Reading simulated encoder with 6602

Question

Hello!
I'm trying to read quadrature encoder (to be more specific this is an output of the pulse train generator that simulates the encoder).
In the attached picture you can see how the signal that i'm trying to read.
I need an advise about the correct filter settings.
Please also see the attached vi.
Usefull data:
Labview 8.2.1
Capturing device PXI-6602.
The Encoder is 16384 pulses. (If the reading is x4, i should get 2^16 - 65536 ticks).
The Encoder has differential outputs, but i've connected only A,B and Z.
The rotating speed is up to 5000 rpm. You can see in on the picture. (16384*(5000/60)=1,365,333MHz).
There is no problem to read the encoder with another devices, i have a motion analyzer from Control&Robotics solution and it works great.
Thank you.
Elman Izia.
001.jpg (78 kb)
Position capture.vi (171 kb)

Answer 1

Hi Elman,
The filter clock is used to make sure that your signal has
integrity and eliminates glitches.  In
order for signal to be counted, it must remain high for two consecutive periods
of your filter clock.  There are five
time bases (5us, 1us, 500ns, 100ns and programmed) that can be used as your
filter clock.  The programmed clock can
be created by another counter and this setting will let a signal be counted if
it is at least twice times the filter period.
This is a great method to help eliminate errors that can be
introduced by noise, crosstalk or transmission line effects.
The TimebaseSrc property is going to select a clock to be
used as the source.  In your example that
property is correct, you would want to use the 80MHz clock.  The TimebaseRate property is going to be used
to divide the clock down to specific frequency. 
It will divide the master clock down by an integer value and round it to
get a rate that is as close to the value entered.  I would recommend leaving this number as
80MHz. 
The MinPulseWidth property is going to determine the clock
of the filter clock.  This property is
going to use the TimebaseRate property to create the predefined filter clock
settings.  If your signal stays high for
two consecutive periods of the minimum pulse width, then it will be counted. 
You need to determine the minimum pulse width that is
acceptable for your application.  Since
your signal has a pulse width of about 360ns, you might want to use the
predefined filter clock of 100ns.
In short, you are creating a digital filter that will only allow
a signal to be recognized if it remains high for two consecutive pulses.
For further explanation, refer to the PCI/PXI–6602 User
Manual page 3-20.
http://www.ni.com/pdf/manuals/322137a.pdf
Respectfully,
Rob F
Test Engineer
Condition Measurements
National Instruments