Description
NI PXI-6115 | 4-Channel 10 MS/s Simultaneous PXI Multifunction DAQ
Dynamic Project Introduction
High-speed transient capture, radar signal processing, ultrasonic testing, and multi-channel vibration analysis require data acquisition hardware that can sample multiple inputs at the exact same instant without phase delay. Standard multiplexed DAQ cards cycle through channels sequentially, introducing time skew between inputs that distorts fast signal correlation. The National Instruments PXI-6115 multifunction DAQ module eliminates this limitation by utilizing NI’s S-Series architecture, featuring an independent dedicated ADC for each of its 4 analog input channels.
Engineered to sample at 10 MS/s per channel concurrently, the PXI-6115 ensures zero phase lag between inputs while providing deep onboard sample FIFOs and flexible triggering controls. (Honestly, having true simultaneous sampling across all channels is non-negotiable when you are trying to measure precise time-of-flight or phase relationships in dynamic RF and sensor testing.) Backed by 2 analog outputs, 8 digital I/O lines, and two general-purpose counters, the PXI-6115 delivers robust performance for high-speed test cells—though maintaining absolute measurement fidelity requires proper shielded cabling and clean signal grounding.
PXI-6115
Key Technical Specifications
- Manufacturer & System Platform: National Instruments (NI) / PXI S-Series Simultaneous DAQ
- Module Part Number: PXI-6115 / 778667-01 / 183667F-01
- Analog Input Channels: 4 simultaneously sampled differential channels
- ADC Resolution & Type: 12 bits (Dedicated successive approximation ADC per channel)
- Maximum Sampling Rate: 10 MS/s per channel (simultaneous)
- Analog Input Ranges: Software-selectable ranges from \pm 0.2 V up to \pm 42 V
- Analog Outputs: 2 channels, 12-bit resolution, 4 MS/s update rate, \pm 10 V range
- Digital I/O: 8 TTL/CMOS digital I/O lines
- Counter/Timers: Two 24-bit, 20 MHz general-purpose counter/timers
- Front Panel Connectors: 68-pin high-density SCSI-type connector
- Operating Ambient Temperature: 0°C to +55°C (32°F to 131°F) continuous operational envelope
- Dimensions & Weight: Standard 3U PXI single-slot module, approximately 0.23 kg (0.51 lbs)
Global Sourcing & Live-Test SOP (Transparency Core)
Sourcing secondary-market or surplus high-speed DAQ hardware requires exhaustive signal integrity and frequency validation before introducing units into production test environments. Every NI PXI-6115 module entering our inventory undergoes a strict five-stage bench qualification process:
- Inbound Visual & Connector Inspection: Serial numbers and PCB revision stamps are cross-referenced against NI manufacturing databases. We inspect the 68-pin front SCSI connector for bent or pushed-in pins and check board edge connectors for gold-plating wear.
- Live PXI Rack Simulation: The PXI-6115 module is inserted into an NI PXI-1033 or PXIe-1082 test chassis connected to a development PC running NI-DAQmx and LabVIEW.
- Simultaneous Sampling & Phase Skew Test: Using a multi-channel pulse generator (such as a Keysight 81150A) connected via a shielded 68-pin breakout box, we inject a high-frequency fast-edge step signal simultaneously into all 4 channels. We use automated test scripts to verify that channel-to-channel phase skew is zero and measure ADC linearity and dynamic range at 10 MS/s.
- Output & Counter Validation: Analog output channels are checked for voltage swing stability (\pm 10 V), and counter/timer pins are verified for frequency generation and edge counting.
- Final Prep: Calibration registers are verified against baseline specs, protective connector caps are fitted, and the PXI-6115 module is sealed inside heavy-duty anti-static moisture-barrier packaging.
The Field Engineer’s Pitfall Guide
❗ Exceeding Maximum Input Voltage Limits on High-Speed Channels: Never apply voltages exceeding the maximum rated input range or over-voltage protection thresholds (typically \pm 42 V range limit) directly to the analog inputs. Over-voltage spikes on high-speed S-Series front ends can permanently damage the dedicated ADC input amplifiers.
❗ Using Unshielded Wiring in High-Speed Transient Environments: When acquiring 10 MS/s signals, always use properly shielded twisted-pair cabling (such as NI SH68-68-EIA cables). Running unshielded hookup wires picks up ambient electromagnetic interference (EMI), creating high-frequency noise floors that mask low-level signal details.
❗ Failing to Secure the 68-Pin Front SCSI Cable Thumbscrews: In high-vibration test cells, loose SCSI connector thumbscrews cause micro-vibrations across the 68 pins. This intermittent contact creates erratic open-circuit faults, triggering DAQmx buffer errors and data packet dropouts during high-speed streaming.
Intent-Driven FAQ
Q: What is the main operational advantage of the PXI-6115 over standard multiplexed DAQ cards? The PXI-6115 features a dedicated analog-to-digital converter (ADC) for each of its 4 input channels. This allows all 4 channels to sample simultaneously at 10 MS/s with zero phase delay, whereas multiplexed cards share a single ADC and introduce time skew between channel measurements.
Q: What cable and terminal block do I need to connect field signals to the PXI-6115? Because the PXI-6115 utilizes a 68-pin SCSI front connector, you typically use an NI SH68-68-EIA shielded cable paired with a screw terminal accessory like the NI CB-68LP or SCB-68 to break out signals cleanly.
Q: What software driver is required to control the PXI-6115 in a modern test system? The PXI-6115 is controlled using the NI-DAQmx driver software. It provides full API support for development environments including LabVIEW, LabWindows/CVI, C#, Python, and MATLAB.
Q: Is the PXI-6115 compatible with hybrid PXI Express (PXIe) chassis slots? Yes. Like most 3U S-Series PXI modules, the PXI-6115 is electrically and mechanically forward-compatible with hybrid PXIe chassis slots, ensuring seamless operation in both legacy PXI and modern PXIe test racks.
Q: Can the PXI-6115 stream data continuously to disk at 10 MS/s per channel? Yes, provided your PXI chassis backplane and host controller support high-speed DMA data transfer rates. The PXI-6115 includes deep onboard FIFO buffers and hardware DMA channels to support continuous streaming of high-speed data to host memory.
