The National Instruments USB-6421 is a high-performance USB Data Acquisition Device, part of the mioDAQ series, designed to meet the demands of complex test and measurement applications. This device features 16 single-ended (or 8 differential) analog input channels, 2 analog output channels capable of providing output voltages from ±10 V at a rate of 250 kS/s/channel, and 16 digital I/O channels. The digital I/O channels support a variety of functions, including triggering and clocking for the four available 32-bit counters, which are capable of pulse width, edge counting, and semi-period measurements. The USB-6421's maximum single-channel sampling rate reaches 250 kS/s, ensuring rapid and precise data collection across multiple channels simultaneously.

Connectivity is facilitated through a USB Type-C interface for bus power, and the device incorporates two 36-position spring terminal connectors that can be secured with screw flanges at a torque of 1.80 lb/in. The USB-6421 is designed for a wide operating temperature range of 0 °C to 55 °C, and can be stored safely at temperatures between -20 °C and 70 °C. The device has compact dimensions of 116.7 mm x 177.0 mm x 30.4 mm (4.59 in. x 6.97 in. x 1.20 in.) and weighs 590 g (1.30 lb), making it highly portable. It is recommended to allow a warm-up period of 15 minutes and to calibrate the device every two years to ensure optimal performance. With published APIs and examples available for LabVIEW, Python, C/C++, and NI's free FlexLogger Lite program, the USB-6421 is an excellent choice for versatile data acquisition applications.