pH recording through a computer

[jabano]

Hi, 

I'm new to LabVIEW and was wondering if there was a way I could measure pH at a constant time/interval.

I have a pH electrode and am using it through an OMEGA PHB-600R pH meter. It can record pH manually through a RS232 serial cable but is there a way the computer can automatically update every minute or so.

Thanks

[Cory_K]

If you are already reading in data using the serial port, you can just put that code in a while loop with a 1 minute delay.

Or do you mean that you have to manually press something on the instrument to send a reading?

[jabano]

Oh i meant I have to manually press the instrument I'm using. Must I need a DAQ Card? or Is there another way I can go around this. 

Thanks

[Cory_K]

By looking at the manual, it doesn't look like there are a set of commands for communicating back and forth with this instrument.

You may want to contact Omega's technical support to see if this is even possible with this model.

[jabano]

Okay, thank you!

If there isn't a way to measure pH consistently using this device is there another way I can log pH through my computer using labVIEW? Is it only possible with DAQ hardware?

[Cory_K]

LabVIEW will help you with the communication, displaying data, logging data, etc but it does not actually do any measuring, because it is just computer software.

DAQ hardware will take care of the I/O and communication, but again, it doesn't actually do the measuring.

As far as actually measuring pH, you need to look for hardware that does that.

When you are looking for a pH meter, make sure in the specifications it says something about communication without having to manually push something.

Ask Omega if this version, or any other version, have this capability.

[jabano]

Oh okay the pH meter is connected with a pH electrode so I can probably use that with DAQ? 

[johnsold]

You cannot connect the pH probe directly to an ordinary DAQ device because of severe impedance mismatch.  From looking at the Omega datasheet for your meter it appears that no analog output is available.  So, there is nothing for you to connect to your DAQ device.

As has already been mentioned it looks like you need a different pH meter.

Some years ago I designed a system to measure signals from several pH probes.  For that system we designed special preamplifiers to boost the signal from the probes to a level suitable for use with a DAQ device.  It was a complicated and messy system and we never got it all working.  If you are not an electrical engineer with experience in the design of such amplifiers, I recommend you but an appropriate meter.

Lynn

[RavensFan]

If you already have the meter and the software that communicates with the meter, you could try using a program such as portmon to snoop on the communication protocol between the meter and the software, then see if you can replicate that in LabVIEW.