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Gas Analyser U/S

O2 analyser with problem

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Martin King 210/08/2020 16:53:40
712 forum posts
277 photos

Hi All,

Bought a bunch of instruments at auction last week and have started going through the items.

One is this O2 analyser for welding use.

mpurge 3.jpg

It is supposed to have a 4 digit readout between 0 and about 25% (O2)

so should read approx 20.84 when fired up. With a new battery it shows this readout;

mpurge 4.jpg

and nothing happens when the pump is used.

The main agent wants a whopping £150 for a new sensor which sound like a lot.

Would anyone know if these parts are available for other uses etc?

oxy 1.jpg

oxy 2.jpg

oxy 3.jpg

Any thought swould be much appeciated.

Regards, Martin

Ian Johnson 110/08/2020 17:03:25
281 forum posts
82 photos

It looks very similar to the sensors fitted in confined space entry multi gas detectors.

Try contacting hire shops who sell or hire Crowcon gas detectors or similar devices. I recommend you speak to the service dept guys not the sales office.

Edit: similar to those fitted to the Crowcon Triple plus+


Edited By Ian Johnson 1 on 10/08/2020 17:11:26

David Jupp10/08/2020 17:08:26
738 forum posts
17 photos

Almost certainly the cell is exhausted. Typically an electrochemical cell, that is used up in presence of oxygen regardless of whether the device is turned on.

To extend life - some users cap the cell to keep air out, others nitrogen purge it after use.

Hardly mass market stuff, so won't be cheap. Is it an 'Analox' brand?

Ian Johnson 110/08/2020 17:19:32
281 forum posts
82 photos
Posted by David Jupp on 10/08/2020 17:08:26:

To extend life - some users cap the cell to keep air out

These are the same sort of people who put the detectors in plastic bags to keep them dry, and these are the same sort of people who die in confined spaces!

Martin King 210/08/2020 18:24:49
712 forum posts
277 photos

Brand is MasterPurge 100

not done it yet10/08/2020 18:55:36
4877 forum posts
18 photos

Back a long time ago, we used an Orsat gas analysers. Electronic gas analysers were available (1970s), but the sensor cells were short-lived and very expensive. Electronics have got cheaper but the cells, while cheaper in real terms, still seem to be an expensive service item.🙂

Question might be: Will it work, even if you buy a new cell?🙂

David Jupp10/08/2020 18:59:25
738 forum posts
17 photos

Ian, capping or purging the cell not only extends life, it gives much faster response time if measuring low oxygen levels (for example ppm of oxygen in hydrocarbon gases).

These sensors are used for a very wide rage of analysis - there's nothing wrong with capping or purging the sensor when it isn't being used. Obviously NOT if it is being used to continuously monitor breathing air.

Ian Johnson 110/08/2020 20:34:41
281 forum posts
82 photos

That makes sense If it's not being used in confined spaces


Martin King 210/08/2020 21:18:50
712 forum posts
277 photos

MMmmmmmm! Going in the bin I think! Thanks for the info.


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