measure rpm and PWM signals using digital input of NI9401 module

[CUA]

Hi, is there a simple way how measure rpm (to 5000 rpm) and PWM (about f=3kHz) signals using digital input of NI9401 (ultrahigh-speed digital I/O)  module plugged in NI 9172 ?  I will wellcome any suggestions and VI examples (bether still). I'm begginer using LView 8.2. I apologize for my poor English. Many thanks.

[CUA]

Can anybody help me or it is imposible measure Frequency and PWM with this equipment ?

[Yardov]

Hi CUA,

Since you have already the right tools, you just need to get started with the software. The NI-9401 will give you access to the counters that are inside the cDAQ chassis 9172.

You need to place the module in slots 5 or 6. You can read in how they work and how to configure them in the counters section of the user guide found here.

Now to measure rpm, you can either measure the period of the signal (seconds) and multiply by 60 to have minutes and the number of ticks per revolution. You can find a shipped example to read period called “Meas Dig Freq-Buffered-Cont-Large Range 2 Ctr.vi” found under Hardware Input and Output » DAQmx » Counter Mesurements

To measure PWM, it is similar procedure and you can read the semiperiod (high time or low time). There is also a shipped example called “Meas Semi-Period.vi” found under the same location.

There is great information for these kind of task at this page or just post back if you need to.
Hope this helps.

[CUA]

Hi, I tried both examples Meas Dig Freq-Buffered-Cont-Large Range 2 Ctr.vi and Meas Semi-Period.vi. I obtained erros  both cases ( 200284 for  first exmple and 200474 for the second). When i run Count Digital Events.vi on the same channel (cDAQ1Mod5/ctr0) everything is in order and counter normaly cound down or up. Where is my problem ?

Many thanks for you reply.