MODEL SOLU COMP II | SECTION 6.0 |
| CALIBRATION |
6.5 STANDARDIZATION — pH
6.5.1 Purpose
1.The pH measured by the Solu Comp II analyzer can be changed to match the reading from a second or ref- eree instrument. The process of making the two readings agree is called standardization.
2.During standardization, the difference between the two pH values is converted to the equivalent voltage. The voltage, called the reference offset, is added to all subsequent measured cell voltages before they are con- verted to pH. If a standardized sensor is placed in a buffer solution, the measured pH will differ from the buffer pH by an amount equivalent to the standardization offset.
6.5.2 Procedure
1.Install the sensor in the process liquid.
2.Once readings are stable, measure the pH of the liquid using a referee instrument.
3.Because the pH of the process liquid may change if the temperature changes, measure the pH of the grab sample immediately after taking it.
4.For poorly buffered samples, it is best to determine the pH of a continuously flowing sample from a point as close as possible to the sensor.
5.Standardize the Solu Comp II analyzer by following the steps below.
CalibrateHold
ProgramDisplay
Calibrate?
Sensor1Sensor2
CalSensor1?
Measurement Temp
S1 | Standardize |
Slope | BufferCal |
|
|
|
|
Live | 7.00pH |
CalS1 | 07.00pH |
|
|
|
|
Invalid | Input! |
Max: | 14.00pH |
|
|
|
|
S1 | Standardize |
Slope | BufferCal |
|
|
a.Press MENU. The main menu screen appears. Choose Calibrate.
b.Choose Sensor1 (pH sensor).
c.Choose Measurement.
d.Choose Standardize.
e.The top line shows the present pH reading. Change the pH reading in the second line to match the referee instrument. Press ENTER.
f.The screen at left appears if the entered pH was greater than 14.00. The display then returns to step e. Repeat the standardization.
g.If the entry was accepted, the screen at left appears. To verify that the new pH was accepted, return to the main display by pressing MENU fol- lowed by EXIT.
52
