Emerson Rosemount Analytical HART 5081-A-HT, Instruction Manual

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MODEL 5081-A SECTION 11.0
CALIBRATION - TOTAL CHLORINE
11.4 DUAL SLOPE CALIBRATION
Figure 11-3 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 7.8.
2. Zero the sensor. See Section 11.2.
3. If the sensor was just zeroed, place the
reagent uptake tube back in the bottle. Once
the flow of reagent starts, it takes about one
minute for the sensor current to begin to
increase. It may take an hour or longer for the
reading to stabilize. Be sure the sample flow
stays between 80 and 100 mL/min and the
pressure is between 3 and 5 psig.
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 7.8. 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 total
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 11-3. Dual Slope Calibration