TAMS 1800 Series, Руководство по установке и эксплуатации, Страница: 12 / 28

USB Power Considerations
The TAMS 1800 Series Switches are powered from the USB bus. This power must
always be applied, otherwise the switches would lose their state. Therefore, power
management should be disabled in applications where the switches cannot be powered
down. Power management on the PC can be disabled via Power Options in the Windows
Control Panel.
Connecting switches to other switches
TAMS 1800A series switches can be interconnected via the “Analog Bus” on the rear of
each unit. This bus contains four analog lines, two grounds or commons, a trigger in, and
a trigger out. The switches can be “daisy-chained” together until you run out of USB
devices (127 max, 5 levels of hubs).
An example part number for the interconnect cable is Digi-Key A9BBG-0803F-ND.
For operation above 42V, note that a second level of insulation is required for this
interconnect cable. Typically, the switches will be mounted inside of a chassis or rack,
which could provide the necessary screw access for the second level of insulation.
With most signal switches, there would be a concern about connecting too many switches
together, as the signal path capacitance increases, especially for large matrix switches.
Note, however, that for the TAMS 18xx switches, each switch can be separately
connected or disconnected from the “Analog Bus”, greatly reducing stray capacitance.
For more information, see TAMS Application Note “AN 1801: Switching in the real
world.”
Connecting switches to your Product Under Test
The various switch modules have a variety of different connectors to make connections
out to your product under test. The switch modules that use high density “D-
subminiature” connections can easily be mated to standard cables available from
www.l-
com.com or other vendors. The switch modules that use screw terminal blocks are easily
connected with custom wiring. Note that a second level of insulation must be provided
for custom cabling that contains any voltages above 42V.
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