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WIKA operating instructions process pressure transducer, model CPT6020
0020507001F 05/2019 EN
EN
Operation
6. Operation
6.1 General Operation
The CPT6020 transducer can be ordered with either an RS-232 or RS-485 full duplex output. The communications protocol is
defaulted to 57600,N,8,1. The baud rate can be changed via remote commands. Connector pinouts and RS-232 and RS 485
cable connections are shown in Figure 5.1.2. The transducer has multiple command sets with which it can communicate with the
host. These are set through the CMD_SET command.
6.1.1
Command and Query Format
Commands must be sent in ASCII format and terminated with a carriage return (<CR>) followed by a linefeed (<LF>). Commands
are not case sensitive. Query strings are terminated with a “?” prior to the termination character(s). If the transducer is put in a
burst output mode, the output of the transducer is in a binary output mode. The host communications program must synchronize
with the output of the transducer. The transducer’s output to a pressure value query is programmable depending on what the user
wants in the output string.
6.1.1.1
RS-485 Command and Query Format
On RS-485 versions of the CPT6020, the commands must be preceded by a “
#
”, an address or a “
*
”, and a space. In RS-485 the
ADDRESS command sets the address in ranges from “0” to “9” and “A” to “Z”. The global address character is the “
*
”. When data
is required for a command, a space (only) should delimit command and data fields.
6.1.1.2
RS-232 Command and Query Format
On RS-232 versions of the CPT6020, the “
#
” or address character is not necessary to precede the command for the Sensor
command set. But, the Mensor Legacy command set still requires a proceeding “
#
” and address character. With the default
sensor command set in RS-232, the start character and address character are not required.
6.1.1.3
Command Error Detection and Debugging
The CPT6020 has built in responses to correct and incorrect data. The responses can be used to help debug the software. In the
Sensor command set, the device will return “Ready” in response to a valid data command. If the device is in the Mensor Legacy
command set, an “R” will be returned in response to valid data. If the data is determined to be invalid, the Sensor command set
will return “Invalid Data”. The Mensor Legacy command set will still return an “R” character when invalid data is sent. This is a
limitation of the Mensor Legacy command set. The Sensor command set will return “Unknown command” if the command is not
found, while the Mensor Legacy command set will ignore it and not respond. This paragraph is summarized below in the following
table:
Mensor Legacy Command Set
Case
Return Value
Valid data command
“R”
Invalid data command
“R”
Invalid command
Nothing
Sensor Default Command Set
Case
Return Value
Valid data command
“Ready”
Invalid data command
“Invalid Data”
Invalid command
“Unknown Command”
Query Customer password protected command
“User Password Needed”
Table 7.1.1 Command set returns for given cases
Also, it is important to note that when sent data is determined to be valid, the value will be stored in RAM. Only after the SAVE
command is sent is the data saved permanently. This applies to all command sets.
