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Model LXT-230 Instruction Manual / 14
2 pH 4.00
-58.2 mV/pH
2 ORP 180.0 mV
.980 mV/ORP
Procedure:
1. Press the appropriate MENU SELECTION key to reach the Electrode Standardization
Menu and locate the cursor under the "1" as illustrated in section 3.2.4.
2. For diagnostic reasons note the pH and mV values from the prior calibration.
3. Clean the electrode and insert the sensor into the desired buffer.
4. Press both horizontal CALIBRATE keys simultaneously to enter the calibrate mode.
Observe the diagnostic value on the bottom line change from historical data to a
real-time value and that the term "CAL" has disappeared.
5. To change the buffer point, position the cursor under the desired digit using the left-
hand CALIBRATE key.
6. Increase or decrease the value by pressing the appropriate vertical CALIBRATE key.
7. Wait for the real-time mV value to stabilize.
8. To file the calibration and exit the calibrate mode, press either MENU SELECTION
key.
6.4 Two-Point Buffer Calibration (Span)
When first installing an electrode, a two-point buffer calibration should be used to
compensate for electrode slope variations or efficiency.
Procedure:
1. Perform a one-point calibration as outlined in section 5.3.
2. Press the appropriate MENU SELECTION key to reach the Electrode Span Menu and
locate the cursor under the "2" as illustrated in section 3.2.5.
3. For diagnostic reasons note the pH and mV values from the prior calibration.
4. Press both horizontal CALIBRATE keys simultaneously to enter the calibrate mode.
Observe the diagnostic value on the bottom line becomes a real-time value and that
the term "CAL" has disappeared.
5. To change the buffer point, position the cursor under the desired digit using the left-
hand CALIBRATE key.
6. Increase or decrease the value by pressing the appropriate vertical CALIBRATE key.
7. Wait for the real-time mV value to stabilize.
8. To file the calibration and exit the calibrate mode, press either MENU SELECTION
key.
A perfect electrode slope (efficiency) is -59.1 mV/pH and ORP is 1mV/mV. If the value falls
below -50.0 mV/pH or ORP .9 mV/mV, the electrode should be serviced or replaced.
IMPORTANT
If a flashing asterisk appears during or after calibration, the electrode may require service,
or the buffer solution may be contaminated. Refer to section 5.6 for details.
NOTE:
Comparing the millivolt values before and after the calibration provides a valuable
1 pH 7.00
-3.2 mV@25
1 ORP .0 mV
85.9 mVa