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From: UMN CEMS on 5 May 2008 18:10
Rasheel,
 
I put the VISA Configure Serial Port VI, as well as the VISA Close VI outside of the loop (I kept the VISA CLR VI inside the loop), but I still continue to get variations in temperature and mA readings.  However, there is never any "disturbances" in the voltage reading.  Any other ideas?
 
Thanks for your help!
From: UMN CEMS on 6 May 2008 17:10
MXI,






MXI Master wrote:
Are you expecting outputs that are pretty much constant or do you expect them to change often?




The temperature outputs are from a distillation column which will eventually reach a steady state over time.  Therefore, there won't be any frequent changes in these values, but a semi-accurate plot is needed (and the temps should never display a reading below zero- which is what I get during "disturbances").
 
The voltage output, which is a measure of pressure, should not change much at all and the mA output, which is a measure of a feed flow rate, will be at constant values most of the time.






MXI Master wrote:
Does it always spike up of 20.00 or is that just an example of behavior? Is 20.00 in your expected range, maybe the device is sending us a error code.



It is the mA output ("flow rate") that spikes up to ~20.00, which is the maximum output by the flow meter (4-20mA).  I do not believe that 20 should ever be in the range that corresponds with appropriate flow rates.
 
Also, when I lengthened the delays in the program, I continued to get the same behavior.
 
Thanks for your help and suggestions!

 
From: MXI Master on 6 May 2008 12:40
UMN, I have a couple ideas we could try:Are you expecting outputs that are pretty much constant or do you expect them to change often? We could treat spikes as bad data and filter them out if every point is not crucial.Does it always spike up of 20.00 or is that just an example of behavior? Is 20.00 in your expected range, maybe the device is sending us a error code.As you mentioned it is possible the delays are not proper lengths for your device, you can try lengthening them and then and see if we get the same behavior. If not we can start shortening from there.Good luck!
From: Sputnikrent on 7 May 2008 14:40
Hi UMN, Is there a reason why you have the VISA CLR VIs in between writes? Try removing that VI and see if that makes a difference. Other than that it looks like you are doing everything right, i can't really think of anything else you could to do change things to make it work. I imagine that the only difference between reading just one measurement and reading multiple measurements, is that instead of sending the same VISA Write command all the time, you are writing three different commands to the instrument turn by turn. Is this correct? Or are you handling reading a single type of measurement differently?
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