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Model LXT-230 Instruction Manual / 8
3.2.2 Main Menu
This menu appears after the Copyright Display when power is first applied to the LXT-230.
The Main Menu displays the measured process variable, temperature, and the current
output in percent of full-scale. While in this menu, the current output can be adjusted and
locked in a manual mode to provide an undisturbed output during buffer calibrations.
3.2.3 Electrode Diagnostic Screen
As an informational screen only, this display provides diagnostic data pertaining to the
electrode. The top line displays the real-time (active) absolute millivolt value (mVa) the
electrode is generating, not compensated for temperature variations. The bottom line
displays the electrode isopotential from the last calibration. The isopotential (electrode
offset) is the value at which the electrode output is zero millivolts. A perfect pH electrode
will indicate an isopotential of 7.00 pH. Replace the electrode if the isopotential is less than
6.00 pH or greater than 8.00 pH.
A perfect ORP electrode will indicate an isopotential of 86 mV @ 25°C. Replace the electrode
if the isopotential is less than 36 mV or greater than 136 mV @ 25°C.
This information is extremely helpful in determining the diagnostic status of a pH or ORP
electrode. In conjunction with regular calibrations, the Electrode Diagnostic Screen provides
valuable information to track electrode performance.
3.2.4 Electrode Standardization Menu
Provides the means with which to perform a one-point calibration (standardization) or the
first point of a two-point calibration. For pH this point is typically 7.00 pH and ORP this point
is typically 0.00 mV.
Before entering the calibrate mode, the menu provides historical data from the last
calibration. The top line displays the buffer, or calibration point, at which the last calibration
was performed. The bottom line displays the temperature compensated mV value the
electrode generated at the buffer point. Please note that temperature compensation is not
performed for ORP. When in the calibrate mode, the bottom line displays the real-time, or
active, millivolt value.
3.2.5 Electrode Span Menu
Provides the means to perform the span calibration, or the second point of a two-point
calibration. Before entering the calibrate mode, the menu provides historical data from the
last calibration.
pH 7.00
_50.0% 25.0°C
ORP -500.0 mV
_25.0% 25.0°C
Input .0 mVa
0 mVa 7.00
Input -500.0 mVa
0 mVa .0 mVa
1 pH 7.00
Cal .0 mV/pH
1 ORP .0 mV
Cal .0 mVa
2 pH .00
Cal -59.1 mV/pH
2 ORP .0 mV
Cal 1.000 mV / ORP