After sending INST:SEL, it is recommended that you verify the command by sending INST:SEL? or
SYST:ERR?, otherwise the next commands will go to the wrong power supply.
12.4.2. Global Commands in a Multi-drop Chain
The GLOBAL commands affect all of the chained supplies at the same time, including the LAN supply
There are differences between a normal SCPI command (in section 11) and a global command.
The differences are:
- There is no SYSTEM:ERROR? response message (see section 11.8.1) if one or more supplies cannot
execute a global command.
- It is required that the user’s application add a 200 millisecond delay after a global command before
sending any other messages. This is because there is no feedback from the multi-drop chain to indicate
the command is still being processed.
- There is no query version of these commands. Global settings must be queried by selecting one power
supply and reading it’s setting.
- The error and status registers operate differently. See section 12.4.10 for details.
- The global commands are not SCPI compliant.
The global commands do not affect which power supply has been selected using the
INST:SEL command.
For example, if the following commands are sent:
INST:SEL 4
:VOLT 50
GLOB:VOLT 70
(wait 200 mSec)
:VOLT 90
then all the supplies on the multi-drop chain will be set to 70 volts except the supply at RS-485 address 4
will be set to 90 volts (after the global command, another
INST:SEL was not required)
12.4.3. Selecting a Supply
This command will select one power supply in a multi-drop chain. Subsequent commands and queries
will operate only on that supply, until a new one is selected. At power-up, the LAN supply is automatically
selected
Syntax:
INSTrument:SELect <nn>
Parameter: <nn> is the supply’s RS-485 address. It is a number from 0 to 30
see sections 12.2.1 and 12.2.2 for set-up instructions
Example:
INST:SEL 6
Query: INST:SEL? will return 06 in the example
Errors:
SYSTEM:ERROR? may return errors including:
-241,”Hardware missing;address nn”, if nn is an invalid address
GLOBAL COMMANDS
The following global commands affect all power supplies on a multi-drop chain. See section 12.4.2 for
requirements. There is no query version of these commands
12.4.4. Global Set the Voltage Limit
This is the global version of the :VOLT command in section 11.2.1
Syntax:
G L O B a l:V O L T a g e[:L E V e l][:I M M e d i a t e][: A M P L i t u d e] < n n . n n >
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