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Interfacing with a computer:
Send a single character to the instrument and it will execute the corresponding
command as follows:
1 = press MODE.
2 = press CAL.
3 = press Ù.
4 = press Ú.
5 = press SET.
6 = press HOLD.
7 = press RES.
8 = press PRINT.
?
= send display to computer.
+ = keyboard on (manual operation remains possible).
-
= keyboard off (manual operation disabled).
V = start the input of a value (only valid in certain routines).
Follow exactly the same measuring or calibration procedures, as described in
this manual, to include any desired command in your computer data-acquisition
program. This example continuously prints the measured values on the computer
screen:
10
ON ERROR GOTO 70
20
OPEN "COM1:2400,N,8,2" AS #1
30
PRINT #1,"8"
40
INPUT #1,V$
50
PRINT V$
60
GOTO 30
70
RUN
Input of a value:
The direct input of values ("V" command) is only possible when the instrument is
running a routine where also a manual input of these values could be made. If not,
it will ignore any "V" command from the computer!
Examples of allowed routines are:
• temperature input (e.g. manual temperature compensation).
• control parameter input such as Low, High, ...
• time settings.
• input of manual buffer values.
Examples of NOT allowed routines are:
• during measurements.
• when values have to be selected rather than changed (e.g. buffer values in
memory).
• while an electrode is being calibrated.
A 16-bit value (2's complement) should be transmitted in the following sequence:
1st character
=
"V" (start a value input)
2nd character
=
highest byte of the value in ASCII
3rd character
=
lowest byte of the value in ASCII
4th character
=
checksum of 2nd and 3rd character in ASCII
5th character
=
LF, linefeed (ASCII-10)
When a correct checksum has been received, the instrument will send a confir-
mation character "!" to the computer. If not, a question mark "?" is sent. Both are
eventually preceded by the identification number. This example makes the com-
puter to enter the value "1000" on instrument #7, in the sophisticated mode:
1000 = (H-byte 3)(x 256) + (L-byte 232)
10
OPEN "COM1:2400,N,8,2" AS #1
20
PRINT #1,"V";
30
PRINT #1,CHR$(3);
40
PRINT #1,CHR$(232);
50
PRINT #1,CHR$(235);
60
PRINT #1,CHR$(10);
C831 • C832 • C833 • C835 • C838
'makes sure no error occurs
'prepares computer input
'PRINT button pressed
'measured values transmitted
'received values printed
'repeat procedure
'prepares communication port
'start a value input
'highest byte of value
'lowest byte of value
'checksum of both bytes
'LF, closes command
Computer
20 / 74
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