Scan Lists - Racal Instruments 1256 Manual

1256 User Manual

Scan Lists

Advanced SCPI Operations 8-14
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The 1256 may be programmed to sequence through a list of
channels. This feature is known as a "Scan List".
When a Scan List is used, the user defines a list of channels to
operate. Each time a trigger is received by the 1256, the presently
closed channel is opened, and the next channel on the list is
closed. This capability may be used in conjunction with a Digital
Multimeter (DMM) or other measurement device to allow a group
of measurements to be made without having to program the 1256
for each relay operation.
For example, without the Scan List feature, for each DMM reading,
you must:
A) Program the 1256 to close a channel
B) Wait/Query the 1256 to ensure the channel is closed
C) Program the DMM to take a reading
D) Program the 1256 to open a channel
With the Scan List feature, the DMM and 1256 are programmed to
trigger each other for each DMM reading. After this, sending a
trigger to the 1256 intiates the cycle of:
Close Relay, Take DMM Reading, Open Relay
automatically. When all of the desired readings have been made,
the DMM may be read to obtain the group of measurements. This
method usually results in increased measurement rate by
minimizing the command processing time of the instruments
involved.
To set up the Scan List, the programmer must:
A) Program the 1256 to define the list of channels to scan
through, using the SCAN command.
B) Program the 1256 to select an input trigger source. This input
trigger source should be the external trigger input. The
TRIGGER:SOURCE command is used to select the input
trigger.
C) Program the 1256 to generate a trigger each time a relay is
closed. The output trigger must be enabled, through the
OUTPUT:TRIGGER command.
D) Program the DMM (or other instrument) to select an output
trigger source. The output trigger source should be the input
trigger source of the 1256, as indicated in step (B) above.
E) Program the DMM to select an input trigger source. The input
trigger source should be the output trigger line of the 1256,
as indicated in step (C) above.
F) Program the DMM to select a trigger count, which sets the
Publication No. 980855 Rev. A
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