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1. ON/OFF (POWER) key: The ON/OFF (POWER) key toggles the power
of the instrument on and off. The current mode and pH/ion calibration
values are saved to the internal non-volatile memory of the instrument
when turned off and restored when turned back on.
2. MODE key: The MODE key selects the display mode of the instrument.
Pressing the MODE key cycles the display sequentially from pH, mV and
ion. THe calibration values are not affected by changing the display modes.
3. STAND/STAND I, SLOPE/STAND II key: The STAND/STAND I and
SLOPE/STAND II keys are for standardizing the instrument only.
4. UP and DOWN key: These keys are used to manually enter the
temperature values. The UP key increments the temperature, while the
DOWN key decrements the temperature. These keys will not respond
when operating in the automatic temperature compensation (ATC) mode.
5. RESOL. key: The RESOL. key toggles the resolution of the instrument
in pH or mV mode. But not for ion mode.
6. CLEAR key: The CLEAR key is used to reset the instruments mode and
clear the pH/ion calibration values. The CLEAR key has a delayed
reaction of 2 seconds before responding to protect from accidential key
presses. However, When the instrument display an error the CLEAR key is
pressed, all the LCD segments and annuciators will be on for a 2~3
seconds and the instrument will enter into the pH mode. The CLEAR key
is intended to be used only when errors are made that require the
instrument to be recalibrated.
MEASUREMENT ERROR INDICATIONS
Er1 1. pH electrode offset greater than +/- 1.5 pH range
2. Buffer 7.00pH (model 6250/6219), 6.86pH (model 6250C/6219C)
not correct
Er2 1. pH electrode slope off by more than +/- 30 % of ideal slope
2. Buffer 4.00pH, 9.18pH (model 6250C/6219C), 10.01pH (model
6250/6219) not correct
Er3 Temperature out of the -5.0 to 125.0 degree C range
Er4 Buffer temperature out of the 0 to 50.0 degree C range
Er5 1. pH values out of the -2.000 to 16.000 pH range when in pH mode
2. mV values out of the -1999.9 to 1999.9 mV range when in mV
