Probe Calibration - Pentair POINT FOUR RIU3 Guía De Instalación Y Del Usuario

The calibration procedure will vary depending on the type of probe being used. In general, either 1-point or 2-point
calibrations can be done. Depending on the probe type, 1 or 2 –point calibrations may be recommended.
PV=(V_raw-Offset)×Slope
PV : Process variable – this is the value that is displayed on the main screen with the appropriate engineering units.
Vraw : Raw voltage input – this is the raw voltage value measured by the RIU3 from the probe.
Offset : The offset value is calculated by the RIU3 during calibration.
Slope: The slope value is calculated by the RIU3 during calibration.
To perform a typical 1-point calibration, the user places the probe in an environment with a known value for the
measured parameter. The user then enters the known value into the RIU3 and completes the calibration. The RIU3
will then calculate the Offset value so the PV matches the value that the user entered for the 1-point calibration.
To perform a typical 2-point calibration, the user places the probe in an environment with a known value for the
measured parameter. The user then enters the known value into the RIU3 and captures the first calibration point.
Next, the user places the probe in a different environment with a different known value for the measured parameter.
The user enters the know value into the RIU3 again and captures this value. The calibration then completes by
calculating both the Slope and the Offset so the PV matches user entered values with the captured raw voltage inputs.
The calibration procedure is slightly different for galvanic dissolved oxygen probes. Since these probes have a true
zero, the Offset is always zero. In this case, it is never necessary to complete a 2-point calibration. During a 1-point
calibration, the Offset will not be modified – it will remain at zero – and instead, the Slope will be calculated so the
PV matches the value the user entered for the 1-point calibration.
Calibrating Specific Probe Types
1) OxyGuard Commander Dissolved Oxygen (DO)/Temperature Probe
a. DO Calibration
With this probe type, the RIU3 will have 2 process variables corresponding to DO. The engineering units
for these PVs are %Sat (percent saturation) and mg/L. In order to calibration the DO, only the %Sat PV
must be calibrated. The mg/L PV will then be calculated based on the %Sat and the Temperature readings.
A 1-point calibration should be done with the %Sat PV since these probes have a true zero, meaning the
Offset will always be zero, and only the Slope needs to be calculated.
To complete a 1-point DO calibration for this probe, do the following:
i. Place the probe in air. Allow the probe readings to stabilize for 30 minutes.
ii. On the RIU3, press and hold the Return button for 3 seconds to enter the configuration menu.
iii. Using the Down button, scroll down to the Cal menu and click the Enter button.
iv. Scroll to "Oxy" and click the Enter button.
v. Scroll to "1-point" and click the Enter button.
vi. The current value of the %Sat PV will be displayed. You will want to change this to read 100 %Sat
since the probe is currently in the air. Use the Up and Down buttons and the Enter button to do this.
vii. Once you have entered 100 and clicked the Enter button once more, the RIU3 will attempt to capture
the calibration point and calculate the Slope. If the probe reading is stable and within reasonable limits,
the calibration point will be captured and a Cal OK message will be displayed.
viii. Use the Return button to return back to the main display. The %Sat PV should now read 100 %Sat.
ix. The probe can now be returned to use. You will have to allow another 30 minutes for the probe
temperature to stabilize. After this, the probe will now be reading accurately.
POINT FOUR™ RIU3™ Remote Monitor/Controller Installation and User's

PROBE CALIBRATION

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Guide