Signal Path Overview

A core concept in HIL system design is the signal path — the physical and logical route that a signal takes from the DUT to the point of acquisition, or from the point of generation back to the DUT. Each signal path is defined by the hardware components it traverses and by the capabilities required to support a specific type of I/O operation.

Most signal paths begin at a signal generation or acquisition point, which typically falls into one of the following categories:

• Discrete I/O: Analog, Digital, PWM, Resistor Simulation, etc.
• Communication Buses: CAN, LIN, Automotive Ethernet, FlexRay, RS485, EtherCAT, Ethernet, and others
• Instrumentation I/O: DMMs, Oscilloscopes, Function Generators, Network Analyzers, Signal Generators, etc.

Each of these I/O types is defined by a set of parameters — such as channel count, voltage/current ranges, impedance, bandwidth, sample rate, resolution, accuracy, isolation, and more. In NI HIL systems, these signal types and specifications are typically implemented using PXI modules.