LTH Electronics MTD75, Operation Manual

Page: 137 / 266

pH Calibration
MTD75 Operation Guide - 135 -
pH Cali
bration
Manual pH Sensor Calibration
When using Manual calibration mode it is possible to do either a single or two point calibration. This is
accomplished by using the
Buffer and Slope menu items. However it is important to do the calibration
in the correct order:
1. Adjustment of the Buffer (Offset) value at 7.00 pH.
2. Adjustment of the Slope (Gain) value at any other pH (usually 4 or 9 pH).
If a single point calibration is required then only the buffer should be adjusted and no adjustment
made to the slope.
As actual pH buffer values are used no compensation is made for the buffer solution with temperature
in the instrument. It is important therefore to know the actual buffer value at the temperature of the
solution. The standard LTH 4, 7 and 9 pH values at temperature can be seen on page 137.
It is also important that the buffer temperature is entered into the Calibration Manual Temperature
Input if manual temperature compensation is being employed. Alternatively any automatic
temperature compensation element should be placed in the buffer solution with the pH sensor if Auto
TC is being used.
Calibration Principle
The default method of calibration is “Manual” mode,
however if the probe is pH and the type is glass then
“Auto” mode may have been selected. If this is the
case then calibration principle will need to be set to
manual.

/

– Select Option
EXIT – Cancel
– Save Selection
pH Buffer (Offset) Calibration
The pH buffer calibration enables the user to adjust
the sensor buffer until the displayed reading matches
the known input. To activate the function select “pH
Buffer (Offset) Cal” and press enter.
The current sensor reading can be seen in the pop-up
window and is adjusted by pressing the up and down
arrows. When the reading is correct press the enter
button to store the calibration.
It is recommended that the buffer should be adjusted
at 7pH (
±
2pH) for a glass probe, and 0pH (+2pH) for
an antimony probe.
Note. If the electrode is new, pressing the “new”
button will reset the existing offset and slope and
add a “new electrode” entry in the calibration history.

/

– Adjust the Reading Up or Down
NEW – Register New Electrode
EXIT – Cancel
– Save Calibration