We have two SBE19plisV2 CTD we use on a weekly basis, both in small eutrophic estuaries where DO saturation range from 0 to 250%, and the costal hyper oligotrophic East Mediterranean sea, where DO fluctuations are miniscule.
We are using the SBE 43 for many years now and until recently, these instruments were extremely reliable. We are not sure what exactly was changed, but in the last two years, the reliability of the instruments dropped dramatically, to a degree that we are now considering to switch to a different manufacture or keep a backup instrument.
1. Did anyone else find out that the reliability of SBE43 sensors dropped recently?
2. Can anyone suggest alternative sonsors that are (as always):
a. Reliable
b. Accurate
c. Cheap
d. Can be mounted on a seabird CTD
Thanks for your help
Hi, Dr. Yair!
One of the problems of membrane oxygen sensors (as well as any sensor) is limited time of correct work(possibly few years for oxygen sensors). Now most advanced technology (of course used for seabird also) is optodes. Optical sensor have many advantages in comparison with membrane sensors: fast response time, high sensitivity. independence from moving (strongly needed for membranes), more stable calibration settings, etc. Optode doesn't require changing of membrane or any other parts.
Using of membrane sensors in eutrophic waters and in highly suspended waters lead to blocking pores in membrane. This is the reason for change membrane.
Using of optodes requires just one important preconditions - this is absence of air bubbles. But in highly eutrophicated waters with oversaturation by oxygen this factor can be really critical.
I think, you can send request to manufacturer for clarification the possibility of changing the sensor.
Hi Oleksander and thank you for the respons.
I must say that by reliability problems I was not talking about accuracy, the sensors just stop working one day and if they still work they results are +-50% of the true values. This is why I asked if anyone experienced such problem.
Regarding optodes, our experience is that they suffer at least as much drift as membrane Oxygen sensors. This is also why several years ago SeaBird advised to keep using the SBE 43 (membrane) and not swich to SBE63 (optode).
Thanks again
Yair
Ok, Yair, thanks. I understand. Thank you for your experience in optodes and membrane sensors comparison.
If you checked the electrolyte and the membrane, this case may have two sources of problems: 1) sensor breakage 2) problem with the main zonde body.
We didn't face such probem.
In my humble opinnion this problem can be solved just by service specialists of seabird company.
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