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Mine Exploration Forum

Author Oxygen meter contamination
gNick

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Joined: 19/03/2012
Location: Pity Me, Durham

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Oxygen meter contamination
Posted: 03/12/2018 15:18:45
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I had an odd reading from my oxygen meter yesterday, when I got back to the Assay House, I was getting a reading of 19.5%
Given the unsealed nature of the building, especially with the door open, this seemed a bit unlikely and the reading was the same outside.
The meter had got a bit spludged with some ochre clay so I wonder whether this was clearing some of the oxygen out of the air and skewing the reading?

I've given the meter a clean and it is reading fine now, albeit giving the slightly unnerving reading of 20.4 in the office, outside is reading 20.9 so I'm fairly sure that the meter isn't at fault.

Has anyone else had this sort of behaviour?

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The Fresh Prince of Portreath

Joined: 05/08/2015

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Oxygen meter contamination
Posted: 03/12/2018 16:32:27
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Bearing in mind the oxygen sensor uses some chemical magic to produce a potential and that is amplified and converted into a reading, there are a number of possibilities.

1. The sensor is on it's way out.
2. The circuit is on it's way out.
3. The sensor got mostly obscured (the reactive surface) and as a result, enough oxygen was held near the sensor to result in a low reading.
4. There was another trace in the air, which was also reacting with the sensor causing a high/low voltage resulting in an erroneous reading.
5. Someone had farted.
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gNick

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Oxygen meter contamination
Posted: 03/12/2018 16:36:39
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The Fresh Prince of Portreath wrote:

Bearing in mind the oxygen sensor uses some chemical magic to produce a potential and that is amplified and converted into a reading, there are a number of possibilities.

1. The sensor is on it's way out.
2. The circuit is on it's way out.
3. The sensor got mostly obscured (the reactive surface) and as a result, enough oxygen was held near the sensor to result in a low reading.
4. There was another trace in the air, which was also reacting with the sensor causing a high/low voltage resulting in an erroneous reading.
5. Someone had farted.


1. Replaced a few months ago
2. Working now
3. Possibly
4. Meter was misreading in several places so unlikely unless being generated locally
5. It's an oxygen meter not a flammable gas meter Big Grin

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SarahBe

Joined: 24/03/2017

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Oxygen meter contamination
Posted: 11/12/2018 21:27:38
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As the fresh prince says these sensors are chemical membrane so in general have a fairly short lifetime and can get poisoned by high concentrations of chemicals etc. so even if they have been replaced fairly recently they can become poisoned in even one event.

We have had readings like that on our O2 sensors, generally due to the atmosphere or crud it's been dunked into.

Could possibly look to blow some air across the sensor to try clean it...though it sounds like the clay removal has worked. Could also look to get a calibration gas cylinder to convince yourself it's working.
What gas meter do you have? Happy to take a look and run some calibrated span gas over it if you are anywhere near Manchester Roll Eyes

Toodles
Sarah
IP: 86.147.212.169 Edited: 11/12/2018 21:31:26 by SarahBe
Cat_Bones

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Joined: 07/06/2007
Location: Shropshire

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Oxygen meter contamination
Posted: 12/12/2018 12:40:33
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Mine got set off by bad air venting from a small working in coal measures (didn't know it could happen but should have been alerted by the dead bird lying by the entrance!) and never worked after that... whenever it was switched on, it gave a low O2 alarm. I know it was bad air because I failed to put two and two together and went in anyway and almost choked to death. Lesson learned... no point having a meter if you're going to second-guess it. IP: 188.70.36.8
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