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STORAGE
1. It is recommended that electrodes be stored in their
original shipping containers until needed.
2. Do not store at temperatures below -5°C (23°F).
3. Electrodes should be stored with a protective cap
containing KCl solution (PN 9210342).
4. For overnight storage, immerse the sensor in tap
water or 4 pH buffer solution.
5. A pH glass electrode does have a limited shelf life
of one year.
ELECTRODE PREPARATION
1. Remove electrode from shipping container.
2. Remove the protective boot covering the electrode
bulb.
3. For pH electrode, rinse away salt film with clean
water, then shake the electrode so that the internal
solution fills the bulb, thus removing any air trapped
there.
INSTALLATION
For sensor dimensions, see Figure 1.
For sensor orientation, see Figures 2 and 3.
For wiring, see Figures 4 - 18.
TWO POINT BUFFER CALIBRATION
Select two stable buffer solutions, preferably pH 4.0
and 10.0 (pH buffers other than pH 4.0 and pH 10.0
can be used as long as the pH values are at least two
pH units apart).
NOTE
A pH 7 buffer solution reads a mV value of
approx. zero, and pH buffers read approximately
± 59.1 mV for each pH unit above or below pH 7.
Check the pH buffer manufacturer specifications
for millivolt values at various temperatures since
it may affect the actual value of the buffer solution
mV/pH value.
1. Immerse sensor in the first buffer solution. Allow
sensor to equilibrate to the buffer temperature (to
avoid errors due to temperature differences
between the buffer solution and sensor tempera-
ture) and wait for reading to stabilize. Value of buffer
can now be acknowledged by analyzer/transmitter.
2. Once the first buffer has been acknowledged by the
analyzer/transmitter, rinse the buffer solution off of
the sensor with distilled or deionized water.
3. Repeat steps 1 & 2 using the second buffer solution.
4. The theoretical slope value, according to the Nernst
equation for calculating pH, is approximately 59.17
mV/pH. Over time the sensor will age, both in the
process and in storage, and will result in reduced
slope values. To ensure accurate readings, it is rec-
ommended that the electrode be replaced when the
slope value falls below 47 to 49 mV/pH.
RECOMMENDED pH SENSOR
STANDARDIZATION
For maximum accuracy, the sensor can be standard-
ized on-line or with a process grab sample after a
buffer calibration has been performed and the sensor
has been conditioned to the process. Standardization
accounts for the sensor junction potential and other
interferences. Standardization will not change the sen-
sor’s slope but will simply adjust the analyzer’s reading
to match that of the known process pH.
MAINTENANCE FOR pH ELECTRODE
Electrodes should respond rapidly. Sluggishness, off-
sets, and erratic readings are indicators that the elec-
trodes may need cleaning or replacement.
1. To remove oil deposit, clean the electrode with a
mild non-abrasive detergent.
2. To remove scale deposits, soak electrodes for 30 to
60 minutes in a 5% hydrochloric acid solution.
3. Temperature effect on life expectancy: If glass elec-
trode life expectancy is 100% @ 25°C (77°F), then
it will be approximately 25% @ 80°C (176°F).
2
CAUTION
The buffer in the protective boot may cause skin or
eye irritation.