring
Analog Edge	Starts when a channel crosses a threshold level with specified slope (rising/falling).	Impact testing, event-triggered capture
Digital Edge	Starts on a digital trigger signal (PFI line).	Synchronized multi-system measurements
Software	Recording starts on a programmatic trigger from V-Listen.	Automated test sequences

Trigger Parameters

Parameter	Description
Source Channel	The analog or digital channel used as trigger source.
Level	Threshold value in engineering units.
Slope	Rising or falling edge.
Pre-trigger Samples	Number of samples to retain before the trigger event.
Hysteresis	Prevents re-triggering on noisy signals.

Sampling Rate Configuration

The sampling rate determines the maximum analysis bandwidth and is shared across all channels within a task. Common rates for NVH applications:

Rate (Hz)	Bandwidth	Application
12,800	5 kHz	Low-frequency structural vibration
25,600	10 kHz	General vibration analysis
51,200	20 kHz	Full audio bandwidth, acoustic testing
102,400	40 kHz	High-frequency diagnostics

The aggregate sampling rate (rate × channel count) must not exceed the device's maximum throughput. For USB devices, bus bandwidth may further limit the achievable rate. Check NI MAX device specifications for maximum rates.

Recording Workflow

Open Acquisition → NI DAQ and select the target device.
Add channels and configure input type, range, and sensitivity.
Set the sampling rate appropriate for your measurement bandwidth.
Configure the trigger mode (Immediate for manual start).
Click Monitor to verify live signal levels.
Click Record to begin acquisition.
Data is streamed to disk as a V-Listen HDF time-domain file.
Click Stop or wait for the configured duration/sample count.

Troubleshooting

No devices found — Verify NI-DAQmx driver is installed and the device passes self-test in NI MAX.
Overrun errors — Reduce sampling rate or channel count. Ensure the PC has adequate disk write speed (SSD recommended).
Noisy signal — Use differential terminal configuration. Check cable shielding and grounding. Ensure IEPE excitation is enabled for IEPE sensors.
Trigger not firing — Verify trigger level is within the signal range. Increase hysteresis if the signal is noisy near the threshold.