NI USB-485/4 4-Port Serial Instrument Control Interface for USB

The NI USB-485/4 is a 4-port RS-485 serial interface that connects multiple instruments and sensors to a computer via USB. Each port features independent DB9 connectors and onboard switchable termination resistors to ensure signal integrity in multipoint configurations. The device supports data rates up to 3 Mbps with user-configurable transmit and receive FIFO buffers, automatic data direction control, and wide common-mode voltage tolerance to accommodate ground potential differences across distributed systems.

Technical Specifications

• Number of Ports: 4


• Serial Standard: RS-485


• Maximum Data Rate: 3 Mbps


• Automatic Data Direction Control: Supported


• Onboard Termination: Switchable 120 Ohm resistors per port


• FIFO Buffers: User-configurable transmit and receive USB Interface


• Connector: 1 × USB Type-A


• Standard: USB 2.0 High-Speed (480 Mbps)


• Power: Bus-powered Electrical & Environmental


• Operating Temperature: −20 °C to 70 °C


• Storage Temperature: −40 °C to 85 °C


• Humidity: 5% to 95% non-condensing


• RS-485 Noise Immunity: Meets RS-485 input voltage tolerance standards Physical


• Serial Connectors: 4 × DB9 male


• Enclosure: Metal or solid plastic construction

Key Features

• Automatic RS-485 data direction control eliminates external signal management


• Multipoint communication capability for distributed sensor networks and daisy-chained instruments


• Wide common-mode voltage range compensates for ground potential differences in industrial environments


• Configurable FIFO buffers optimize data throughput for varied communication patterns


• Bus-powered operation requires no external power supply

Typical Applications

• Industrial automation and process control


• Laboratory instrument integration and data acquisition


• Embedded systems requiring serial device connectivity


• Multi-device sensor networks over RS-485 networks

Compatibility & Integration

• Operating Systems: Windows, macOS, Linux


• Software APIs: NI-Serial drivers, NI-VISA


• Compatible with standard serial communication libraries