DAQ question

pHaestus · 04-28-2005, 02:26 PM

Ok this is actually a work-related question but here goes:

I need to measure and log different parameters (temperature, pH, Eh, {Ca2+}, etc in a bioreactor we are building. It looks to me like the easiest way to do this is to just buy a NI DAQ card and use their free software to continuously log the data. But I am not turning up much information on using DAQ cards to capture readings from electrodes. Is this going to work ok? They output a mV reading over a pretty big range (pH 4 to 10 is a 350 mV range) so I would think that this would work fine. But is there a lot of additional smoothing/conditioning circuitry on a pH meter that I don't know about? Anyone have any reasons why trying this is a bad idea? The electrodes are all BNC so I am assuming it's relatively easy to mate them to the DAQ card's analog inputs...

TerraMex · 04-29-2005, 08:33 AM

beware of noise on those low amplitudes.

Depends on the noise you get on the lines.
Depends on the scale of the DAQ -> trying to read mV on a 0 to 5V analog DAQ, no good -> instrumentation amplifiers from mV to V.

decent noise reduction, lots of products floating around (google

) ,
several IC's from Maxim , Analog.

http://www.analog.com/en/subCat/0,28...0%255F,00.html

04-28-2005, 02:26 PM	#1
pHaestus Big Player Making Big Money Join Date: Aug 2001 Location: irc.lostgeek.com #procooling.com Posts: 4,782	DAQ question Ok this is actually a work-related question but here goes: I need to measure and log different parameters (temperature, pH, Eh, {Ca2+}, etc in a bioreactor we are building. It looks to me like the easiest way to do this is to just buy a NI DAQ card and use their free software to continuously log the data. But I am not turning up much information on using DAQ cards to capture readings from electrodes. Is this going to work ok? They output a mV reading over a pretty big range (pH 4 to 10 is a 350 mV range) so I would think that this would work fine. But is there a lot of additional smoothing/conditioning circuitry on a pH meter that I don't know about? Anyone have any reasons why trying this is a bad idea? The electrodes are all BNC so I am assuming it's relatively easy to mate them to the DAQ card's analog inputs... __________________ Getting paid like a biker with the best crank... -MF DOOM

04-29-2005, 08:33 AM	#2
TerraMex Cooling Savant Join Date: Nov 2002 Location: Portugal, Europe Posts: 870	beware of noise on those low amplitudes. Depends on the noise you get on the lines. Depends on the scale of the DAQ -> trying to read mV on a 0 to 5V analog DAQ, no good -> instrumentation amplifiers from mV to V. decent noise reduction, lots of products floating around (google ) , several IC's from Maxim , Analog. http://www.analog.com/en/subCat/0,28...0%255F,00.html __________________ "we need more cowbell."

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