USB Test and Measurement Class or USBTMC instruments are defined initially to allow General Purpose Interface Bus-style (GPIB-style) communication over USB using USBTMC compliant Virtual Instrument Software Architecture (VISA) layers. The standard defines protocols that are used to send instrument command messages to an instrument and read back response messages. Most USB-based instruments available today adhere to the USBTMC standard. These instruments are mostly programmed via Standard Commands for Programmable Instruments (SCPI) or similar text messages, comparable to what you would expect from a GPIB instrument.
Keysight IO Libraries will be able to enumerate and discover the USBTMC instruments by making use of the standard USBTMC class device driver in windows. These USBTMC instruments will be detected as “USB Test and Measurement Devices” in the windows device manager and appear in the Keysight IO Libraries with a VISA address assigned, as shown in Figure 1. With that, users can start to communicate with these USBTMC instruments using the VISA address. This article will demonstrate how a mechanism can emulate a USBTMC instrument on a Microsoft Windows computer and work exactly like a USBTMC instrument without having any USB devices plugged in to the Microsoft Windows computer.