Single and dual input analyzers for pH/Redox (ORP)
AX416, AX436, AX460, AX466 & AX468 7 Calibration
56 IM/AX4PH Rev. P
7 Calibration
7.1 Equipment Required
1. Millivolt source (pH or Redox input simulator): –1000 to 1000 mV.
2. Decade resistance box (Pt100/Pt1000 temperature input simulator): 0 to 10 k (in increments of 0.01 ), accuracy ±0.1 %.
3. Digital milliammeter (current output measurement): 0 to 20 mA.
7.2 Preparation
1. Switch off the supply and disconnect the conductivity cell(s), temperature compensator(s) and current output(s) from the
analyzer's terminal blocks.
2. Sensor A – Fig. 7.1:
a. Link terminals B9 and B10.
b. Connect the millivolt source to terminals B14 (–ve) and B16 (+ve) to simulate the pH or Redox input. Connect the millivolt
source earth to the Case Earth (Ground) Stud – see
Fig. 6.8
(wall-/pipe-mount analyzer) or
Fig. 6.10
(panel-mount analyzer).
c. Connect the 0 to 10 k decade resistance box to terminals B9 and B11 to simulate the Pt100/Pt1000/Balco 3K.
Sensor B (dual input analyzers only) – Fig. 7.1:
a. Link terminals B1 and B2.
b. Connect the millivolt source to terminals B6 (–ve) and B8 (+ve) to simulate the pH or Redox input. Connect the millivolt source
earth to the Case Earth (Ground) Stud – see
Fig. 6.8
or (wall-/pipe-mount analyzer) or
Fig. 6.10
(panel-mount analyzer).
c. Connect the 0 to 10 k decade resistance box to terminals B1 and B3 to simulate the Pt100/Pt1000/Balco 3K.
3. Connect the milliammeter to the analog output terminals.
4. Switch on the supply and allow ten minutes for the circuits to stabilize.
5. Select the
FACTORY SETTINGS page and carry out Section 7.3.
Note.
The analyzer is calibrated by the Company prior to dispatch and the Factory Settings pages are protected by an access
code.
Routine recalibration is not necessary – high stability components are used in the analyzer's input circuitry and, once
calibrated, the Analog-to-Digital converter chip self-compensates for zero and span drift. It is therefore unlikely that the
calibration will change over time.
Do Not attempt recalibration without first contacting ABB.
Do Not attempt recalibration unless the input board has been replaced or the Factory Calibration tampered with.
Prior to attempting recalibration, test the analyzer's accuracy using suitably calibrated test equipment – see Section 7.1,
page 56 and see Section 7.2, page 56.
Note. Resistance boxes have an inherent residual resistance that may range from a few m up to 1 . This value must be taken
into account when simulating input levels, as should the overall tolerance of the resistors within the boxes.
Fig. 7.1 Analyzer Terminal Links and Decade Resistance Box Connections
Terminal link
pH/Redox
Input Simulator
Temperature
Simulator
B10
B11
B12
B13
B14
B9
Sensor A Terminal Numbers
Sensor B Terminal Numbers
B2
B3
B4
B5
B6
B1
B15
B16
B7
B8
ve
+ve
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