Abdul Wajid

Analog Input fluctuation & Bits switching

3 posts in this topic

Dears

Need some help to sort out the issue of analog input value fluctuation up-down & output bit switching

I have CP1E- NA20 model PLC and pot (0-10V) had been connected to analog input from the same source 24V SMPS (omron brand) along with PLC which has 12 to 13 bit resolution(0 - 6300).

Actually i have to switch ON specific output at 3000 counts (approx 5V) and used both compare & equal instruction, but the count overrides and exceeds without switching particular output. I observed that the output gets switch ON only when pot rotation slows down upto the limit, else normally o/p wouldn't get switch ON. Meanwhile the PLC count keeps fluctuating 5 to 6 counts everytime. Also try to used another i/p terminal for another pot but same problem occurs. Scan time shows 1.3 to 1.4ms. Have used the general mov instruction 

Is there any solution to stop the input fluctuation and activate normal bits switching with pot ? Does scan time interferes/not enough in the high speed or immediate bits switching ?

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14 hours ago, Abdul Wajid said:

Actually i have to switch ON specific output at 3000 counts (approx 5V) and used both compare & equal instruction, but the count overrides and exceeds without switching particular output.

It sounds like you need a range to turn on your output. Example:  > 2995 AND < 3005.

14 hours ago, Abdul Wajid said:

Is there any solution to stop the input fluctuation and activate normal bits switching with pot ?

In the PLC Settings, Built-in AD/DA tab, you can click the check box for Use averaging. You can also create your own in ladder using the AVG(195) instruction.

14 hours ago, Abdul Wajid said:

Does scan time interferes/not enough in the high speed or immediate bits switching ?

This is most likely the cause. If you are only using the Equals To, then your value may only be Equal To 3000 for less than the PLC scan time, or possibly not equal at all due to the conversion time.

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@IO_Rack Thanks gentleman.... it  works better after using >2995 AND <3005 inst. but sometimes still occurs scan time issue.

Further regarding count fluctuation, by clicking check box (use averaging) in  Built-in AD/DA tab it improves & decrease the fluctuation upto 1 count and rarely 2 counts, hope it almost works for most of the applications. Also used AVG inst. mentioning max limit as 64 cycles for particular analog i/p but the result was same, but occasionally it shows the exact count. Thanks once again helping to sort out the issue.

 

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