LaMotte DHA 3000 Digital pH Meter - Manual (Page 3)

GENERAL INFORMATION
The DHA-3000 pH meter consists of three major components: the pH
electrode, the temperature probe and the meter.
The pH electrode consists of a glass, hydrogen-ion selective electrode, and
a reference electrode, combined into a single unit. The glass electrode is
specially treated to measure only hydrogen ions, while the reference
electrode is silver surrounded by silver chloride, and it provides a “zero” or
reference point for the measurement. This “zero” point means any change
in potential measured at the glass electrode is attributed to hydrogen ions,
and therefore expressed as pH.
The temperature probe serves a dual purpose, and may be connected to
the pH electrode. When the temperature probe is in the sample at the
same time as the pH electrode, it measures the temperature and allows the
meter to automatically compensate the temperature to 25°C. Secondly, it
allows the user to measure the actual temperature of the sample in °C.
When the temperature probe and pH electrode are immersed in the
sample, the meter measures the difference in potential between the glass
electrode and the reference electrode. This electronic measurement is
converted from millivolts to pH units, and the result appears on the
display.
If, for some reason, the temperature probe can not be used during the pH
measurement, the meter must be manually compensated for temperature.
To do this standardize the meter with buffers which are the same
temperature as the sample, and use the “Slope” knob to standardize meter
to the proper pH.
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