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DAQmx counter rollback

Hi

We developped a VCD in order to measure the speed of a motor. To measure this speed, we use some counter.

We use the Daqmx Create Channel function (CI Position angular Encoder) , and then we read the angular position using the DAqmx Read (counter dbl 1channel 1 sample).  Then we calculate the speed with the angular position difference and the time difference between two calls.

 

All this things works, but after a while (depending on the speed of the motor) , we have a rollback of the counter and then a false speed measurement. It is normal to have a rollback, but why isn't this rollback managed by NI when we use the angular position. The driver returns me a angle position, it should return me the good position even if i have a rollback of the counter ...

 

We found a solution in order to get rid of thi sproblem : We don't read the angle position but the value of the counter, and then we manage the rollback and we calculate the angle position from the value of the counter. But as i said, for me the driver is bugged ... 

 

 

 

 

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