B&K Precision 5491B - Manual - Manual (Page 42)

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 600
Note: Factory default baud rate is 9600.
Refer to section 4.5.2 for details on configuring baud rate settings on the multimeter.
5.2.4 Software Protocol
Please refer to the content below before programming application software.
1. For command syntax and format, refer to Chapter 6 Command Reference.
2. The controller transmits the command using the ASCII code with or as the termination
character. The multimeter executes the command after the termination character is received.
3. The character received by the multimeter will be sent back to the controller again. The controller will
not send the next character until the last returned character is received correctly from the meter. If
the controller fails to receive the character sent back from the meter, the possible reasons are listed
as follows:
 The serial interface is not connected correctly.
 Check if the same baud rate is selected for both the meter and the controller.
 When the meter is busy with executing a bus command, it will not accept any character from
the serial interface at the same time. So the character sent by controller will be ignored. In order
to make sure the whole command is sent and received correctly, the character without a return
character should be sent again by the controller.
4. The multimeter only sends information under following two conditions. The first is when a character
is received normally; the meter will send the character back as a handshake. The second is when a
query command is received; the meter will send the query response information.
5. Once a query command is received, the meter will send the query response information
immediately even if the rest of the commands have not been finished. So if the command includes
two queries, the controller should read the query responses twice. One query is recommended to be
included in a single command.
6. A query response is sent out in ASCII codes with the preset termination character.
7. For some commands that will take longer time to execute, for example reset command, the
controller should keep waiting to avoid the next command being lost when the meter is executing
the former command.
5.3 Data Format
The meter outputs the measurement results using the ASCII character string format via the RS232 serial
interface. The data format is described in the following Figure 5-3.
SD.DDDDDDESDDD
S: +/-
D: number 0 to 9
E: exponent sign (“+”is omitted)
: New Line, ASCII code is 10
Figure 5-3 Data Format