Reply To: Inexpensive DO probe recommendations

The cathode is exposed. I did rinse the cathode when I cleaned everything and there was nothing obviously fouling it. The probe tip being under the membrane cap I considered pretty well protected. After examining my data and pictures of the probe tip, Atlas Scientific had no explanation other than saying maybe there was an unknown material inside the probe suppressing the chemical reaction. (they declined doing a failure analysis). Your suggestion is interesting. Although I wouldn’t think the probe is old enough for a typical tarnish maybe something has been coating it since the beginning. Oil, glue, plastic off gassing, all long shots but I have nothing to lose. I’ll try a bit sanding and see if something changes. Thanks.