ADLINK USB-2405 Dynamic Signal Acquisition Module Deployment Guide

ADLINK USB-2405 24 bit Dynamic Signal Acquisition Module Application and Debugging Manual

In the fields of vibration analysis, acoustic measurement, structural health monitoring, and rotating machinery fault diagnosis, high-resolution and low-noise dynamic signal acquisition modules are the core front-end for obtaining real physical quantities. ADLINK USB-2405 is a 24 bit ∑ - Δ dynamic signal acquisition module powered by USB 2.0 bus, providing 4 synchronous sampling analog inputs, with a maximum sampling rate of 128 kS/s per channel, and built-in IEPE excitation source (2mA constant current), which can be directly connected to accelerometers and microphones. Its flexible triggering mode, programmable functional I/O, and complete self calibration capability make it an ideal choice for portable testing systems. This article systematically outlines the engineering application points of this module from hardware characteristics, signal conditioning, trigger configuration, software deployment to typical fault handling.

Product positioning and core advantages

USB-2405 is designed specifically for dynamic signal measurement that requires high dynamic range and low distortion, mainly targeting:

Vibration monitoring and order tracking of rotating machinery;

Environmental noise and sound quality analysis;

Structural modal testing (impact response);

Automotive NVH (Noise, Vibration, and Smoothness) test.

Its core advantages include:

4-channel synchronous sampling: no phase delay between channels, ensuring multi-channel signal correlation;

24 bit resolution: dynamic range up to 100dB (@ 1kHz, -60dBFS input), effectively capturing weak signals;

Built in anti aliasing filter: combining digital filters with analog RC filters to suppress out of band noise;

IEPE incentive source: Each channel has an independent 2mA constant current source, supports AC coupling, and is suitable for piezoelectric sensors;

Bus power supply: only required 400mA@5V No need for external power supply, excellent portability;

Multi functional bracket: supports desktop, DIN rail, and wall mounted installation, suitable for on-site layout.

Electrical specifications and precision indicators

2.1 Analog Input

Number of channels: 4 differential/pseudo differential (software configuration);

ADC type: 24 bit ∑ - Δ, built-in digital filter;

Input range: ± 10V (fixed), data format is binary complement code;

Input impedance: 200k Ω between positive and negative input terminals, 16.93k Ω between negative input terminal and ground;

Coupling method: AC or DC, software optional (AC cut-off frequency -3dB about 0.4Hz);

Sampling rate: High resolution mode (1k~52.734kHz) or high-speed mode (52.734kHz~128kHz), finely adjusted through DDS, with a resolution of 0.0003Hz;

FIFO: 8k sampling points (shared by all channels).

2.2 DC accuracy (typical at 25 ℃)

Offset error: ± 0.15mV (typical), ± 0.3mV (maximum);

Gain error: ± 0.15% (typical), ± 0.3% (maximum).

2.3 Dynamic performance (typical values)

THD+N (1kHz, 8.9Vpk differential input): -91dB;

CMRR（20Hz~1kHz）：60dB；

Crosstalk (1kHz): -102dB;

System noise (high-resolution mode): 50 μ Vrms;

Bandwidth: Approximately 0.49 x sampling rate at -3dB (e.g. bandwidth of approximately 25kHz at 51.2kS/s);

Passband flatness (20Hz~20kHz): ± 0.01dB.

2.4 Programmable Functional I/O (GPIO)

Two channels of 3.3V/TTL compatible single ended I/O;

Can be configured as static digital input/output, frequency counter (maximum 4MHz), PWM output (maximum 4MHz), digital trigger input, synchronous sampling clock input (maximum 128kHz);

Overvoltage protection: -2V~+7V.

Hardware installation and device identification

3.1 Unpacking and Connection

The package includes: USB-2405 module, multifunctional bracket, 2-meter USB cable, DIN rail installation kit, quick guide, and software CD.

Before first use, the driver (UD-DASK 1.2.2.0627 or above or DAQPilot 2.6.1.0628 or above) must be installed before connecting the USB cable. After the module is powered on, the firmware loads for about 6 seconds, and the LED indicator light changes from amber to green, indicating readiness. If the LED does not turn green, it may indicate insufficient power supply to the USB port (requiring 400mA). It is recommended to use a USB hub with built-in power supply or a rear port on the motherboard.

3.2 Device ID Setting

There is a rotary switch (0-7) on the back of the module for setting the device ID. When multiple modules of the same model are connected to the same PC, different IDs must be set, otherwise the drivers cannot be distinguished. The ID value is read during driver initialization and can be obtained through the API.

3.3 Installation method

The multifunctional bracket supports three types of fixation:

Desktop: Module card in bracket, providing cable management space at the bottom;

DIN rail: With the matching rail buckle, it can be quickly installed in the control cabinet;

Wall mounted: There are 4 mounting holes with a diameter of 3.4mm on the back of the bracket, which are fixed with flat head screws.

Detailed explanation of analog input signal conditioning

4.1 Front end configuration (see Figure 3-2)

Differential/pseudo differential selection: Differential mode is suitable for grounded reference signal sources and can suppress common mode noise; The pseudo differential mode is suitable for floating signal sources (such as uninsulated sensors), where the negative input terminal is connected to the local ground through a 20k Ω resistor to provide a reference potential.

Coupling method: DC coupling preserves the DC component in the signal, suitable for pressure sensors or slowly changing signals; AC coupling filters out DC bias through a high pass RC network (-3dB @ 0.4Hz), suitable for AC dynamic signals (such as vibration acceleration).

IEPE incentive: After enabling, each channel outputs a constant current of 2mA to the BNC center conductor and automatically switches to AC coupling. The voltage signal returned by the sensor is superimposed on the excitation voltage and sent to the ADC through a DC blocking capacitor. Note that IEPE mode is only used for piezoelectric sensors with built-in amplifiers and cannot be used for ordinary voltage sources.

4.2 Data Format and Range

The input range is fixed at ± 10V, 24 bit data is represented by binary complement, and the least significant bit (LSB) is 1.19 μ V. The numeric code 0x000000 corresponds to 0V, 0x7FFFFF corresponds to+9.99999881V, and 0x800000 corresponds to -10V. After reading the original code, the software needs to convert it into a voltage value.

4.3 Sampling rate and anti aliasing

The sampling clock is generated by DDS and can be adjusted in 0.0003Hz steps within 1kHz~128kHz. Two working modes are automatically switched by sampling rate:

High resolution mode (≤ 52.734kHz): The digital filter extraction ratio is 512, providing better in band noise performance;

High speed mode (>52.734kHz): Extract ratio of 256, expands bandwidth but slightly increases noise floor.

The internal digital filter is a multi-stage FIR with an out of band attenuation of 100dB, combined with an RC low-pass (about 500kHz cutoff) at the input to jointly suppress aliasing. The frequency response curve shows that the flatness is better than ± 0.15dB within 0.49 times the sampling rate, and it quickly rolls off after exceeding this frequency.

Trigger mechanism and collection mode

USB-2405 provides rich trigger sources and modes to adapt to different transient or continuous acquisition requirements.

5.1 Trigger Source

Software trigger: Immediately start collecting after calling the API, with no external signals.

External simulation trigger: Choose one of the four input channels as the trigger source and set the high/low level threshold (24 bit resolution). The triggering condition can be "Below Low" or "Above High".

External digital trigger: TTL level input through GPIO pin, programmable to have effective rising or falling edge, with a minimum pulse width of 20ns.

5.2 Trigger Mode (Key)

Post Trigger: Collect a specified amount of data after triggering (without pre triggering).

Pre Trigger: Continuously store data from the start of collection until the triggering event arrives, retaining the first N samples before triggering, and may continue collection thereafter (depending on the mode). If the number of collected samples is less than N when the trigger arrives, ignore the trigger until the condition is met.

Delay Trigger: After triggering, wait for the specified delay count (32 bits, maximum 2 Ω² -1) before starting data collection.

Middle Trigger: Simultaneously collect M samples before and N samples after triggering (M+N ≤ 8k), suitable for recording the complete waveform before and after the event.

Gated Trigger: Data is only collected during periods when the trigger signal is at a high (or low) level, and pauses when the level is reversed.

Re Trigger: In post trigger or delayed trigger mode, multiple triggers can be set, with a fixed number of points collected after each trigger and repeated until the specified number of times.

Important limitation: In pre trigger and mid trigger modes, the buffer size is fixed at 8k sampling points (total of all channels), so M+N must be ≤ 8192. Special attention should be paid when designing the collection length.

Programmable functional I/O applications

GPIO can be configured through software to the following modes (only one can be selected at a time):

Static digital I/O: Read and write high and low levels through APIs, used to control external indicator lights or read switch status.

Frequency/Event Counter: measures the frequency of the input signal (up to 4MHz), an internal 32-bit counter that can count the number of pulses within a specified time.

PWM output: By setting the initial count value and pulse width count value, a square wave with variable frequency and duty cycle is generated, with a maximum frequency of 4MHz.

Digital trigger input: As an external digital trigger source for continuous analog acquisition (see previous section).

Synchronous sampling clock input: The continuous clock signal (1k-128kHz) input from the external can drive ADC sampling, achieving multi module synchronization. Note that multiple USB-2405 must share the same external clock and trigger to ensure phase consistency between channels.

Calibration and precision maintenance

7.1 Calibration Architecture

The module integrates a precise reference voltage source and TrimDAC (digital to analog adjustment) internally, and is calibrated and stored with constants in the factory area of EEPROM (read-only) at the factory. The user area can store subsequent self calibration results.

7.2 Self calibration process

Preheat the module for at least 15 minutes to ensure stable temperature;

Run the calibration tool provided by ADLINK or call the API (without the need for any external signals);

Software automatically measures internal reference, calculates offset and gain errors, and updates TrimDAC values;

The new constant can be saved to the EEPROM user area for retention after power failure.

Self calibration can compensate for errors caused by environmental temperature changes and time drift. It is recommended to perform it once a year or after significant environmental changes. If you need to restore the factory values, you can copy the factory zone constants to the user zone through software.

Software Support and Development Tools

UD-DASK: a low-level driver library that supports languages such as C/C++, VB, C #, etc., providing a complete API for configuring sampling, triggering, GPIO, and data reading.

DAQPilot: A task oriented SDK that supports advanced environments such as LabVIEW and MATLAB, simplifying programming.

U-Test: A free practical tool that enables data acquisition, waveform display, FFT analysis, and digital I/O control without programming. It is suitable for quickly verifying system connections and signal quality.

Common troubleshooting and solutions

Fault 1: LED does not light up or remains red after inserting USB

Check if the USB cable is intact and replace the cable for testing;

Try different USB ports (prioritize USB 2.0 port on the motherboard rear);

If using a USB hub, ensure that its power supply capacity is ≥ 500mA;

Check if 'unknown device' appears in the device manager, and if so, manually install the driver.

Fault 2: U-Test or user program cannot find module

Confirm that the driver version is correct (UD-DASK ≥ 1.2.2.0627);

Check if the Device ID on the back of the module conflicts with other modules (if there is only one, keep it at 0);

Re plug and unplug the USB, observe the LED changes, and restart the software.

Fault 3: There is a large amount of bias or noise in the collected data

Check the input coupling method: If measuring low-frequency signals but mistakenly setting them as AC coupling, it will cause low-frequency attenuation;

Confirm if IEPE is enabled correctly: IEPE should not be turned on for ordinary voltage sources, otherwise the excitation current will cause a voltage drop across the internal resistance of the source, resulting in offset;

Perform self calibration and update gain/offset constants;

Check if the signal source is grounded together with the tested equipment to avoid ground loops (differential mode can be used).

Fault 4: Trigger unresponsive or incomplete data collection

Verify whether the amplitude of the trigger source signal is within the valid range (the simulated trigger threshold needs to be within ± 10V);

The digital trigger signal level should be compatible with 3.3V/5V TTL and have a pulse width of ≥ 20ns;

In pre trigger mode, ensure that the data buffer is filled with enough samples (≥ number of pre trigger points) after starting the collection, otherwise the trigger will be ignored;

Check if the number of triggers is set correctly and if the buffer is sufficient to accommodate all trigger data.

Fault 5: Phase deviation during multi module synchronization

Confirm that all modules use the same external sampling clock (input through GPIO) and the clock source is low jitter;

Activate all modules simultaneously using the same trigger signal (digital or analog);

Please note that the firmware versions of different modules are consistent, and it is recommended to update to the latest version.

Maintenance and usage suggestions

The working temperature of the module is 0-55 ℃, avoiding direct sunlight and strong convection;

BNC connectors should be regularly inspected to ensure that the contacts are not oxidized;

When not in use for a long time, please disconnect the USB cable and store it in a dry environment;

If it is necessary to replace the battery (onboard RTC battery), the same model must be used and environmentally friendly disposal must be followed.

Technical Support Information

If you are unable to resolve the issue on your own, please contact ADLINK technical support（ service@adlinktech.com ）Provide:

Module model (USB-2405) and serial number;

Operating system version (32/64 bit);

Driver and U-Test versions;

Fault reproduction steps and phenomenon description (including LED status);

Whether to test on multiple PCs.