Teledyne LXT-280 - Manual (Page 26)

Operation LXT-280
Teledyne Analytical Instruments 16
3.2.5 Electrode Span Menu
From this menu, you can perform the span calibration for the
dissolved oxygen electrode. Before entering the calibrate mode, the
menu provides historical data from the last calibration.
The top line displays the calibration point at which the last
calibration was performed. For DO transmitters, the bottom line displays
the electrode slope, or efficiency, in millivolts at full scale. When in the
calibrate mode, the bottom line displays the real-time, or active,
millivolt value.
3.2.6 Output Calibration Menu
On the next menu, the current output ranges are displayed and can
be adjusted in this menu.
The 4 mA and 20 mA points may be defined in percent dissolved
oxygen or parts per million dissolved oxygen, depending on the software
installed in the transmitter. The maximum allowable ranges are 0 to
200% and 0 to 20 ppm.
3.2.7 DO Locus
The DO Locus Menu defines the point at which a family of
dissolved oxygen concentration curves intersect for a specific sensor or
electrode. The locus is derived by plotting the sensor output versus
temperature at different dissolved oxygen concentrations. Empirical
data for Teledyne sensors defines the locus to be approximately -17°C.
Because dissolved oxygen sensors have different temperature slopes at
2 DO 100.0
Cal -400.0
Output Calibration Menu, %
2 DO .0
Cal -400.0
Output Calibration Menu, ppm
4 mA .0
20 mA 200.0
Output Calibration Menu, %
4 mA .0
20 mA 20.0
Output Calibration Menu, ppm