Product Overview
The National Instruments PCIe-6321 is a multifunction data acquisition card for PCI Express computers. It belongs to the NI X Series family and provides 16 analog input channels, 2 analog output channels, 24 digital input and output lines, and 4 counters. The card is designed for automated test, laboratory measurement, production verification, and machine control applications that need a flexible mix of signal types.
Because the card installs directly in a PCI Express slot, it provides a high bandwidth path to the host computer without external cabling. This makes it suitable for systems that stream continuous data, generate waveforms, or combine fast acquisition with real time decision making. The card is programmed with NI-DAQmx software, which provides a consistent interface across NI data acquisition hardware.
Analog Input
The PCIe-6321 offers 16 analog input channels with 16 bit resolution and a maximum single channel sampling rate of 250 kS/s, with the aggregate rate shared among active channels. Selectable input ranges, including plus or minus 10 V, plus or minus 5 V, and plus or minus 1 V, allow the card to be matched to different sensor and signal levels.
Hardware timed acquisition, external sample clocks, and analog and digital triggering support repeatable measurement sequences. Multichannel scanning can be configured for single ended or differential connections depending on the accessory and wiring. Differential wiring is often preferred for low level signals and for rejecting common mode noise in industrial environments.
Analog Output and Digital I/O
The card includes two 16 bit analog output channels for generating control voltages, setpoints, and waveforms. Hardware timed output allows the card to produce deterministic waveform sequences, which is useful for stimulus response testing, actuator command profiles, and calibration signals. Engineers should confirm the load and settling requirements of the driven device.
Twenty four digital lines provide logic level control, relay driving through external conditioning, and status monitoring. Four 32 bit counters support event counting, frequency measurement, pulse generation, and encoder position tracking. Because digital, counter, and analog operations can share timing resources, the card can coordinate complex mixed signal sequences within one application.
Timing and Synchronization
NI-DAQmx exposes start triggers, reference triggers, pause triggers, and sample clock configuration for the PCIe-6321. These features allow acquisition and generation to be aligned with external events or with other DAQ devices. Counter outputs can be routed to trigger analog operations, and analog events can gate digital tasks.
For larger systems, multiple cards can be synchronized using shared timing and trigger signals where supported. This allows channel counts to be expanded beyond the capacity of one card. Documenting the trigger routing and clock source is important for reproducibility, especially when the system is replicated on multiple test stations.
Software and Integration
The PCIe-6321 is supported by NI-DAQmx and can be programmed with LabVIEW, LabWindows/CVI, Measurement Studio, and other NI-DAQmx compatible environments. The driver provides channel configuration, scaling, calibration, and task management. Signal conditioning accessories and shielded cables are available to connect sensors and signals to the card's connectors.
The card is typically used with screw terminal, spring terminal, or mass termination accessories depending on the number of signals and the wiring style required. Proper shielding, grounding, and separation from power wiring help maintain measurement quality. The card should be installed in a slot that provides adequate airflow and must operate within the host computer's environmental limits.
Typical Applications
Automated test systems with mixed analog and digital I/O
Sensor measurement and voltage monitoring
Control voltage and waveform generation
Encoder position and frequency measurement
Laboratory data acquisition and prototype validation
Production test stations built on PCI Express computers
The PCIe-6321 combines 16 analog inputs, 2 analog outputs, 24 digital I/O lines, and 4 counters on a PCI Express card. Its X Series performance and NI-DAQmx support make it a practical choice for multifunction measurement and control applications.
