Appendix 1

1.1 Communications Protocols.

1.2 RS232 Command communications.

Data is transmitted upon request in normal operation and calibration modes.

Transmission is suspended during boot and in edit mode, and in the case of an error. The protocol can be either in a terse format (i.e.D) or in instruments supporting the extended readable format (i.e. Data).

Command : DTE to instrument Format : Command=xxx.xx <CR><LF>.

Command	function	reply
Data=x<CR><LF>.	Request for diagnostic data. Optional =”x” is specifying the required line of data	D2 Ref=1234b D1 M1= 2222b
Reading=x<CR><LF>.	Request for Reading. Optional =”x” is specifying the required line of reading in sensor with multiple data sets.	R2 CO2=0.01r R1 H2= 20.0%
Zero=xxx.xx<CR><LF>.	Request to zero the sensor assumed 0.00. Optional. =”xxx.xx” is specifying the zero point data.	Z1 pass or Z1 fail
Span=xxx.xx<CR><LF>.	Request to Span the sensor. data assumed 100.00% of sensors span. =”xxx.xx” is optional specifying the Span point data. Otherwise.	S1 pass or S1 fail

=XXX.xx is optional and must be proceeded by an “=” and is used to set the value of the action.

The message is: Reqest Y Quantity = xxxxx unit <CR><LF>.

Request: is the first character of the command D R S Z

Y: is the line number for the data.

The highest line number is always presented first hence line 1 is always the last data line of a communication.

Extension is when “x” is specified the only that line number will be returned.

Quantity: is one of H2 CO CO2

xxxx: is the measured quantity. The resolution is the same as the display:

Unit: is one of % percent r compensation ratio

The compensation ratio is the diagnostic data for instruments with a secondary gas background. When requested as a data it will return the present ratio for compensating the primary measured gas “R1”

I.e. for H2 in N2 with a secondary gas of CO2

D1 CO2=0.069r If you know the concentration of the CO2 can calculate the correction in the H2 reading as H2- ( CO2 * 0.069)

In over-range condition (when the display shows ‘HI’) xxxxx will be ‘+++++’ In under-range condition (when the display shows ‘LO’) xxxxx will be ‘-----’

Controller.	Sensor
Reading	R1 H2= 98.5%	Instrument request a reading
Span=99.0	S1 Pass	Controller requests a span setting of 99.0%
Reading	R1 H2= 99.0%

I.e. this would set the present instrument reading to 99.0% The unit “%” is assumed to be the same as the reading.

Error messages

Error messages take the form ‘? xx’ where ‘xx’ is a numeric code as explained below Comms. Errors:

Code	Error	Description
90	Buffer overflow	More than 15 characters were received without message terminator (<CR><LF>). Any subsequent characters will begin a new message.
91	Message timeout	10 seconds has elapsed since the last character was received without message terminator.
92	Bad opcode	Message was received correctly terminated but not understood (e.g. ‘Fred=1<CR><LF>’)
93	Bad operand	Message was received correctly terminated and understood but the line number wasn’t (e.g. ‘Reading=Q<CR><LF>’).

System errors

Code	Error	Description
71-76	NVRAM CRC error	Three areas exist (1,3 & 5) each with a backup (2,4 & 6). Area 1 contains user parameters i.e. calibration data and the backup is write protected so if this area is restored user calibration etc is LOST. Error 71 will be reported in response to any read request until either a calibration is performed or the instrument is rebooted. Areas 3 & 5 are read only so they can be silently restored. Errors 73 & 75 therefore should never be reported, although they exist internally until they clear themselves. Errors 72,74 & 76 will be reported in response to any read request and cannot be cleared.
77- 78	TCD curve error	In reading curve data from EEPROM the instrument has attempted to read beyond the ends of the curve.
79	Wrong block no.	The serial numbers of the Nitriding Sample Cell stored in areas 1 & 5 (in separate devices) do not match
80	UART missing/error.	For debugging only. Since the only interface available is RS232, this error can never be reported!
81	Reserved	For external EEPROM not found.