Main Page : DAQ Multifunction I/O Accessory Guide


Use this guide to better understand specifications, differences, and answer common questions about using your NI DAQ terminal block or connector block accessories as signal breakouts. This guide will discuss through NI naming terminology, wiring considerations, signal mapping and pinouts, choosing the right accessory to meet your needs—from low cost to high performance noise reducing, shielded, and more.


Using the DAQ Cable and Accessory Guides

This guide is intended to cover accessories designed for use with NI DAQ devices, and their use cases. It does not cover use with other NI product families such as Digital Instruments (formerly HSDIO), C Series, or Reconfigurable I/O (formerly known as R Series), although some may use similar or the same accessories. It also does not cover legacy or End of Life (EOL) NI DAQ accessories.

If you seek information about a specific connector block or terminal block, NI recommends that you first review this page and its more general information to better understand the product offerings, and then jump to the page for your specific model.


Understanding NI Accessory Terminology

NI accessories come in a variety of shapes, orientations, features, and functionality. This section briefly explains what some of that terminology means. If you want to learn more about a specific accessory, visit the DAQ Accessory Guide Page for your accessory, or its product page.

Anatomy of a Model Name

Use this section to better understand your NI accessory's model name and numbering.

Model Prefixes

    • Shielded Connector Block (SCB) - These accessories feature screw terminal connectivity inside of a shielded enclosure providing rugged, very low-noise signal termination. Example: SCB-68A
    • Connector Block (CB) - CB unshielded screw connector blocks are low-cost accessories. These connector blocks feature standoff feet for use on a desktop or mounted in a custom breakout panel. Example: CB-68LP
    • Terminal Block (TB) - TB accessories connect directly to the front of your PXI or PXIe DAQ module without the need for a cable. These space-saving accessories feature shielded screw terminal or SMB connectivity providing rugged, very low-noise signal termination. Example: TB-2705
    • Terminal Block (TBX) - TBX unshielded screw terminal blocks are low-cost accessories that include hardware for mounting on a standard DIN rail. Example: TBX-68 
    • BNC - NI BNC accessories feature some connectors with BNC connectivity, typically for analog differential or single-ended connections. They also feature screw terminal connections for digital and counter connections. Example: BNC-2120
    • Connector Accessory (CA) - This user configurable signal conditioning enclosure is designed for maximum user-defined I/O connectivity and flexibility. Example: CA-1000

Connector Pin Counts

Most SCB, CB, and TBX accessories typically follow the model prefix with a dash and a number indicating the number of pins on its connectors. Common DAQ connectors are -37, -68, and -100 for 37-pin, 68-pin and 100-pin connectors, respectively. Note that some connectors with the same pin count may come in different forms, such as the 68-pin VHDCI or SCSI.


Following the connector pin count, some accessories also include a suffix indicating additional information or functionality. Some of the more common used are:

    • LP - This accessory features a vertical-mounted connector. Example: CB-68LP
    • LPR - This accessory features a right-angle-mounted connector. Example: CB-68LPR
    • FV - This accessory features a vertical-mounted connector and mounts perpendicular or vertical to the DIN rail. Example CB-37FV
    • FH - This accessory features a vertical-mounted connector and mounts in line or horizontal with the DIN rail. Example: CB-37FH
    • F-HVD - This accessory features a higher category voltage rating, and the ability to DIN-rail mount. Example: CB-37F-HVD


General Accessories Glossary

Connector Block versus Terminal Block

These terms are used interchangeably in the context of NI DAQ accessories. These accessories act as a breakout box from the pins on your NI DAQ device, featuring screw terminals or BNC connectivity when wiring signals to your system.

Shielded vs Unshielded

    • Shielded - NI shielded accessories feature rugged, very low-noise signal termination. Note that NI DAQ products typically must be operated with shielded cables and accessories to ensure compliance with Electromagnetic Compatibility (EMC) requirements. Example: SCB-68A
    • Unshielded - NI unshielded accessories offer low-cost alternatives. They do not provide EMC shielding and thus, are more susceptible to noise interference.  If unshielded cables or accessories are used, the EMC specifications for the device or module are no longer guaranteed. Example: CB-68LP


    • Screw Terminal - A screw terminal is a type of electrical connector where a wire is held by the tightening of a screw. NI recommends one wire per screw terminal, and thus differential signals will require two screw terminals. Example: SCB-68A
    • Bayonet Neill–Concelman (BNC) - Simply known in industry by its acronym, BNC is a quick connect/disconnect for coaxial cables to assist in noise reduction. In this configuration, a signal is carried down the spline (or pin) of the BNC cable, and the COM(AI-), GND or SENSE is carried down the shielding of the BNC cable. Example: BNC-2120
    • SubMiniature Version B (SMB) - Similar to the coaxial cable functionality to BNC, but feature a smaller size and latching mechanism. Example: TB-2708
    • Deutsches Institut für Normung (DIN) Rail Mount - Simply known by its acronym, a DIN rail is an industry-standard metal rail used to mount equipment, typically inside of equipment racks. NI accessories featuring DIN rail mounts include or make available for purchase the hardware required for a simple mounting procedure. Example: TBX-68
    • High Voltage Terminal Block - Industry standard electrical measurement categories or classifications (CAT I, CAT II, and so on) define the total continuous energy that can be safely used at a single point in a circuit by both the working voltage and an impulse or transient overvoltage. Most NI DAQ accessories only support lower level voltages, defined in their specifications. However, some accessories, such as the CB-37F-HVD support higher measurement categories, such as CAT II (150V). Example: CB-37F-HVD

Common Cable Connector Types Found on NI Accessories

For more information on replacement connectors for your NI DAQ accessory, use the information found throughout this guide, as well as NI DAQ Device Custom Cables, Replacement Connectors, and Screws.

  • D-Sub (37-pin) - Industry standard 37‑pin D-Sub (DSUB) connector. Click here for an example.
  • SCSI 0.050 D-Type (68-pin and 100-pin) - Industry standard SCSI connector standard featuring 0.050 in pin spacing. Commonly found on many NI DAQ accessories, these accessories are compatible with older DAQ devices and modules with SCSI connectors as well as newer DAQ devices and modules with VHDCI connectors. Reference compatibility information found in this series of pages for which cable to use with your device or module. Click here for a 68-pin example.
  • VHDCI .8mm (68-pin) - An improvement on the SCSI connector allowing a smaller footprint with 0.8 mm pin spacing, and fewer bent pins during connection. This connector is primarily used on PXI mounted terminal blocks to connect to modules with VHDCI connectors. Click here for an example.



Signal to Pin Mapping When Wiring Up an Accessory

When wiring your sensor or other signals into your NI accessory it is important to understand which screw terminal or BNC connectors map back to which terminals or pin numbers on your NI DAQ device. For accessories not covered in the extended information pages from this guide, this guidance generally applies to mapping any NI device's lines to the accessory.

If your device has extended information available in this guide, there may also be additional information on its DAQ Accessory Guide page.

First, it is important to understand that each device may use its own pinout or pin mapping scheme. Some families of devices with the same pin count will use the same numbering and signal combinations, but others may not. There are several resources you can use to find this scheme.

  • Quick Reference Pinout Labels - If available, this is the easiest and quickest way to find your signal mapping. NI recommends that you print out and attach the quick reference label to your accessory.
  • User Manuals and User Guides - You can find your model's pinout in its user manual or user guide. Search NI Manuals to find your model's user manual or user guide.
  • NI-DAQmx Help - The NI-DAQmx Device Terminals Help section contains the pinouts for every hardware model supported by that version of the driver. The NI-DAQmx Help installs locally with your driver, and is also available online.
  • Measurement & Automation Explorer (MAX) - NI MAX is used to configure your NI DAQ hardware, and also references out to many different types of reference information, including device pinouts.
    • Right-click your device name under Devices and Interfaces, and select Device Pinouts to directly navigate to the NI-DAQmx Device Terminals Help topic for your device.
    • Right-click the device name under Devices and Interfaces, and select Help»Online Device Documentation. A browser window opens to with the results of a search for relevant model documentation.
  • All accessories, with the exception of PXI front mounted blocks, connect to a device or module through a cable. Unless you are creating a custom breakout box or test fixture, it's typically unnecessary to understand the pin mapping at each cable and device connector. Instead, you can take the above information in regards to the signal mapping, and use that to wire to the labeled numerical screw or BNC terminals once you have connected your cable.  If you'd still like to review connector pinout or mapping for NI DAQ cables, check out the NI DAQ Cables Guide.


SCB-68A to PCIe/PXIe-6361 Pinout Mapping Example

Warning: Always refer to the product documentation for your specific device. Your device may use a completely different pin mapping than what is used in this example.

Navigate to the PCIe/PXI-6361 entry in the NI-DAQmx Device Terminals Help using one of the methods described above to find the following pinout diagram.

In this example, we want to connect our differential signal, AI 0. Since our differential signal requires two wires for signal and COM, we will use the differential signal names designated in parentheses. In this case, pin 68 of the PCIe/PXIe-6361, denoted by AI 0 (AI 0+), will be our signal connection; the COM will connect to AI 8 (AI 0-) at pin 34.

NI DAQ PCIe-6361 PXIe-6361 Partial Pinout Pins 68 and 34

Figure 1: PCIe/PXIe-6361 Pinout with Pin 68 (AI 0+) and Pin 34 (AI 0-) Highlighted

On the SCB-68A we find terminal 68, to which we can wire our AI 0+ signal wire to, and secure through the screw terminal. Similarly, we find terminal 34 to which we can wire our AI 0- signal.

SCB-68A Screw Terminal Breakout Pins 68 and 34

Figure 2: SCB-68A with Terminals 68 and 34 Highlighted



NI DAQ Accessories Connectivity and Features

The following table lists the most popular NI DAQ accessories, and provides links to their Accessory Guide Page, if available. General compatibility with NI DAQ devices, modules, and cables are listed on each Accessory Guide page, but a more extensive list can be found in the Multifunction DAQ I/O Compatibility guide. For more information about an accessory not covered in this guide, review the accessory's manual.

Use this table to quickly identify NI DAQ accessory connectivity, mounting, and features.
ConnectivityShieldingProduct PageAccessory GuideMountingAdditional Features
Screw TerminalShielded for high performance noise reductionSCB-68A1SCB-68ADIN Rail2See guide
SCB-68SCB-68-See guide
SCB-100ASCB-100ADIN Rail2See guide
SCB-100SCB-100-See guide
TB-2705-PXI ModulePXI Mounted
TB-2706-PXI/PXIe ModulePXI Mounted
TB-2621-PXI/PXIe ModulePXI Mounted, High Voltage
Screw TerminalUnshielded for low cost applicationsCB-68LP-Custom Panel-
CB-68LPR-Custom Panel-
TBX-68-DIN Rail-
CB-37F-LP-Front mount on module-
CB-37FV-DIN Rail-
CB-37FH-DIN Rail-
CB-37F-HVD-DIN RailHigh voltage
BNCShielded for high performance noise reductionBNC-2110-DIN Rail2Differential AI
BNC-2111-DIN Rail2Single-Ended  AI
BNC-2115-DIN Rail2AI Extended I/O
BNC-2120-DIN Rail2-
SMBShielded for high performance noise reductionTB-2708-PXI Module-
TB-2709-PXI Module-
Custom ConnectivityShielded signal conditioning enclosure designed for maximum user-defined I/O connectivity and flexibilityCA-1000-Rack2User configurable signal conditioning

1SCB‑68A and BNC‑2090A are newer designs recommended for all new applications over the SCB‑68 and BNC‑2090.
2DIN rail or rack mount kit sold separately.

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