22 OI/ATS430–EN Rev. H
| Aztec ATS430 | Turbidity sensor
6.4.7 Manual coefficient
This calibration mode enables the user to enter directly the
coefficient that relates the turbidity of the sample to its
suspended solids content. The sensor uses the following
equation to calculate suspended solids content from turbidity
(see Fig. A.2, page 27):
SS = T/a
Where:
SS is the suspended solids content in the required units
(mg/l or ppm),
T
is the turbidity in NTU
a is the coefficient.
If a set of data points of turbidity and suspended solids, the
coefficient can be calculated by plotting the suspended solids
(y-axis) against turbidity (x-axis) and fitting a straight line with
an intercept of 0. The calibration coefficient is the slope from
the linear fit of the data.
1.
To enter a coefficient, select
Manual Coefficient
from the
Calibration Type
screen and press the
key (below the
Next
prompt).
2. Press the
key (below the
Edit
prompt) to enter the value
of the coefficient and press the
key (below the
OK
prompt) when complete.
3. The
Calibration Complete
screen is displayed. Press the
key (below the
Next
prompt) to return
to the main menu.
The calibration is now complete.
6.5 Calibration log
The calibration log stored in the sensor holds a record of the last
15 calibration operations undertaken on the sensor. To view the
calibration log in the transmitter, logs must be enabled first.
Refer to the AWT440 transmitter manual (OI/AWT440-EN) for
details of how to enable logs.
Once logs are enabled, a calibration log page exists for each of
the sensors connected to the transmitter. To access the
calibration log, press the View key on the transmitter keypad
(the first calibration log is displayed):
Use the group key in the keypad to cycle through the calibration
logs for each of the sensors. The log shows the result of the last
15 calibration operations undertaken. The result can be:
—
Calibration aborted
: if calibration is stopped (by the
user) part of the way through
—
Calibration failed
: the log entry displays the reason for
the calibration failure
—
Verification successful
: if the sensor passes verification
—
Verification failed
: if the sensor failed verification
—
Calibration successful
: the log entry displays the new
calibration parameters
Each entry displays the date and time the operation was
performed. Note that the date and time are taken from the
transmitter. To ensure the date and time stored in the log are
accurate, ensure the date and time set in the transmitter are
correct.
Suspended Solids
Next
Edit
Calibration Type
Manual Coefficient
Suspended Solids
Next
Edit
Manual Slope
0.0000
Fig. 6.3 Calibration log for Sensor 1, showing the result of different
calibration and verification operations
2016-02-12
09:45:40
CAL
Calib. Log S1
No. Event Date Time
01
02
03
04
05
Slope Low
1.01 /0 NTU
Cal Aborted
Verification
Verification
2016-02-12 09:42:32
2016-02-12 09:40:33
2016-02-12 09:39:16
2016-02-12 09:37:59
2016-02-12 09:36:13
