11
5.2.5 Retrieving the slope values
A slope can only be calculated between two calibration points. When retrieving a slope after only a
single point calibration the returned values will represent 0%.
Normal slopes between two consecutive pH buffer solutions should be between 105% – 95%.
Slopes outside these values, can indicate a polluted or aging ISFET sensor /reference electrode.
Although calibrations and measurements can be performed the measured values may be less
accurate. In this case, if cleaning the sensor / reference electrode does not resolve the slope issue be
sure to replace the ISFET sensor and/or reference electrode.
Retrieve slope value:
Send the command bytes:
000!<CR>
Wait for the module to return the slope values, receive bytes: ABCDEFGHIJKLMN
Data ABCDEFGHIJKLMN marks the byte position. Values in bytes are needed for decoding.
Byte position
A
B
C
D
E
F
G
H
I
J
K
L
M
N
Byte value
001 byte byte 002 byte byte 003 byte byte 004 byte byte 013 010
Decode received sequence if e.g.:
Byte position
A
B
C
D
E
F
G
H
I
J
K
L
M
N
Received
bytes
001 000 000 002 015 052 003 000 000 004 000 000 013 010
Slope positions:
Protocol
Decode
Result
slope between pH 2 and pH 4
B*64+C
000
*64+
000
0%
slope between pH 4 and pH 7
E*64+F
015
*64+
052
101.2%
slope between pH 7 and pH 10
H*64+I
000
*64+
000
0%
slope between pH 10 and pH 12
K*64+L
000
*64+
000
0%
ADGJ = n/a
Содержание A120-001
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