The multiplex or scan topology is used to connect one instrument to multiple UUTs or multiple instruments to a single UUT. The connections can be sequential (such as scan in the figure below) or non-sequential (such as multiplex in the figure below). In addition, multiplexing permits more than one simultaneous connection. For example, routing the UUT output to an AC voltmeter and to a frequency counter.
The 1:X configuration is sometimes used to connect a source to many points or a single point to many measure instruments. The X:1 configuration is used to connect several sources to a single point or many points to a single instrument. To synchronize source and measurement connections, a 1:X/X:1 pair can be switched together.
As shown in the figure below, the scan topology is equivalent to a rotary selector switch. With this type of topology, there are two common versions:
Make-Before-Break, which makes the new connection before breaking the existing connection.
Break-Before-Make, which breaks the existing connection before making the new connection.
Either of these types can be implemented in a test system. Unless otherwise indicated, the non-shorting type is assumed.
Marvin Test Solutions' GX6264 is Multiplexer/Scanner that can be used for the Scan Topology. All products are of the Break-Before-Make version, although it is possible to switch multiple points simultaneously using different Scan Groups.
