EBME Forums Forums Maintenance Technical Assistance Aftermarket O2 cells for Cosmed K4b2

We've been informed by Cosmed that they no longer supply replacement cell kits for the K4b2.

Unfortunately, we can't justify spend on the K5 as the K4 is only used occasionally for teaching and student projects.

Looking at the O2 cell, it's looks like an off-the-shelf cell that's been slightly modified to have right angled ports instead of the threaded connector. Unsure of what cell it could be however.

If you can measure the mv voltage curve corresponding to different oxygen concentrations?
You can use compatible oxygen sensors or modify the proportional resistance value inside the oxygen cell to meet your requirements.

Try Steve (Technical Support Manager) at Viamed - he was really helpful when I was looking for an oddball fuel cell.

I don't think that would be reliable, as far as I'm aware these cells begin to degrade once breaking the seal. They are marked with an expiry date. We don't have a new one to gather reliable values from, unfortunately.

Is there a direct address to get him on? Or should I just contact their technical address?

DM sent

You need a millivolt generator,Connect the millivolt voltage generator to the original oxygen battery connection port.Observe the oxygen concentration displayed by the host and record the corresponding millivolt voltage value at this time.

Complete the curve from 0%-21% oxygen concentration to 100% oxygen concentration.

Then buy other types of oxygen cells to match the curve you measured and you are done.

Sadly, Steve left just last week according to Viamed. No one else would help because it's a "modified special". I suggested I could try to give them information to inform on a replacement (that we could modify in house) but no such luck.