why do i have noise in the Speed reading came from incremintal encoder connected to DP820
I do try to read a speed of motor from an encoder attached to its mechanical shaft,
The encoder is 1024ppr, attached to DP820
I can measured the number of pulses very well in the counter channel , but as I read the frequency/Speed value , I do suffer from a noise in the reading the value keep changing up and down even if the motor speed is steady , we do use shield cable well grounded
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Hi osama malhy,
I had the same problem with the turbine speed measurement during one of my previus commissioning. I also thought that this can be a shielding problem and lost a lot of time checking the wiring.
Please check out DP820 PRIT parameter in DTM configuration /if you are using composer tool/. What is the curent value of this PRIT /Programable Interval Time/ parameter. If it is less then 10ms try to make it a little bit bigger. You can start with 50ms.
Please, post a reply if my tips were helpful.
I can understand that value ( PIRT) could be changed/monitored if the communication protocol is Profibus the DTM then shall be active.
In my case I do use module bus, is there any access to it under the module bus??
Is there any other reason for that instability?