Emerson Rosemount 1066, Инструкция по эксплуатации

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Instruction Manual Section 9: Calibration
LIQ-MAN-1066 April 2017
Calibration 77
Zeroing the Sensor
The adjacent screen will appear during Zero Cal. Be sure sensor has been
running in zero solution for at least two hours before starting zero step.
The adjacent screen will appear if In Zero Cal is successful. The screen will
return to the Amperometric Cal Menu.
The adjacent screen may appear if In Zero Cal is unsuccessful. The screen
will return to the Amperometric Cal Menu.
In Process Calibration
The adjacent screen will appear prior to In Process Cal
If the In Process Cal is successful, the screen will return to the Cal sub-menu.
The adjacent screen may appear if In Zero Cal is unsuccessful. The screen
will return to the Amperometric Cal Menu.
Calibration – Total Chlorine
Total chlorine is the sum of free and combined chlorine. The continuous determination of total
chlorine requires two steps. First, the sample flows into a conditioning system (TCL) where a pump
continuously adds acetic acid and potassium iodide to the sample. The acid lowers the pH, which
allows total chlorine in the sample to quantitatively oxidize the iodide in the reagent to iodine. In
the second step, the treated sample flows to the sensor. The sensor is a membrane-covered
amperometric sensor, whose output is proportional to the concentration of iodine. Because the
concentration of iodine is proportional to the concentration of total chlorine, the transmitter can
be calibrated to read total chlorine. Because the sensor really measures iodine, calibrating the
sensor requires exposing it to a solution containing no iodine (zero standard) and to a solution
containing a known amount of iodine (full-scale standard). The Zero calibration is necessary
because the sensor, even when no iodine is present, generates a small current called the residual
current. The transmitter compensates for the residual current by subtracting it from the measured
current before converting the result to a total chlorine value. New sensors require zeroing before
being placed in service, and sensors should be zeroed whenever the electrolyte solution is
replaced. The best zero standard is deionized water. The purpose of the In Process Calibration is to
9.6.1.1
9.6.1.2
9.6.2
1.234 µS/cm 25.0 ºC
S
N
Zero Cal
Sensor zero done
1.234 µS/cm 25.0 ºC
S
N
Zero Cal
Zeroing
Wait
1.234 µS/cm 25.0 ºC
S
N
Zero Cal
Sensor zero failed
Press EXIT
1.234 µS/cm 25.0 ºC
S
N
InProcess Cal
Wait for stable
reading.
1.234 µS/cm 25.0 ºC
S
N
InProcess Cal
Calibration
Error
Press EXIT