Extech Instruments 341350A User Manual page 7

pH Troubleshooting Chart
Symptom Cause
Long response Clogged Junction
time or reading
drift
Oil, paint, dyes, suspended solids
on sensor
Dry Bulb Long term storage without wetting Soak electrode tip in wetting cap filled
Static Charge Wiping electrodes
Same readings Cracked or broken bulb
in different
buffers and
samples
Erratic LCD Samples have low ionic strength
display (lacks salt); e.g. distilled, de-
ionized, boiled, lake water (high
pressure)
Notes on pH measurements and electrodes
1. The Electrode should be stored in its wetting cap until used. Use a pH 4 buffer solution
or tap water as the storage medium.
2. If bubbles are seen in the bulb area, hold the electrode by its cap and shake
downwards until bubbles are removed.
3. To improve speed of response, vigorously stir the electrode in the sample, buffer, or
rinse solution.
4. After exposure to a sample, buffer, or rinse solution, shake the electrode with a snap
motion to remove residual drops of solution.
5. When possible, use part of the next sample/buffer to be measured as a rinse solution,.
6. Keep buffers and samples at the same temperature to avoid temperature effects.
7. pH readings stabilize faster in some solutions than others; allow time to stabilize.
8. Electrodes deteriorate over time. If accuracy falls to 10% the electrode should be
cleaned. If no improvement is observed, replace the electrode.
Notes on the Conductivity/TDS/Salt Cell
1. Cell Storage: On sheathed cells, replace the sheath over the cell when storing. For
non-sheathed versions, soak the cell tip in de-ionized water for storage.
2. Cell Cleaning: After each use, the cell tip should be rinsed with de-ionized water. If
solids build up inside the cell carefully remove with a cotton swab soaked in solvent
taking care not to touch the metal parts of the inner cell.
Recommended Solution
Soak in 4.07 M KCL @ 60
minutes
Rinse electrode alternately with
materials solvent then buffer 7.00
with 1ml 7.00 buffer for 24 to 48 hours
Rinse electrode in 7.0 buffer and blot.
Do no wipe electrode.
Replace electrode. Use bulb guard.
Avoid plunging electrode to bottom of
container and spinning bars. A
wetting cap will protect bulb between
measurements.
For each 50 ml of sample add 1 drop
(50uL) of SAT.KCL No alteration in
pH will occur by inert KCL.
341350A V1.1 1/09
7
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