Yokogawa SPS24 - Manual (Page 20)

<3. Sensor Management>
3-3
IM 12A01S02-01E 1st Edition : May 10, 2013-00
3.3 [Start calibration]
Clicking on [Start calibration] in “Current measurement readings” will display the selection screen
that shows sensors to be calibrated.
Sensors of the same model and type can be calibrated simultaneously.
When a sensor is selected, the upper part of the sensor button turns blue for identification.
Before pH measurement, calibrate the pH sensor with the standard solution.
Before ORP measurement, check the electrode as regular maintenance.
Calibration object are pH, ORP, rH, and temperature. pH calibration has manual and automatic
modes, each with three calibration types.
n pH Calibration (Manual)
The unit is adjusted to match the value of the buffer standards or a process solution with a known
pH value (buffer solution).
The user determines the pH value, temperature influence, and stability.
Select the calibration type from among [Zero/slope], [Zero/slope/ITP(3point)], and [Zero/slope1,2
(3point)].
Calibration is performed stepwise; follow the prompts displayed on the screen.
A stability check is conducted at each measurement point. Proceed to the next step only after the
reading has stabilized.
At calibration, we advise leaving the sensors for three to five minutes in the buffer solution before
proceeding to the next step even when the reading has stabilized. This will give reliable and
accurate calibration results.
l Zero/slope
This calibration type is one-point or two-point calibration.
One-point calibration performs the zero adjustment only. Two-point calibration performs the zero
and slope adjustments.
l Zero/slope/ITP(3point)
This calibration type is ITP-type three-point calibration.
If ITP does not have pH 7, three-point calibration is performed to obtain the zero (asymmetry),
slope (sensitivity), and ITP (isothermal point) for calibration.
Limitations
• Three different buffer solutions whose difference in pH value between buffer solutions is 1
pH or more should be used.
(1st buffer < 2nd buffer < 3rd buffer or 1st buffer > 2nd buffer > 3rd buffer)
• The 2nd buffer solution should be pH 7 ± 2.
• The temperature difference between the 1st and 3rd buffer solutions should be 20ºC or
more.
• The temperature difference between the 2nd and 3rd buffer solutions should be 20ºC or
more.