Teledyne LXT-280 - Manual (Page 31)

Dissolved Oxygen Transmitter Calibration
Teledyne Analytical Instruments 21
1. With an instrument magnet, activate the UP VERTICAL ▲
arrow key to reach the Contrast Menu.
2. Magnetically activate the RIGHT HORIZONTAL ► arrow key
to enter the calibrate mode. Observe the cursor move to the last
digit.
3. Using the HORIZONTAL ◄► arrow keys, position the cursor
under the digit to be adjusted. Increase or decrease the value by
magnetically activating the appropriate VERTICAL ▲/▼ arrow
key.
4. To save the contrast value and exit the calibrate mode,
magnetically activate the LEFT HORIZONTAL◄ arrow key
until the cursor is all the way to the left.
4.4 Zero Calibration
Because dissolved oxygen sensors experience minor variations in
membrane thickness, permeability, surface area and in the signal
conditioning amplifier from one sensor to the next, the zero point may
differ. In some cases, especially in low ppm measurements, a zero
calibration may be desirable.
Two zero calibrations are possible with a dissolved oxygen sensor:
1. Simulation of a zero oxygen environment
2. Using a true zero oxygen environment
The simulation of a zero oxygen environment is the easiest and can
be performed with good results; however, for extreme accuracy at the
low-end (near zero), the true oxygen environment is preferred. These
two calibration procedures are discussed in detail in the SP-1/SP-2
Sensor Manual. The following procedure describes the steps used to
calibrate a DO sensor to the LXT-280 instrument.
Procedure:
1. With an instrument magnet, activate the appropriate VERTICAL
▲/▼ arrow key to reach the Electrode Standardization Menu and
locate the cursor under the "1".
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.