Teledyne LXT-220 - Manual (Page 49)

Dissolved Oxygen Controller Operation
Teledyne Analytical Instruments 49
2 DO 10.0 ppm
Cal -157.5 mV/FS
Standardization menu @ factory default
settings
1 DO .00 ppm
Cal .0 mV
Standardization menu DO @ factory default
settings
4. Immediately before making the calibration adjustment, note the
current value on the display and add the differential to the
current value. This "total adjusted" value is entered as the buffer
value.
3.4.2.5 C ALIBRATION E RROR D ETECTION & E LECTRODE O PERATIONAL
G UIDELINES
If the slope calibration performed in Section 3.4.2.3 is not within
the predetermined limits of the instrument, a flashing asterisk (*) will
appear.
The presence of the asterisk indicates a potential calibration
problem. In general, if the asterisk appears, the integrity of the
electrode, the buffer solutions or the handling procedure should be
questioned. See the dissolved oxygen sensor manual for specifics on the
electrode.
3.4.2.6 B ACK - TO -F ACTORY C ALIBRATION
This feature allows the LXT-220 to be reset to "typical electrode"
for electrode potentials. As the electrode ages it will deteriorate and the
mV/FS will decay and will eventually require replacement. If the
membrane is torn or coated the calibration will be either sluggish or out
of range.
The following procedure for returning the LXT-220 to factory
calibration can be used for both standardize and span calibrations.
Procedure at the Standardization Menu:
1. Position the cursor under the "C" in "Cal."
2. Press both horizontal CALIBRATE keys simultaneously and
observe the cursor briefly move to the right. The default setting
is complete.