17
WIKA operating instructions premium pressure transducer, model CPT9000
0020504001G 10/2019 EN
EN
Operation
6. Operation
6.1 General Operation
The CPT9000 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.
Due to the nature of the various RS-485 converters available there may be communication issues.
We have determined that our devices work with the ACCES I/O PRODUCTS devices. At this
time we are not in a position to comment on any other make of RS-485 converters and their
suitability for use with our products.
6.1.1
Command and Query Format
C o m m a n d s
must be sent in ASCII format and terminated with a carriage return (<CR>) optionally 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 CPT9000, the commands must be preceded by a “
#
”, an address or a “
*
”. 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 CPT9000, 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 CPT9000 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:
!
Caution
