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What Is USBTMC and How Can I Communicate with My USB Instrument?



Primary Software: Driver Software>>NI-VISA
Primary Software Version: 3.2
Primary Software Fixed Version: N/A
Secondary Software: N/A

Problem:
What is USBTMC and how can I communicate with my USB instrument using NI-VISA?

Solution:
USBTMC stands for USB Test & Measurement Class. USBTMC is a protocol built on top of USB that allows GPIB-like communication with USB devices. From the user's point of view, the USB device behaves just like a GPIB device. For example, you can use VISA Write to send the *IDN? query and use VISA Read to get the response. The USBTMC protocol supports service requests, triggers, and other GPIB specific operations.

USBTMC allows instrument manufacturers to upgrade the physical layer from GPIB to USB while maintaining software compatibility with existing software, such as instrument drivers and any application that uses VISA. 

It is important to note that not all USB devices are USBTMC compliant. The device manufacturer has to add the support in the device firmware to support USBTMC. Traditional instruments with USB ports (such as DMMs and scopes) are most likely to support USBTMC. Refer to the instrument's documentation to determine if it is USBTMC compliant.

NI-VISA 3.0 or later allows you to communicate with USBTMC compliant devices as a controller. To use such a device, connect it to your computer. If NI-VISA is properly installed, the device will be installed as a USB Test & Measurement Class Device. Open NI Measurement & Automation Explorer (NI MAX), and the new device will now appear under Device and Interfaces»USB Devices. You can then use this resource name as you would use any GPIB resource.

On Macintosh and Linux, connect the USBTMC device. If NI-VISA 3.2 (or later) is installed properly, the device will be installed as a USB Test & Measurement Class Device. To verify the device was installed, open VisaConfig by navigating to Applications»National Instruments»VISA»VisaConfig. VisaConfig will list the USBTMC device under USB Resources. You can use this resource name as you would use any GPIB resource.

For more information on the syntax of the resource name, refer to the description for viOpen in the NI-VISA Help, linked below

Related Links:
Drivers and Updates: NI-VISA
Product Reference: NI-VISA Help
KnowledgeBase 325APJ2Y: How Can I Communicate With a Device Using NI-VISA USB Raw Mode?
NI Support Tutorial: USB Instrument Control Tutorial

Attachments:





Report Date: 10/02/2003
Last Updated: 05/11/2016
Document ID: 321A2A2Y

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