© National Instruments Corporation 15 NI USB-9421 User Guide and Specifications
Bus Interface
USB specification.................................. USB 2.0 Hi-Speed
Physical Characteristics
Dimensions
With screw terminal........................14.0 cm × 8.8 cm × 2.5 cm
(5.52 in. × 3.47 in. × 1.00 in.)
With 25-pin D-SUB........................12.6 cm × 8.8 cm × 2.5 cm
(4.95 in. × 3.47 in. × 1.00 in.)
Screw-terminal wiring............................12 to 24 AWG copper conductor
wire with 10 mm (0.39 in.) of
insulation stripped from the end
Torque for screw terminals.................... 0.5 – 0.6 N · m (4.4 – 5.3 lb · in.)
Weight
With screw terminal........................Approx. 250 g (8.8 oz)
With D-SUB................................... Approx. 245 g (8.6 oz)
Safety
If you need to clean the module, wipe it with a dry towel.
Safety Voltages

NI USB-9421 with Screw Terminal SafetyVoltages

Connect only voltages that are within these limits.
Channel-to-COM................................... 30 V max
Isolation
Channel-to-channel.........................No isolation between channels
Channel-to-earth ground
Withstand.................................2,300 Vrms, verified by a 5 second
dielectric withstand test
Continuous...............................250 Vrms,
MeasurementC ategory II
Measurement Category II is for measurements performed on circuits
directly connected to the electrical distribution system. This category refers
to local-level electrical distribution, such as that provided by a standard
wall outlet (for example, 115 V for U.S. or 230 V for Europe).