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MODEL 5081-A
SECTION 10.0
CALIBRATION - FREE CHLORINE
10.6 DUAL SLOPE CALIBRATION
Figure 10-2 show the principle of dual slope calibration. Between zero and concentration C1, the sensor response
is linear. When the concentration of chlorine becomes greater than C1, the response is non-linear. In spite of the
non-linearity, the response can be approximated by a straight line between point 1 and point 2.
dual slope calibration is rarely needed. It is probably useful in fewer than 5% of applications.
1. Be sure the transmitter has been configured for
dual slope calibration. See Section 7.6.
2. Zero the sensor. See Section 10.2.
3. Place the sensor in the process liquid. If auto-
matic pH correction is being used, calibrate the
pH sensor (Section 13.0) and place it in the
process liquid. If manual pH correction is being
used, measure the pH of the process liquid and
enter the value. See Section 7.8. Adjust the
sample flow until it is within the range recom-
mended for the chlorine sensor. Refer to the
sensor instruction sheet.
4. Press CAL on the remote controller. Press NEXt.
5. the
SEnSor CAL
prompt appears. Press ENtER.
6. the
CAL Pt 1
prompt appears. Adjust the chlorine concentration until it
is near the upper end of the linear range of the sensor. Press ENtER.
7. the
tiME dELAy
message appears and remains until the sensor read-
ing meets the stability criteria set in Section 7.6. to bypass the time
delay, press ENtER.
NOTE
As soon as the stability criteria are met (or ENtER is pressed
to by-pass the time delay), the transmitter stores the sensor
current. therefore, if the chlorine level in the process liquid
drifts while the sample is being tested, there is no need to
compensate for the change when entering test results.
8. the
GrAb SPL
(grab sample) prompt appears. take a sample of the
process liquid and immediately determine the concentration of free
chlorine in the sample. Press ENtER.
CALIBRAtE
Cal pt1
EXIt
NEXt ENtER
CALIBRAtE
Grab spl
EXIt
ENtER
CALIBRAtE
Sensor Cal
EXIt
NEXt ENtER
CALIBRAtE
time delay
EXIt
NEXt
FIGURE 10-2. Dual Slope Calibration