Much has been said about the integration of PXI products with LXI and VXI to create hybrid test systems, but less has been said about combining PXI and USB products in a test system, writes David Owen from Pickering Interfaces.
USB is a common interface on both consumer and professional products, and ubiquitous on many mobile devices. That means that it may be native control connection on a device that needs testing - so a test system ideally needs the capability of supporting USB.
The USB standard has also been used in creating elegant and cost effective solutions for test purposes, for example USB based RF power meters are available from a number vendors while others have created data acquisition systems and even basic scopes and DMM's.
These instruments often benefit from being able to be supported by USB power alone, avoiding the need for AC power sources. They are therefore typically instruments which have modest power requirements and size.
They can also typically be placed more directly on a connection to be measured, for example a power meter sensor will be positioned at the RF connector, rather than be fixed in a chassis.
USB devices can be placed closer to the point of measurement than devices that are chassis mounted as long as they are within the reach a distance of 5m.
This means that USB devices can bring a different set of features to a test system, and as with LXI there are advantages in being able to add USB to a system with PXI content.
Pickering Interfaces has provided PXI-based options for USB switching, the 40-737 for example offers a USB switch which allows a single USB connection to be switched to one of eight USB devices.
The 40-738 is a single slot 3U PXI module that combines an 8-port USB 2.0 hub and USB data/power switching to provide a connection between the PXI controller's PCI interface (the PXI backplane) and USB products.
The PXI controller recognises the USB device and installs the vendor's drivers as though the product was connected to the controller's native USB ports.
It offers a means to independently connect or disconnect the USB data and power connections, allowing the user to simulate fault conditions on the USB interface or to completely disconnect the USB product.
