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General Category => Do-more CPUs and Do-more Designer Software => Topic started by: dustin.elliott on June 11, 2019, 07:03:26 PM

Title: Analog Output Counts
Post by: dustin.elliott on June 11, 2019, 07:03:26 PM

Hi,

I have a PID loop that running a +/-10 VDC analog output. The PID loop is set to scale the 0 to 100% to -32767 to 32767 (to match the range as shown on the system config page). The PID loop is working and I can see the counts change and the output change. However, the voltage on output isn't changing smoothly the way the counts are. From what I can tell during testing is the voltage output doesn't start changing until the counts are between approximately -5000 to 5000. This doesn't make sense per the info on the system config page. Am I missing something here?

Thanks,
Dustin

Title: Re: Analog Output Counts
Post by: BobO on June 11, 2019, 08:45:31 PM

No, it looks right to me.

If you disable the loop and drive WY0 directly, does the output do what you expect? What is WY0 driving? It is a high impedance voltage input, right?

Title: Re: Analog Output Counts
Post by: ADC Product Engineer on June 12, 2019, 09:59:31 AM

Quote from: BobO on June 11, 2019, 08:45:31 PM

No, it looks right to me.

If you disable the loop and drive WY0 directly, does the output do what you expect? What is WY0 driving? It is a high impedance voltage input, right?

I would agree, what is the impedance of the load?

Title: Re: Analog Output Counts
Post by: dustin.elliott on June 12, 2019, 04:36:14 PM

The impedance of the input is ~1 Mohm. It turns out the PLC is working properly and the motor drive it's connected to is the one responding oddly to the input. Thanks for the help.