National Instruments 781424-01 CompactDAQ Chassis

The National Instruments 781424-01 is an Ethernet CompactDAQ chassis made for small, dispersed sensor measurement applications. It is also known as the cDAQ-9188. This chassis manages the timing, synchronization, and data transfer between C Series I/O modules and an external host. It uses a variety of C Series modules to support a combination of digital and analog I/O as well as counter/timer metrics. Applications involving quadrature encoders, PWM, event counting, pulse train creation, and period or frequency measurement can benefit from the chassis' four 32-bit general-purpose counters/timers, which are accessed by a hardware-timed digital C Series module.

For analog input, the chassis has an input FIFO size of 127 samples per slot and a timing accuracy of 50 ppm of the sample rate, with a timing resolution of 12.5 ns. The installed C Series modules define the maximum sampling rate and number of channels. Analog output capabilities include hardware-timed tasks with onboard regeneration supporting 16 channels and a maximum update rate of 1.6 MS/s (multi-channel, aggregate). The particular C Series modules utilized determine which tasks are hardware-timed and which are not recycled. The analog output's timing precision and resolution, at 50 ppm accuracy and 12.5 ns resolution, are identical to those of the input.

Digital triggers in the 781424-01 can be sourced from any chassis or module PFI terminal with software-selectable polarity for most signals. Analog input functions include start, reference, pause triggers, sample clock, and sample clock timebase. Analog output functions consist of start and pause triggers, sample clock, and sample clock timebase. Counter/timer functions available are gate, source, HW_Arm, Aux, A, B, Z, and Up_Down.

Network connectivity is robust with support for TCP/IP and UDP protocols. The 781424-01 chassis uses multiple network ports for configuration and data streams, including HTTP, TCP, and UDP. It supports DHCP, static, and link-local IP configurations, with a default MTU size of 1500 bytes and jumbo frame support up to 9000 bytes. The Ethernet interface supports communication rates of 10/100/1000 Mbps, with a maximum cabling distance of 100 meters per segment.