Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: codiak on September 27, 2010, 10:33:18 AM
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I'm looking for the best way to connect a Teledyne R22D Oxy Sensor to the Axon II.
The sensor datasheet can be found http://www.globalspec.com/datasheets/15/TeledyneInstruments/F989C301-0E35-4889-8E7F-EE4C2A94C761 (http://www.globalspec.com/datasheets/15/TeledyneInstruments/F989C301-0E35-4889-8E7F-EE4C2A94C761)
Short version:
In the presence of Oxygen the sensor generates a current between 0-100 millivolts based on pressure and percent of O2 present.
Is leaving the reference voltage at 5v and using op amp with a gain of 50x the right way to approach this?
If so: any recommendations of op-amp vendor?
Is there a better way to go about this?
Thanks!
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Hmmmmm thats not a link to a datasheet, and I'm not signing up for an account with them :P
generates a current between 0-100 millivolts
A voltage or a current? :P
If voltage, then yes, you should use an op-amp. Op-amps tend to not be so accurate after around 20x amplification, so check the datasheets. You can always use more than one op-amp in series.
I recommend just powering up the sensor and using a voltage meter first to see what voltages you get, that way you'll know better of what kind of amplification you'd need.
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Hmmmmm thats not a link to a datasheet, and I'm not signing up for an account with them :P
Same here....
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Hmmmmm thats not a link to a datasheet, and I'm not signing up for an account with them :P
generates a current between 0-100 millivolts
A voltage or a current? :P
If voltage, then yes, you should use an op-amp. Op-amps tend to not be so accurate after around 20x amplification, so check the datasheets. You can always use more than one op-amp in series.
I recommend just powering up the sensor and using a voltage meter first to see what voltages you get, that way you'll know better of what kind of amplification you'd need.
Don't blame you... though I didn't find an alternate...
regardless, it is in millivolts and is voltage... so Op-amp it is.
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Hi,
[...] Op-amps tend to not be so accurate after around 20x amplification, so check the datasheets.
That statement is valid when you are scraping upon either the gain-bandwidth product or the slew rate. At near DC, as an oxygen sensor output is, there shouldn't be any problem with a current rail-rail amplifier.
codiak <- According to several divers sites, this particular sensor has an output stated as +/-10mV, not the 0..100mV stated by you.
Not sure of the +/-part though, but perhaps it can detect antimatter, or at least anti-oxygen :P
If it is for anything health-critical, I'd advice against homemade gizmos lacking Quality Assurance!
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codiak <- According to several divers sites, this particular sensor has an output stated as +/-10mV, not the 0..100mV stated by you.
Not sure of the +/-part though, but perhaps it can detect antimatter, or at least anti-oxygen :P
+- is the warning that results will vary... the device will decay over time
+/-10mV is what a fresh sensor will read 20.9% O2 (IE Air) at Sea-Level....
mV will increase as percent of 02 or ATM pressure increases and is linear in nature.
100% 02 =~ 55mV
100% 02 at 2 Bar =~ 95mV
Meters using these sensors need to be recalibrated with a known/trusted air supply prior to use.
If it is for anything health-critical, I'd advice against homemade gizmos lacking Quality Assurance!
I'll be sure the lawyers are the first users... ;-)
For my purposes it's not in the critical loop
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Hi,
Meters using these sensors need to be recalibrated with a known/trusted air supply prior to use.
Ah, then long term stability is not a priority - blasted sensors, not manufactured anymore and with a 3 year lifespan.
I seem to recall something about a guy experimenting with using zinc/air cells for oxygen sensors with pretty good results, although they needed recalibration now and then as well - but a zinc/air cell is cheap, the RD sensor is not.
Don't recall if he researched it for diving purposes though.
Maybe a quick Googling will get you there, if you are interested.
I'll be sure the lawyers are the first users... ;-)
For my purposes it's not in the critical loop
I was more concerned about the implications of you diving in with a bunch of loose wires ;D