NI 9265 Outputting current to VFD

[rwolfson]

We are currently having trouble outputting a current signal to a VFD. The signal must be between 4 mA and 20 mA. An external power supply is connected to NI 9265 and the VFD is connected to one of the analog outputs of NI 9265. 

We set the blower capacity at a certain percentage using a sliding scale. That capacity is then divided by 100 to convert it into decimal form. Next, the decimal form is multiplied by 0.016. Finally, to convert this to the 4 mA to 20 mA form, we add 0.004. This number is then fed to the express VI. An on/off switch is used to control the while loop.

We believe wiring of the hardware is all correct. Could anyone help with troubleshooting the code? The VI is attached.

Thank you in advance!

[TimothyDug]

Hey rwolfson,

I think the problem is that the DAQ Assistant task is configured for "Continuous Samples". Double click the DAQ Assistant express VI, and at the bottom of the window, for "Generation Mode", pick "1 Sample (On Demand)".

This means that each iteration of the while loop is only responsible for 1 sample, not that the whole signal will only be one sample. Does that make sense? You can read more about different Generation modes here:
http://zone.ni.com/reference/en-XX/help/371268J-01/expresswb/generating_data/

Thanks for posting!