Denver Instrument Model 250 pH meter won't take commands from Advanced Serial Write and Read.

[ericrlich]

Hello,

I am trying to use LabView to log values from a Denver Instrument Model 250 pH meter (manual: http://www.denverinstrument.com/denverusa/media/pdf/op-man-200-series-rev-d.pdf). It is connected through an RS232 NULL  cable to the COM1 port of my windows XP machine. To get started, I downloaded Advanced Serial Write and Read.vi. When I prompt the pH meter to print it's datalog, I receive the read string just fine, however, I have been unsuccessful at sending it string commands through the "string to write" window. The program times out and throws the following error: VISA:  "(Hex 0xBFFF0015) Timeout expired before operation completed." I am not sure what is going on, since I tried communicating through Hyperterminal and it worked. The string I tried is SET CHANNEL A PH and GET CHANNEL A.

Thanks a lot.

[johnsold]

That is a pretty poor manual as far as the communications is concerned.  It maks no mention of the port parameters such as baud, stop bits, ...

Often when Hyperterminal works and communicating with LV does not, it is because you have failed to include the termination characters.  The manual makes no mention of termination characters, but the nature of the commands (variable lengths and formats) makes it more likely that they use a termination character.  Try appending carriage return, line feed, or both to see if that gets your communication working.

Lynn

[ericrlich]

Thanks for your reply, Lynn. The serial port parameters are set up correctly, since I can change them through the meter's interface. They are set at baud = 9600, 8 bits, even parity and 1 stop. I have tried, as you said, appending \r\n at the end of my strings and it still didn't work. Any other ideas would be greatly appreciated.

Thanks again.

[Dennis_Knutson]

Try adding a delay between each character. If I remember, Hyperterminal does this automatically. Some instruments are slow in processing incoming data and need a millisecond or two between characters.

[Esteban.R]

Hi

Have you try communicating with the device using a HyperTerminal or a console like PuTTY or Portmon.

Also in the web page ni.com/drivers in the section “Go to Third Party Instrument Drivers” if you look for drivers of Denver Instruments and you could find this one “Denver Instruments Accumet” for a ph/ion meter device.

http://sine.ni.com/apps/utf8/niid_web_display.model_page?p_model_id=2374

Regards

Esteban R.