Extech Instruments 793950343524 User Manual page 7

1.800.561.8187
pH Troubleshooting Chart
Symptom
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 in Cracked or broken bulb
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 a
4.0 M KCL solution.
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.
www.
Cause 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.
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