I want to acquire the radial run-out (radial small displacement) of a rotating spindle using a capacitive sensor. To do so I will use the LabView v. 7.1. The PCI-6036E card from National Instruments (NI) will be utilized for data acquisition. The spindle turns at 100 rpm and a rotational incremental encoder is fixed at rear of spindle. This encoder provides an index digital pulse per revolution. This pulse should be used to start and finish the sampling process. I want to sample on the basis of time, by means of sampling rate of the card (Ksamples/s). So, let us suppose that I want to acquire 500 data/rev. The spindle takes 0.6 sec to complete one revolution. Thus, the required sampling rate is Fs = 500 samples/0.6 s = 833 samples/s. So, I should set the VI in LabView so that it samples only 833 data/s. Therefore, I will have to reduce the sampling rate of the analog-input channels in use. For example, let us suppose that the card provides 100 Ks/s when operating in multiple channels. Let us admit that there are 4 analog-input channels in use. So, the scan rate per channel is 25 Ks/s. This is too much for this application. I only need 833 samples/s. So, I should program the VI so that the card provides that required sample rate. As said earlier, I need to start and end the sampling process at the same point. Thus, to do that the index pulse of the encoder will be used. Also, I want to sample during 5 consecutive revolutions of the spindle. So, by means of a loop in VI, I should count the index pulse of encoder until the number of pulses be equal to 5 (= number of revolutions). At this instant, the sampling process should be stopped. Note: 1) the sampled data should be put in a buffer. After the sampling process is finished, this data should be saved in a file of LabView; 2) In fact, the data acquired by the sensor are voltage analog input. Questions:1) Could you make a VI for this problem, please? Note: you can use the DAQ ASSISTANT EXPRESS VI or DAQmx TASK NAME CONTROL method2) What should I do to stop the data acquisition at the end of 5 revolutions using the index pulse of encoder?3) Could you send examples (VIs) similar to my problem above?In anticipation, thank you very much for any help. My e-mail: bruceam801@hotmail.com
