OK, question for the group. I don’t have the head with me, so I don’t have the raw data download to post, but here is the general issue.
JJ CCR, three cells from the same batch, dated March, 2019
Typically when I build the unit and turn on the controller with the head exposed to air, I get something like this for mV output of cells 1, 2 and 3:
10.6, 10.6, 9.6
I calibrate with 100% O2, and while cell number 3 seems to read a bit higher during the dive (“waking up”?), it stays within acceptable range, so no issues.
Last week, I got 10.6, 10.6, 9.0. on the build. Still within acceptable range. I calibrated with 100% O2, no problem. mV on calibration was 47.4, 47.5 and 40.7 (all a bit below linear, but not too far off).
During the dive, cell 3 started reading fairly high PO2 (something like 1.3, 1.3, 1.47). I didn’t get a great dil flush, so I thumbed the dive. I figured that the third cell had woken up and started delivering voltage more in line with the other two, so the calibration earlier was giving me a high reading.
On the boat I pulled the head and let it dry a bit. Then I reassembled it - now all three cells were reading around the same in air (10.6). Calibrated with 100% O2, all good, and went for a dive - no issues, all three cells held set point well and very close to each other.
So my question is, should I replace cell #3, or change my build procedure to try to get it to wake up before doing the pre-dive calibration? I was thinking about exposing it to 100% O2 for a bit with the head open, and then waiting to see if the mV in air rises to the same general range as #1 and #2, and then doing the calibration after that.
I have a mini-check from Narked at 90, so when I get back to where the rebreather is I could also check linearity at higher PO2, wasn’t able to do that after last weekend…
JJ CCR, three cells from the same batch, dated March, 2019
Typically when I build the unit and turn on the controller with the head exposed to air, I get something like this for mV output of cells 1, 2 and 3:
10.6, 10.6, 9.6
I calibrate with 100% O2, and while cell number 3 seems to read a bit higher during the dive (“waking up”?), it stays within acceptable range, so no issues.
Last week, I got 10.6, 10.6, 9.0. on the build. Still within acceptable range. I calibrated with 100% O2, no problem. mV on calibration was 47.4, 47.5 and 40.7 (all a bit below linear, but not too far off).
During the dive, cell 3 started reading fairly high PO2 (something like 1.3, 1.3, 1.47). I didn’t get a great dil flush, so I thumbed the dive. I figured that the third cell had woken up and started delivering voltage more in line with the other two, so the calibration earlier was giving me a high reading.
On the boat I pulled the head and let it dry a bit. Then I reassembled it - now all three cells were reading around the same in air (10.6). Calibrated with 100% O2, all good, and went for a dive - no issues, all three cells held set point well and very close to each other.
So my question is, should I replace cell #3, or change my build procedure to try to get it to wake up before doing the pre-dive calibration? I was thinking about exposing it to 100% O2 for a bit with the head open, and then waiting to see if the mV in air rises to the same general range as #1 and #2, and then doing the calibration after that.
I have a mini-check from Narked at 90, so when I get back to where the rebreather is I could also check linearity at higher PO2, wasn’t able to do that after last weekend…