YOKOGAWA FC400G, Руководство пользователя, Страница: 68 / 91

< 7. Calibration >
7-7
IM 12F5A1-01E
the mg/l (or ppm) indication to blink during calibration operation. When the span calibration is
completed normally, “CAL.END” appears.
Note: If an error occurs during calibration operation, “END.E5” or “END.E7” is displayed in the message. When this message is
displayed, take countermeasures, referring to Sec. 7.4.
(5) Press the
YES
key to end the calibration and switch the FC400G to the MEAS mode.
Press the
YES
key to switch the FC400G to the <MEASURE> or <HOLD> mode (“HOLD.
ON” in the message display). When “HOLD.ON” is displayed, press the
NO
key to select the
<MEASURE> mode.
7.3.2 Span Calibration Using the Standard Solution Method
Note: To prepare standard solution, the following materials are required: approx. 2 to 3 liters of pure water, approx. 20 to 30 milliliters of
pH7 buffer solution, approx. 100 to 150 mg of NaCl, and commercially available sodium hypochlorite, or NaClO (the quantity of
which is so much that a free chlorine concentration of approx. 80% of the output range can be obtained by dilution).
Span calibration using the standard solution method is performed as follows.
Note: Before performing span calibration, confirm that the electrode does not remain open to the air as after zero calibration, and the
electrode rotates smoothly in the measuring tank.
Start span calibration at the point when zero calibration using the method described in Sec. 7.2.1 or
7.2.2 is finished and “SPAN” is displayed in the message display.
Note: When calibration is performed using the method in Sec. 7.2.1, the FC400G is in the MEAS mode (or <HOLD> mode) and “SPAN”
is not displayed. Refer to (2) of Sec. 5.4.1 and display “SPAN” in the <CAL> mode.
(1) Press the
YES
key to enter the span calibration mode.
Free chlorine concentration is displayed in the data display.
(2) Prepare standard solution.
First prepare a solution to dilute commercially available sodium hypochlorite solution. Prepare
a solution for dilution so that it consists of 10 milliliters of pH7 standard solution and 50 milliliters
of NaCl per one liter of pure water. Calibration requires 2 to 3 liters of dilution solution. Prepare a
standard solution by diluting the sodium hypochlorite solution using the dilution solution so that
the free chlorine concentration is approx. 80% of the output range.
Notes: • To prepare a standard solution, sample water may be used instead of dilution solution.
• To prepare a span calibration solution according to the official method, dilute the sodium hypochlorite using tap water so that the
free chlorine concentration is approx. 80% of the output range
(3) Supply the standard solution to the detector.
When the zero point has been calibrated using the open input circuit method, close the needle
valve at the sample water inlet of the detector and remove the sample water piping from the joint
of the measuring tank. Set the tubing and hardware so that sample water can be supplied at a
flow rate of at least 100 ml/min using a head difference or a pump and connect it to the detector
at the sample water inlet.
When zero point has been calibrated using the chlorine-free-water-based measurement method,
supply standard solution using the hardware used for the zero calibration.
(4) Measure the free chlorine concentration of the standard solution correctly using manual analysis
(e.g. an amperometric titration method). The exact free chlorine concentration of the standard
solution changes over time. Perform the operation in item (5) immediately after the manual
analysis is finished.
(5) Enter the obtained value in the data display and perform span calibration.
Confirm that the obtained value has been entered correctly and press the
ENT
key. This causes
the mg/L (or ppm) indication to blink during calibration operation. When the span calibration is
completed normally, “CAL.END” appears.
Note: If an error occurs during calibration operation, “END.E5” or “END.E7” is displayed in the message display. When this message is
displayed, take countermeasures, referring to Sec. 7.4.
(6) Reattach the tubing to the detector. Open the needle valve to allow the sample water to flow.
Adjust the aperture of the needle valve so that the sample water flows at the specified flow rate.