Quote: (Originally Posted by
jradomski)
I have been testing a batch of AI cells for a few months now.. They seem to be performing well.. I am glad I had a second look... I tried them a few years ago and didn;t get as good results..
AI has a wide variety of cells, some have minor voltage differences so you can match them up better for your electronics.. for example
the r22d substitute psr-11-39-md is not a good choice for the HH since the guaranteed voltage is only 8.5mv, while the psr-11-39-mhd is a good choice (contrary to their website) since the guaranteed voltage is 9.0 mv
Quote: (Originally Posted by
paulraymaekers)
same experience here, we will ship the rEvo II with AI cells psr-11-39-rEvo: a bit more expencive, but minimum 9.5 mV, so w're shure the rEvodreams always work, even after some time!
regards
paul
OK so I have been thinking about this low/high mV-test that several PO2-systems include.
I'm not convinced that a cell reading a higher mV is always a better cell and that a slightly low mV really gives any sign that a cell is bad. Ofcourse if the mV is way high or very low the cell is failing.
But is buying cells with a higher guaranteed minimum mV really making the cells more reliable? Or is it just a 'trick' to help pass the mV-test of certain units?
If its just a trick to make it pass the test, then why are the systems designed the way they are?
I understand that a low mV output can be problematic for the amplifier? But is that all of the reason? And if so, why not design for higher output cells then?
I suspect I will get to hear that cells with a slightly low air mV, say 7-8 mV are out of specs and not safe. But my _very limited_ experience from testing something like 8-9 cells does not support that.
(Teledyne-R22D, Siemens-R22style and psr-11-39md)
None of them dropped out of linearity up to pO2 1.8 (max 3% error at 1.8 with cal at po2 1, dry testing/cal, fixed Temp) until the air mV was under ~6.5 mV.
On the other hand I did recently experience a cell that read a high 13 mV after a few months and did not pass a linearity check at all with a displayed po2 ~0.4 in _air_ after 1 bar O2 cal.
So my personal view is that a mV-test and a single point cal is not something to base a fail/pass test on, and that actually verifying the linearity (2-point testing) is more important (If possible at a pO2 >1.4).