tachometer:: speed become zero during work

[mangood]

HI 

i have a a tachometer that conenected to motor shaft  

the output of this tachometer is pulses and each 24 pulse give a 1 revoluation

i use labview FPGA to estimate the pulse frequency  with LV VI that already provided by NI as shown in figure (1) the loop tested under 5MHZ

the problem is shown in figure (2)  where during DC rotating the pulse frequency go to zero for then back again to normal.

this cause a problem in my speed control system.

best regards

[srm@viewpointusa.com]

debounce your input.

[mangood]

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srm@viewpointusa.com wrote:

debounce your input.

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Really !!! As I read before the bounces happened in switch ?? 

[FmTesla]

Hi mangood.

Probably, Stu is right. Here is a little document that might come in handy. 

Rudimentary Circuit to Eliminate Glitches/Bounces on a Signal
http://digital.ni.com/public.nsf/allkb/93FA5F2325B220108625724500740A1D?OpenDocument

[mangood]

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@FmTesla wrote:

Hi mangood.

Probably, Stu is right. Here is a little document that might come in handy. 

Rudimentary Circuit to Eliminate Glitches/Bounces on a Signal
http://digital.ni.com/public.nsf/allkb/93FA5F2325B220108625724500740A1D?OpenDocument

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i will try 

[srm@viewpointusa.com]

I recommend a simple software debounce.  it has been very effective in the past.

any equipment that vibrates and product spurious edges on a tach or encoder.

see attached.  it is a modified version of one from NI  set n= 5 0r 10 for your case and see how it works