pci-mi0-16e to count frequency

[black_whistler]

helloo,
i need to count frequency of squarewave from eddy current sensor. from 300 to 3500 Hz. should i use "measure frequency.vi" or "measure pulse width or period.vi" ? which one better?
i use it to count the angular speed of a rotor which got 20 tooth to measure it with eddy current sensor. i need this angular speed as the feedback for PID-speed-controller for this motor

anyone can help, pleasee...

[Sean_C.]

Hello,

Thank you for contacting National Instruments. 300 - 3500 Hz is a relatively low frequency signal. The Measure Frequency.vi uses 2 counters to measure relatively high frequency signals. The Measure Pulse Width or Period.vi only uses one counter for relatively low frequency signals. I would recommend using the period measurement method then take the reciprocal to find the frequency.

I hope this helps,
Sean C.

[black_whistler]

which pin should i connect to the signal? could you help me by sending the VI too?
here is the the connector of the PCI-MIO-16E-1

thanx alot

[black_whistler]

which pin should i connect to the signal? could you help me by sending the VI too?
here is the the connector of the PCI-MIO-16E-1

thanx alot

[Sean_C.]

Hello,

The Measure Pulse Width or Period.vi can be found by right clicking on the block diagram and selecting NI Measurements >> Data Acquisition >> Counter. If you look at the context help for this VI (Ctrl+H), you will see that this VI measures the period or pulse width of the signal wired to the counter's GATE pin. Pin 3 for CTR 0 and pin 41 for CTR 1.

I hope this helps,
Sean C.

[black_whistler]

i've got the VI. i'll use counter 0. so, i sould wire it to pin 3. and where sould i wire the other wire?
i need to ask another thing too, in this DAQ-card there is 16 input channel. can i measure 2 channel (in one VI) with different sampling rate? i've tried it, and got some error, it say someting like "the device is reserved...)

thanx

[Sean_C.]

Hello,

"so, i should wire it to pin 3. And where should i wire the other wire?"
I assume the other wire you are referring to is your signal's reference line? If so, just wire this to Digital Ground (Pin 4).

Because all AI channels share the same sample clock, it is not possible to read from 2 channels simultaneously with different sample rates. It is, however, possible to only read every N points from one channel's AI buffer. This is a way to simulate AI at different sample rates. Please see the Example Program below for more details.
http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=BCB8746152612330E034080020E74861&p_node=201213&p_source=External

Let me know if you have any further questions.

Regards,
Sean C.

[black_whistler]

and, where sould i wire the pin to count the frequency? i m a new begginer, can u tell me which 2 pin to wiere the signal ?

thanx..

[Sean_C.]

Hello,

If you are using the "Measure Pulse Width or Period.vi" on counter 0, you should wire your signal to Ctr0 Gate (Pin 3), and D GND (Pin 4).

Regards,
Sean C.