Teledyne LXT-280 - Manual (Page 25)

Dissolved Oxygen Transmitter Operation
Teledyne Analytical Instruments 15
Effective Range = (500 mVa/275 mVa) x (10 ppm)
Effective range = (1.818) x (10 ppm)
Effective range = 18.18 ppm
A reading higher than 18.18 ppm is not meaningful under the
circumstances given in the above example. At 18.18 ppm, the millivolt
input from the sensor is greater than 500 mV and saturates the
transmitter input circuitry.
The bottom line of the Electrode Data Screen displays the electrode
zero offset from the last zero calibration. This value is the dissolved
oxygen value at which the electrode output is zero millivolts. Because
the Electrode Data Screen indicates the deviation from zero, the
information is helpful in determining the quality of the dissolved
oxygen electrode. In conjunction with regular calibrations, the
Electrode Data Screen can provide valuable information to track
electrode service.
3.2.4 Electrode Zero Menu
This menu provides the means with which to perform the zero
calibration for the Dissolved Oxygen electrode. The screen shown below
shows the Electrode Zero Menu for Dissolved Oxygen in percent
oxygen or ppm oxygen.
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 calibration point.
Calibration procedures are described in Section 4.
2 DO 100.0
Cal -400.0
ElectrodeSpsn Menu, %
2 DO .0
Cal -400.0
Electrode Span Menu, ppm