OPTIONAL PH SENSOR MAINTANCE
The sensor, like the instrument, is constructed of durable, corrosion resistance materials, See Figure 6. It is designed to
withstand rough use in laboratories, industrial installations, or waste treatment systems. The sensor may be used in any
water solution, but will be attacked by organic solvents such as chloroform, benzene, or ethyl acetate, Special sensors
are available for use with such materials, and for temperature extremes. Consult the factory for details.
The only service required on the sensor is keeping the measuring glass clean.
HELPFUL OPERATING TECHNIQUES
As shipped, the electrode tip is covered by a protective cap which serves both to keep the reference from drying
and to prevent breakage. This cap is a snug fit and it contains a pressure relief hole to facilitate removal and
installation. As supplied, this hole is covered by a piece of vinyl tape to retain moisture inside the cap. Before
removing or reinstalling cap, the tape must be removed to expose the pressure relief hole.
During shipment the air pocket in the electrode's stem may move into the bulb area. If bubbles are seen in the
bulb area, hold the electrode by its top cap and shake downwards as is done with a clinical thermometer.
Vigorously stir the electrode in the sample, buffer or rinse solution. This action will bring solution to the electrode's
surface more quickly and improve speed of response.
After exposure to a sample, buffer or rinse solution, shake the electrode with a snap motion to remove residual
drops of solution. This action will minimize contamination from carryover.
As a rinse solution, use a part of the next sample or buffer which is to be measured. This action also will minimize
contamination from carryover.
When calibrating, use a buffer close in value to that expected from the sample. This action will minimize any span
Keep buffers and samples at the same temperature. This action will eliminate the need to correct values for
temperature effects 8. pH readings stabilize faster in some solutions than others; allow time for the reading to
stabilize. In general, buffers provide stable readings in several seconds (tris buffers take somewhat longer) while
samples usually take longer times.
Keep in mind that all pH electrodes "age" with time. Aging is characterized by shortened span and slower speed of
response. If pH meter has a "slope" (span) control, the calibrate control can be adjusted to compensate for
electrode span errors (but will not