How Fast Can I Read an Analog Input from my National Instruments 733x, 734x or 735x Motion Board? Hardware: Motion Control>>Controllers>>PCI-7350, Motion Control>>Controllers>>PXI-7330, Motion Control>>Controllers>>PXI-7340, Motion Control>>Controllers>>PCI-7330, Motion Control>>Controllers>>PCI-7340
Problem: The analog inputs on the 733x, 734x, or 735x series motion boards can not be set up as hardware timed inputs when acquiring values into LabVIEW. Only through polling, or continually reading an input with a software timed loop, can motion board analog input values be quickly obtained. Solution: Using a 3.2 GHz P4 computer with Windows XP running a loop with only a Read ADC vi, loop rates of ~500 Hz were obtained (see attached LabVIEW 7.1 vi - Test_Motion_AI_Rate_LV). This rate will vary with the complexity of the vi loop and system configuration. Another way to read in analog inputs is through an onboard program (only available on 734x and 735x motion boards). A simple example was written and tested on a 7342 motion board (see attached LabVIEW 7.1 vi's: Test_Motion_AI_Rate_Onboard and Test_Motion_AI_Rate_Onboard_Host). Loop rates of ~200 Hz were obtained with this method when only the onboard program was running and no additional calls were made to the motion board from the host. Loop rates of ~120 Hz were obtained when a host program was polling the onboard program for the latest value of the constant that the analog input value was saved in. Note: These rates were averages taken over 5 to 15 seconds and will not be consistent in non-Real Time operating systems due to the nature of the execution of software loops. Related Links: Motion Control Products Attachments:
Report Date: 04/13/2005 Last Updated: 05/06/2005 Document ID: 3KCGD4MQ |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
