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Comments Isolation. The direct terminals provide a more accurate measurement than
the tree terminals or the analog bus connector as the signal does not have to
travel through the extra FET switches. The
SCAN:PORT NONE command
opens the tree isolation switches and isolates the direct terminals from the
tree terminals and the analog bus connector.
The default value of
SCAN:PORT is NONE for reset and power-on. If you
have not specified a different
SCAN:PORT since reset or power-on, you do
not need to execute this command. You can also use the direct terminals
with
SCAN:PORT ABUS. The signal for a given closed channel will then
be available at the direct terminal for that bank, the A tree terminal and the
analog bus connector.
Closing Channels. The FET multiplexer module only allows one channel
per card to be closed at a time, except for
SCAN:MODE FRES (4-wire
resistance measurements) where two channels are closed. You can close a
channel on two different cards in the same instrument at the same time.
The
SCAN <channel_list> command allows you to specify a list of channels
to be closed sequentially. The FET multiplexer module uses a
break-before-make procedure, so closed channels are opened before the
next one on the list is closed. The channels are advanced according to the
TRIGger mode selected.
Query Open/Closed Channels. The
CLOSe? <channel_list> and OPEN?
<
channel_list> commands determine if the channel(s) in the channel list are
open or closed, respectively. (The query command does not determine if, in
the event of a hardware failure, the channel remains open/closed.) For
example, to determine if channel 109 is closed, execute:
CLOS? (@109)
A response of "1" indicates the channel is closed, and a "0" indicates the
channel is open. The reverse is true for the
OPEN? <channel_list>
command. The response for the OPEN? and CLOSe? commands are:
CLOS? 1 = Closed
0 = Open
OPEN? 1 = Open
0 = Closed
To find out which channel on a card is closed, use a channel list for the card.
CLOS? (@100:115)
and enter the response into a string variable. If channel 09 is closed, the
response will be:
0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0
NOTE: You must read the response after sending a query command or
the switchbox will generate an error.
Chapter 3 Using the HP E1351A/53A FET Multiplexer Modules 33