What brand pH Meter should I use?

[FMIEric]

Let me start out with a little background about myself and LabView. Ok its a short one, I have been "Trying" to use LabView for about 2 weeks with no prior programming knowledge. I am looking for a specific brand of pH Meter to use with LabView 8.5. One that can be remotely controlled using LV, meaning I can control it from a PC that is running Windows XP using commands. Does anyone have any experience doing this sort of thing and if so what brand and model meter are you using? Thanks in advance

Eric Spoores

[RT4CY]

Hi Eric,

If you are new to LabVIEW, I would suggest checking out this link.  This contains many resources such as developer zone articles, white papers, and a link to our LabVIEW training site. 

Most likely you will communicate with your pH meter through serial interface.  LabVIEW ships with several examples that will get you started (Help » Find Examples…).  You can either search “serial” in the Search tab, or click on the Browse tab and go to Hardware Input and Output » Serial.

Message Edited by RT4CY on 06-05-2008 02:19 PM

[ShaunDustin]

Eric,

FWIW, I have been using a bank of DP24-PH meters from Omega.  They are not the most accurate, but they only cost $250, they have 4-20mA output that can be read through a 9203 module and a 9172 chassis. I can capture 8 channels of pH that way.  For probes I am using Sensorex epoxy body probes.  I am monitoring a waste treatment process that only requires accuracy of +- 0.5 pH unit, so I can't vouch for it beyond that.

[FMIEric]

Shaun,

Thanks for the reply, that is exactly what I was looking for. The questions I have is, could I use the Daq Assistant to set the readings up with this setup? Or is there more programming than that to be able to read it? Thanks for all your help everyone.

[RT4CY]

Hey Eric,

You can use the DAQ Assistant if all you want to do is to read from it.  Once you put the DAQ Assistant down on the block diagram, it will prompt you to choose what device and channel you want to acquire from.  You can also acquire from multiple channels on the same device, and set up some simple triggering and timing parameters in the DAQ Assistant.  To read the data, you would simply create a graph indicator and wire the Data output to it.  Let me know if you need clarification on this. 

[ShaunDustin]

Eric,

An update--I am having some trouble with using multiple meters on the same 9203 module.  The fault right now seems to be with the 9203 module, however, not the meters.  I am working with NI to get this resolved, but at this point I would not count on running multiple meters through a 9203 module.  I think it's because the 9203 requires that all the - currnet wires be bundled and run to a common ground.  The current from each meter is then no longer isolated and this results in unstable readings on the pH meters.  I'm just guessing at all this at this point, but I think that's what is going on.  If you are only lookingat  a single channel, this is probably a non-issue.

Shaun

[brutus]

Channel to earth isolation should be fine if you're just acquiring from ph meters.  Channel to channel isolation is great if you're connecting multiple high voltage devices at different ground potential.

Message Edited by brutus on 07-07-2008 08:09 PM

[ShaunDustin]

Based on my recent experience with this, I would not recommend the Omega meters.  Go for a pH meter with isolated output.  The Omega doesn't have it, and I had to buy a bunch of isolaters then use stats to clean up the noise produced by the external isolators.  Somthing like this: http://www.servonics.com/Jenco691N.PDF

[AnalogKid2DigitalMan]

I also have used Omega products unknowingly without isolated 4-20mA outputs and had to purchase isolators (from Dataforth, they have a wide range of products) all went well after they were installed.