FP-AI-110 & FP-TC-120 Speed w/ LV

[wa5ycg]

Boys & Girls:

I have a FP system with an AI-110 & TC-120.  I am using the standard LabVIEW FP Read (Polymorphic).vi to read all channels at once as fast as it can.  To my amazement, each channel only updates about once a second.  I see the same responce running the test in MAX.  What am I doing wrong.  I thought that this would be hundreds of times faster.

Steve

on assignment in Germany

[Wayne.C]

Steve,

I agree it should be faster.  There are at least 3 things I can think of that will affect speed.

1 - Your vi has something in it that is slowing you down.  Suggest you post your vi.  8.2 seems to be a version that most forum users can open.

2 - How is your FP connected to PC?  Serial port, ethernet?

3 - What filtering options did you select in MAX for your FP I/O channels?

[wa5ycg]

The VI is the standard FP function from the functions palette, requesting a read of all channels as a array of doubles.

The filtering is set to 50Hz (I am in Europe).  I changed it to none, but did not seem to have any affect.

I am communicating over RS-232.

S

[Wayne.C]

What BAUD rate for RS232?

[wa5ycg]

the max, 115200 baud

[Wayne.C]

If you have it, I suggest you use the Profile>Peformance and memory tool in LV to analyze your vi and figure out exactly why this vi is so slow.

[JeffOverton]

I've noticed this also, and I have verified that my subvis are executing in single digit milliseconds.  I think the fieldpoint hardware does not update more than once every 600 or 700 milliseconds (as in, it will quickly return the same value many times for 600 ms before updating from the sensor).

[Wayne.C]

wa5cg,

I misinterpreted your initial post as possibly some sort of problem communicating with the FP.  I expect a FP Read to take a couple of mS max. 

After reading Jeff's post and rereading your intial post I don't think the delays you mentioned are slow execution of the FP Read.  Based on the fact that you mentioned MAX, I'm pretty sure that your problem is the update rate of the actual modules.  As Jeff has pointed out, multiple FP Reads will return the same value if you are trying to read the I/O faster than the update rate.

Published 'All Channel Update Rate' for the AI-110 is 5Hz to 0.66Hz depending on filter settings.  With filters off, it will take 200mS minimum before multiple FP Reads will return the new value.  In comparison an AI-118 has a published all channel rate of 10.42kHz with filtering turned off.

Published 'All Channel Update Rate' for the TC-120 is 0.88 Hz.  No option to turn filtering off on the TC-120.  TC-125 does have the option to turn the filtering off and has an update rate of 4.5Hz.

This all goes back to the fact that most of the FP modules have been optimized for industrial control and monitoring.  Very rugged with isolation and filtering, not very fast when compared to something like a DAQmx device.