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Measuring Quadrature Signals with cFP

My application involves the monitoring of winch operations where I need to display wire rope payout values and velocity.  This is accomplished by using two proximity sensors that respond to a number of targets on the drum at it rotates.  (I would be pleased to use encoders but many of my customers refuse to use them.  I'm stuck with the proximity sensors.)  The bottom line is that I have to measure very low frequencies (i.e. typically 1 to 10 Hz).  This means that  I need to measure period instead of frequency to get a reasonable amount of velocity resolution.  I need to use a quadrature signal so the system will automatically respond to payout and in-haul operations.
 
Here are my questions:
 
1)  Is there a way to use the cFP-QUAD-510 to measure period?  I don't think there is because this product does not have any outputs or an available count source.  I have one here and it works great as a counter for quadrature signals.  However, even with the lowest time base provided in MAX, the result is inadequate for velocity measurements.
 
2)  If I cannot use the cFP-QUAD-510 to measure period, then is it possible to change the time base to something other than what MAX provides?
 
3)  I'm under the impression that I'll need to use the cFP-CTR-500 for this application.  However, this product does not have phase inputs for the quadrature signal.  Is there example programming available that will use additional counter inputs to monitor drum rotation?  In other words, is there any code available to monitor the quadrature signal?
 
Thanks,
 
Dave J.
 
 
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Dave,
 
You are correct that you'll need the CTR-500 for your application, as there is no way to change the timebase of the QUAD-510.  I did not find any examples using the CTR-500 for quadrature signal inputs.  However, you should be able to use 2 of the counters to do edge counting on each of the different quadrature phase inputs (one counter counts the A pulses, another counter counts the B pulses).  Because the pulses will always be +-90 degrees out of phase, you can use the counter gates to turn off one counter when rotating in one direction, and turn off the other counter when rotating in the other direction.  It's a little hard to describe, so take a look at the attached picture:
 
Hope this helps!
-Justin
 
 
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What about making a little card with a USDigital 7084 chip to decode quadrature signal.  Also Cherry makes a unified speed and direction sensor.  I've used these back in the old days when I did not have access to sophisticated data acquisition hardware.
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Please remember that this system needs more than just direction sensing.  The counter system must also automatically count in both directions (count up or count down) without missing counts.  There is also the quadrature
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Please remember that this system needs more than just direction sensing.  The counter system must also automatically count in both directions (count up or count down) without missing counts.  There is also the quadrature
 
I'm not sure what happened...
 
Anyway, there is also the "quadrature dithering" issue that occurs when the quadrature event stops somewhere in the middle.  In this case, the counter must not run away when the sensor is physically vibrated.  (The counter may run away because the next pulse is just near to being present.)
 
I have not had a chance to digest Justin's reply.  At worse case I may use both the cFP-QUAD-510 and cFP-CTR-500 simultaneously to solve the quadrature and low frequency issues.  I like to think however, that there must be a better way.
 
Thanks,
 
Dave
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Like I said, I'm brand new to Labview and Fieldpoint, but with Rabbit boards, I've taken care of dithering when using proximity sensors and sprocket teeth by using a 3rd prox sensor.  The first two are adjusted as close to 90 degrees phasing as possible while observing the signal on a scope.  The 3rd is for sanity checking (dithering).  It is placed so that it does not see a tooth when the other two would.  The gear tooth spacing, gear tooth surface area, and sensor size is such that I have less than a 50% duty cycle.

Of course you could purchase BEI anti-dithering modules or a broadcast board that has anti-dithering features, but they would need that 3rd signal as well because they use an encoder index signal as well as signal conditioning to preclude dithering.  But that would at least simplify programming.

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These systems are typically sold to oil rigs and they would make me "walk the plank" if I told them they need a third sensor.  Using a third sensor is not an option.  We've provided this quadrature programming before using PLC's.  However, similar to you, this is my first FieldPoint project and I have an unexpected learning curve with this hardware issue.  The reason I'm using FieldPoint is because I'm very familiar with LabVIEW and this a data logging project.  I usually use DAQ cards and serial data provided by PLC's.
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