Agilent Technologies Helium Leak Detector
DRAFT 12/11/17
139
Appendix A. Communications Protocol
This appendix defines the technical specifications for the RS-232 protocol used with the
leak detector and describes the customer-configured inputs/outputs.
A.1 Protocol (RS-232)
RS-232 ports operate at 9600 baud, 8 bits, no parity, and one stop bit.
All characters transmitted to the leak detector are echoed by the leak detector. Commands,
inquiries, and strings of both commands and inquiries must be terminated by a carriage
return <CR>; the carriage return is echoed as a space character.
The maximum length of the input is 80 characters; if no carriage return has been received
before the 80th character, execution of the command string begins anyway.
Words that begin with:
❑ ? are inquiries for the controlling device to determine the current state or value of a
leak detector parameter.
❑ PUT- are commands for the controlling device to set the current state or value of a
volatile leak detector parameter.
❑ INIT- are commands for the controlling device to set non-volatile leak detector
parameters.
Other commands do not require a parameter and do not begin with any special characters.
Successful inquiries respond with data, followed by a space, then: ok<CR><LF>, as
specified in the tables of this appendix. Unsuccessful inquiries respond with the offending
inquiry followed by a space, then: #?<CR><LF> (line feed, <LF>).
Inquiries, parameters, and commands can be concatenated. Each word or numeric
parameter is followed by one or more spaces. The string is terminated by a <CR>, which
causes execution to begin.
Successful strings respond with the specified data for the input inquiries in the order the
inquiries were issued, followed by: ok<CR><LF>.
Unsuccessful strings respond with the first offending command followed by a space,
then: #?<CR><LF>. All commands and inquiries following the failed word are ignored;
all parameters are discarded.
Table A-1 on page 143, Table A-2 on page 146, Table A-3 on page 149, and Table A-4 on
page 149 outline the available control and query commands.
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