USB-6255 80-Channel USB M Series Multifunction DAQ
The NI USB-6255 is a high-density M Series multifunction data acquisition device designed for systems requiring a large number of analog voltage measurements from one USB interface.
It provides 80 single-ended or 40 differential analog inputs with 16-bit resolution. The maximum input rate is 1.25 MS/s on one channel and 750 kS/s aggregate during multichannel scanning.
Two high-speed analog outputs, 24 digital I/O lines and two 32-bit counters support stimulus, fixture control, frequency measurement and encoder applications.
Key Features of the USB-6255
- 80 single-ended or 40 differential analog inputs
- 16-bit analog input resolution
- 1.25 MS/s single-channel sampling
- 750 kS/s aggregate multichannel sampling
- Seven programmable voltage ranges
- 1.7 MHz small-signal input bandwidth
- Two 16-bit analog outputs
- Up to approximately 2.86 MS/s analog output
- 24 individually programmable digital I/O lines
- Two 32-bit counters
- USB 2.0 Hi-Speed communication
- Screw-terminal, mass-termination and OEM versions
- NI-DAQmx software support
USB-6255 Technical Specifications
| Product Model | USB-6255 |
|---|---|
| Analog Inputs | 80 single-ended or 40 differential |
| ADC Resolution | 16 bits |
| Single-Channel AI Rate | 1.25 MS/s maximum |
| Multichannel AI Rate | 750 kS/s aggregate |
| Input Ranges | ±0.1 V, ±0.2 V, ±0.5 V, ±1 V, ±2 V, ±5 V and ±10 V |
| Input Bandwidth | 1.7 MHz |
| CMRR | 100 dB from DC to 60 Hz |
| Analog Outputs | 2 |
| DAC Resolution | 16 bits |
| Output Range | ±10 V |
| Digital I/O | 24 individually programmable lines |
| Counters | 2 × 32-bit |
| USB Interface | USB 2.0 Hi-Speed |
| External Power | Required |
| Connector Options | Screw terminal, mass termination and OEM |
USB-6255 Part Number and Accessories
USB-6255 configurations differ by connector and enclosure. High-channel-count installations should be planned around the selected terminal and cable arrangement before the device is ordered.
| Configuration or Accessory | Description |
|---|---|
| USB-6255 Screw Terminal | Integrated field wiring for high-channel-count measurements |
| USB-6255 Mass Termination | High-density connection to custom test fixtures |
| USB-6255 OEM | Board-level integration into custom equipment |
| Shielded 68-Pin Cables | Connections between mass-termination ports and terminal accessories |
| SCB-68A | Shielded screw-terminal block for compatible 68-pin connections |
| External Power Supply | Required DC power for enclosed versions |
80-Channel Analog Input Architecture
The USB-6255 is optimized for channel density. Up to 80 single-ended signals can be measured, making it useful for large fixtures, research experiments and environmental monitoring systems.
When differential wiring is used, the available count is 40 channels. Differential measurements provide improved rejection of voltage shared by both signal conductors.
Aggregate Sampling Considerations
The 1.25 MS/s specification applies to one active channel. Multichannel acquisition is limited to 750 kS/s aggregate, which must be divided among the scanned channels.
If all 80 channels are sampled evenly, the theoretical average rate per channel is substantially lower than 750 kS/s. Measurement software should be configured according to the required rate for each signal.
Source Impedance and Settling
The analog inputs are multiplexed. High source impedance can prevent the input amplifier from settling after switching between channels, especially when adjacent signals have large voltage differences.
Buffer high-impedance sensors, increase conversion time or rearrange the scan list when settling error affects measurement accuracy.
USB-6255 Applications
- High-channel-count data logging
- Environmental chamber monitoring
- Production test fixtures
- Battery and power-system monitoring
- Research experiments
- Industrial process monitoring
- Electronic assembly validation
- Temperature and pressure system monitoring
- Large sensor arrays
Environmental Test Systems
The USB-6255 can acquire voltage outputs from many temperature, humidity, pressure and process sensors. Appropriate conditioning is required for sensors that do not produce directly compatible voltage signals.
Production Test Fixtures
A single USB-6255 can connect many DUT test points to one acquisition system. Digital lines and analog outputs can control compatible fixture functions and stimulus signals.
USB-6255 Installation Workflow
Step 1: Determine the Required Terminal Mode
Calculate the single-ended or differential channel count and plan every signal reference.
Step 2: Select the Connector Configuration
Choose integrated screw terminals or mass termination based on fixture construction and maintenance requirements.
Step 3: Install NI-DAQmx
Install compatible driver software before connecting and testing the device.
Step 4: Connect External Power and USB
Apply the approved external supply and connect the USB interface directly to the host computer.
Step 5: Validate the Wiring in Groups
Test small channel groups before connecting the complete 80-channel system. This makes wiring errors easier to identify.
Step 6: Test the Full Scan List
Check the aggregate rate, channel settling, scaling, data transfer and storage performance.
USB-6255 Troubleshooting
Some Channels Show Incorrect Voltages
Verify terminal assignments and input mode. Differential and single-ended configurations use different channel pairings.
Measurements Change When More Channels Are Added
Adding channels changes the scan sequence and per-channel timing. Review aggregate rate, source impedance and settling requirements.
Adjacent Channels Interfere with Each Other
Use shorter shielded cables, reduce source impedance and rearrange high-amplitude and low-amplitude signals within the scan list.
The Device Cannot Sustain the Requested Rate
Confirm that the requested rate is below the 750 kS/s aggregate multichannel limit and that the USB host can service the acquisition buffer.
USB-6255 Comparison
| Model | Analog Inputs | Analog Outputs | Digital I/O | Primary Advantage |
|---|---|---|---|---|
| USB-6251 | 16 | 2 | 24 | Compact high-speed acquisition |
| USB-6255 | 80 | 2 | 24 | Maximum analog input density |
| USB-6259 | 32 | 4 | 48 | Balanced high-density multifunction I/O |
Select the USB-6255 when analog input density is the principal requirement. Select the USB-6259 when additional analog outputs and digital I/O are more important.
USB-6255 Frequently Asked Questions
How many analog inputs does the USB-6255 provide?
It provides 80 single-ended or 40 differential analog inputs.
What is the maximum multichannel sampling rate?
The maximum aggregate multichannel rate is 750 kS/s.
Does it provide analog outputs?
Yes. The USB-6255 includes two 16-bit analog output channels.
Is it a simultaneous-sampling device?
No. It uses a multiplexed ADC architecture.
Does it require external power?
Yes. Enclosed USB-6255 versions require an appropriate external DC supply.
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