Campbell Scientific CSIM11 pH and ORP Sensors - Manual (Page 21)

CSIM11 pH and ORP Probes
• Coatings can cause 1) Slower Response; 2) Zero Offset increase;
3) Dehydration
• Steam Sterilization causes 1) Dehydration; 2) Ag/AgCl dissolving from
Silver Reference Element
9.1 Replacing Reference Electrolyte
Readings that drift indicate the electrolyte should be checked.
Refill Procedure:
1. Clean the probe tip as discussed in the maintenance procedures below.
2. Remove the reference reservoir plug. Place it where it will stay clean.
3. Rinse the reservoir with deionized water repeatedly to remove the old
solution. Drain out all remaining water.
4. Completely fill the reservoir with the new reference solution. It does not
take very much. Make sure you keep the bottle tip clean, and replace the
bottle cap immediately after using the bottle.
The bottle of refill solution contains undissolved salts; this is to
ensure the solution remains saturated.
5. Replace the red plug applying new pipe tape. Make sure the plug is
screwed back in as far as it was originally.
Because the new reference solution is viscous, you may need to wait a few
minutes while the reference solution settles. If necessary, take the probe in
hand and gently swing it in a downward arc to speed the flow of solution and
remove air pockets. Add more solution as needed to completely fill the
reservoir.
9.2 Electrode Cleaning
pH and ORP sensors require more maintenance than many other types of
sensors. The ORP platinum band can foul with algae and other biological
sources. Cleaning will be required approximately every 1 to 2 weeks. Fouling
can be minimized by locating the probe in a very dark place.
Slow response and large offsets may indicate the measurement electrode has
become coated. The nature of the coating will dictate the type of cleaning
technique that should be used.
Soft coatings, like foodstuffs or bacterial films are best removed using a squirt
bottle or the water jet from a faucet. If this is not successful, then wiping with
a soft wet cloth is the best choice.
Hard coatings, like calcium or lime scale are best removed with a solvent
appropriate for the particular coating. A 5 percent solution of HCl would be a
good choice for the calcium scale. If unsure of the proper solvent to remove a
hard mineral coating, alternate between 5 percent HCI and 4 percent NaOH for
NOTE
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