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USBTMC vs USB

Last Updated: Aug 26, 2019 03:04PM PDT
BK Precision offers a variety of interfaces for communication, and within the USB interface, there are a couple of device classes: USB-Virtual COM and USBTMC.

USB-Virtual COM device class enables our products to be remotely controlled as if it were a serial port, hence the virtual part in the name. The drivers provided for each product create a "virtual COM port". The disadvantage of this interface is that there is the need to install drivers for each instrument. The advantage is that most programming languages support this type of class.

USBTMC, this class of USB is dedicated for instruments. TMC stands for Test and Measurement Class. It is built on top of the USB standard with the intention of replacing IEEE-488 GPIB standard. To use USBTMC, the user will need to install a VISA package (BK PRECISION uses National Instruments VISA). Virtual Instrument Software Architecture (VISA) is a standard for configuring, programming and troubleshooting instrumentation systems. The disadvantage of this class is that some languages might not support it, even though nowadays that is changing. The advantage is that there is only one VISA to install for any products that are USBTMC compatible.

Some of our products do not have USB-Virtual COM, but have USBTMC. If the user requires virtual COM, one possibility to circumvent this is to see if there is an RS-232 port available in the product and use that interface. If there is no serial port in the computer, then an adapter RS-232 to USB should be acquired.
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