Measure RPM using NI USB-6008

[sombudhya]

ok...suppose if u have got no. of pulses but u dnt knw in how much time( without use of counters), is there any way 2 detect rpm of encoder or frequency of that square wave..?

[dbell0971]

Hi sombudhya,

Can you give us a better description of your application?  What are you measuring frequency or rpm's from?  Do you have any other information about the signal other than that it pulsed twice?

Thanks,

David B

[sombudhya]

my application is : "Speed control of dc servomotor". and now, as i dont have counters in my lab therefore i have devised out a method to count the number of pulses using analog i/p. But i dont know how to convert that into rpm as i dont know how to measure frequency without counters. Using tone measurements in my program is giving wrong answers below 20 hz and above 150 heartz...It will be a great help from your side if you could device me some method.

thank you

[johnsold]

To measure frequency or period using an analog input you rely on knowledge of the sampling rate.  You search through the data to find where each cycle of the pulse signal begins and ends (such as two successive rising edges). Then you calculate the period as the number of samples in one cycle divided by the sampling rate.  The reciprocal of that value is the frequency.

The RPM depends on how many pulses per revolution the sensor produces.

Lynn

[sombudhya]

thank u so much...will implement that and will come back to u within two days