Probably nothing of interest here to old hands but newer rb divers may get something out of it. Nevertheless, a real time example of the death of a cell, re-iterating the need to regularly current limit check cells and replace within recommended timescales. This cell was less than 19 months old from date of manufacture, had shown very little variation during linearity checks and always reacted quickly to pressure changes. Cells 2 and 3 had recently been changed.
Date Linearity check Lim check
13/2/13 10.8/50mV 1.6
26/3/13 10.8/50 1.6
17/4/13 10.4/49.2 1.7
25/4/13 10.6/49.7 1.6
11/5/13 10.6/49.7 1.6
20/5/13 10.6/50 1.6
30/5/13 10.6/49.5 (last time calibrated) 1.6
23/6/13 Dive 1 in shallow lake, cell showing signs of slightly lagging other two but could maintain set point of 1.3 , but dropped set point to 1.0 as a precaution. Dil flush lowered all readings as expected but cell 1 remained slightly lower. Dive 2 kept to shallow check dive, blasted 02 at it at 6m, limited to 1.35 and voted out by other two cells.
The conclusion here for this cell is that even though it has performed faultlessly for its life in the unit, it failed relatively pretty quickly even though the session before today gave the expected reading. Regular monitoring showed the only indication that something was changing when it became clear that cell 1 was starting to lag the other two by a set point reading regularly of 0.02 less during the dive, which was unusual behaviour compared to how it had performed. It couldhave been somethng else causing the lag, but in this case I suspected it was due to becoming limited. No new lessons learnt, just a reminder to remain familiar with cell behaviour, query any variation and test regularly.