Author Topic: EEVblog #603 - Gas Sensor Teardown - Drager Multiwarn II  (Read 12403 times)

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Offline electronics man

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Re: EEVblog #603 - Gas Sensor Teardown - Drager Multiwarn II
« Reply #25 on: April 19, 2014, 03:15:38 AM »
edit: these molecules are just chains, whith no branches, that would complicate the name a bit. im not so sure why you would have a gas sensore for that, its a liquid at room temp, it has a boiling point much high than that of water (it boils at about 150c) so its no very volatile, strange :wtf:( however it does have a flash point of 31C)

You've got to be careful with that assumption. Just because it happens to have a high boiling point, doesn't mean it's not volatile. Toluene has a higher boiling point than water, but can evaporate quite fast anyway. Similar for many of those simple hydrocarbons, they don't need all that much energy to become volatile, even if the boiling point seems a bit high.



That's why I said it has a flash point of 31c
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Offline Rudane

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Re: EEVblog #603 - Gas Sensor Teardown - Drager Multiwarn II
« Reply #26 on: April 19, 2014, 03:27:14 AM »
This was really interesting, thanks Dave  :clap:. I design these type of instruments for a living, but not for Ex certification. Our stuff, as far as I know, doesn't usually go down into mines. I design hand-held particle counters and gas meters  :-DMM. I found it interesting they used that DB25 connector to the battery compartment. They must be doing some form of parallel communication with that compartment to use that type of connector  :-//? I've also never ripped open one of those sensors, well, because the ones I use are typically over $200 US. Some of them use a UV lamp and photo-ionization to detect gases (like volatile organics), but that doesn't seem to be the case for any of those sensors ... electrochemical maybe? And as for that gunk in the sensor, I had the same reaction as you ...  :wtf:
Voltage appears across and current flows through.
 

Online mikeselectricstuff

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Re: EEVblog #603 - Gas Sensor Teardown - Drager Multiwarn II
« Reply #27 on: April 19, 2014, 04:21:48 AM »
. I found it interesting they used that DB25 connector to the battery compartment.
One reason will be for intrinsic safety - multiple, seperately resistor-protected supplies from the battery, each supplying segregated sections of the circuitry
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Offline Rudane

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Re: EEVblog #603 - Gas Sensor Teardown - Drager Multiwarn II
« Reply #28 on: April 19, 2014, 04:30:40 AM »
mikeselectricstuff: that makes perfect sense.
Voltage appears across and current flows through.
 

Offline the_bread_maker

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Re: EEVblog #603 - Gas Sensor Teardown - Drager Multiwarn II
« Reply #29 on: April 19, 2014, 08:22:33 AM »
Im interested in tearing down other broken intrinsically safe products where do you get them from?
 

Offline jancumps

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Re: EEVblog #603 - Gas Sensor Teardown - Drager Multiwarn II
« Reply #30 on: April 19, 2014, 08:46:22 AM »
. I found it interesting they used that DB25 connector to the battery compartment.
One reason will be for intrinsic safety - multiple, seperately resistor-protected supplies from the battery, each supplying segregated sections of the circuitry
If the unit has logging capabilities (as indicated in the video) this may also be the connector to tap into that data?
 

Offline hikariuk

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Re: EEVblog #603 - Gas Sensor Teardown - Drager Multiwarn II
« Reply #31 on: April 19, 2014, 06:12:28 PM »
Im interested in tearing down other broken intrinsically safe products where do you get them from?

I suspect there are loads of IS devices on eBay.
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Offline max666

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Re: EEVblog #603 - Gas Sensor Teardown - Drager Multiwarn II
« Reply #32 on: May 06, 2014, 08:50:14 AM »
Intrinsic safety does NOT cover any software aspects - the hardware must be safe regardless of what the software does. In fact it doesn't even cover anything to do with the device's actual functionality - it doesn't have to work, just not be capable of causing ignition.
I thought the part about "checking every line of code" was strange   ???
Thanks for clearing that up Mike.
 

Offline acourtois

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Re: EEVblog #603 - Gas Sensor Teardown - Drager Multiwarn II
« Reply #33 on: May 03, 2015, 11:04:51 PM »

..
The sintered disc flame arrestor - this is made of metal granules that are fused together to form a sponge type structure with a very high surface area, so any flame will be cooled to extinction before it can make it through.

Totally right Mike about this sintered material. I use to sell, among other things of course, this device, which has a sintered cap. http://hannainst.com/usa/prods2.cfm?id=012004&ProdCode=HI%208666
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Offline TechSpecB

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Re: EEVblog #603 - Gas Sensor Teardown - Drager Multiwarn II
« Reply #34 on: September 14, 2017, 09:54:08 PM »
The device marked PA 6 GF 25? PA6 pylon  6, glass filled to 25%. Heat stabilized.  The device is probably a flow meter, hot-film resistor type.
 


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