Slow Velocity Measurement Using cFP QUAD-510

I want to use the cFP QUAD-510 Module with a 1024 Count Per Revolution Quadrature Encoder to get velocity, direction, and placement of a rotating shaft. The shaft is a VERY SLOW ROTATING SHAFT, about 1 revolution per 7 seconds, or .143 rps. The encoder frequency is 1024 X .143 which comes to 143.432 Hz. I have two questions:
1. Since the velocity counter registers in the QUAD-510 are fixed in microsecond references, will I get a meaningful resolution out of the registers with an encoder freq. of 143Hz?
2. Is 143Hz too slow for the QUAD-510 and should I just change over to an absolute encoder with a DIO Module and do my own velocity calculations with loops and longer time bases?
I know the quadrature will work for placement and direction. But I am not sure if this is the right application for velocity.
Ron Kocol

Ron-
Due to how slow your encoder is running, I can’t guaranty the accuracy of the velocity readings from the counter references. A better way to do this would be to simply take the derivative of your position (dx/dt). This way it will be as accurate as possible.
Regards,
Mike S
NI AE

Similar Messages

CFP-Quad-510 velocity configure

Is there a way to programmatically configure the timebase for the quadrature channels from within the LabVIEW environment?
Ryan Vallieu
Automation System Architect

I found the VI in the VI.lib under FieldPoint\Configuration\Configure Range.llb
It looks like it will work - for clarity here is a picture of the VI and the Input Range constant and the Channel numbers that would apparently be needed. Module address would need to be 1-to-[max module #] depending on which module in the system it is.
I don't have a module right now to test this VI with, so if someone does have one and can verify that this VI works with the cFP-QUAD-510 as well as the original intended target of the FP-QUAD-510, I would appreciate it.
I am really interested in knowing if this will work with cFP-QUAD-510 modules in a cFP-1804 chassis.
Message Edited by RVallieu on 07-02-2008 09:36 AM
Message Edited by RVallieu on 07-02-2008 09:37 AM
Ryan Vallieu
Automation System Architect

CFP-QUAD-510 won't read encoder inputs 5V

I have a cFP-1808 ethernet interface with 7 modules attached. One
is a cFP-QUAD-510. When I hook an encoder to this module and view
velocity/position measurements in MAX, I only get valid results if I
use the module's 5VDC regulator to power the encoder. The encoder
itself can take 5-24VDC, but when I try giving it 12VDC or 24VDC, I get
no new updates in MAX (i.e. the status is successful, the velocity
reads zero, and the time stamp doesn't change from when I first started
the task). While powering the encoder with these external
supplies, I put a scope on the encoder outputs and verified that they
are 90 deg offset square waves (with amplitudes at 11V and 22V
respectively) as expected.    When I use the 12VDC or 24VDC
power supply as input to the 5VDC regulator and power the encoder off
that, everything seems to work perfectly.   The only
difference between the two cases is the voltage level given to the
encoder. The manual for the cFP-QUAD-510 claims that it can
accept encoder levels as high as 30V.   I'm testing now for a
future application where I won't have the option of powering an encoder
with the 5V regulator. What could be causing this problem?
Thanks,
Jeff

Hi Jeff,
That seems peculiar that your device is not reading counts for the higher voltages.
You may want to check out the following KB first:
My FP-QUAD-510 Will Not Count
Otis
Training and Certification
Product Support Engineer
National Instruments

CFP QUAD-510 Programming in LV7.0

I am trying to measure position using a cFP-QUAD-510. One problem is that there is no way to programmatically set the counter to a position. Another is that the counter sets itself to 2^32 counts when it goes from zero toward the "negative" direction then counts down. That is a problem when doing rotational position. Does anyone have a solution to this problem? I also have a problem finding the position using the given count because resetting after one rotation in the "negative" direction puts me bak to zero and then directly to 2^32 on the next count. My counts per revolution are 516131. So as you can probably tell I cannot divide the entire count evenly into revolutions either.
Thanks for whatever help might be out there.
James

Instead of trying to set a counter to a particular value, store your value in your program and add or subtract your offset value each time you want to read the counter.
The counters are all 16 bit according to the manual and only store the counts of 0-65535, combining two registers gives a 32 bit value. Basically a U32. If you want it to have a negative sign, try reading the value as U32 and subtract 2147483648. Or try typecasting the U32 to an I32.

Velocity readings cFP-QUAD-510, explain limitations

I am trying to understand the limitations of the Velocity measurements capability of the [c]FP-QUAD-510.
Looking at the operations manual I see the maximum velocities that can be measured in counts/us.
If I have a quadrature encoder tracking a shaft running at 1750 rpm, and the encoder is 60 PPR - this yields 1750 counts/second or 0.00175 counts/us.
Would I thus have to use the longest timebase to obtain RPM +/- 38 counts/sec which with the 60 PPR yeilds +/- 38 rpm ?
Thus I would need to increase my PPR to get me a better Velocity Resolution.**
**Is my understanding of the velocity Ranges correct?
Message Edited by RVallieu on 07-01-2008 04:30 PM
Ryan Vallieu
Automation System Architect

Hi Ryan,
This is what I have:
60 Pulses /revolution * 1750 revolutions/minute * 1minute/60 seconds = 1750 revolutions/second = 1750 counts/sec (1 revolution = 1 count)
1750 counts/sec *1sec/ 10^6 microsecs = 0.00175 counts/microsecond
Comparing this value to Page 11 of the operating instruction, the best time base for this would be 26214.14 microsecs.
Velocity range means the highest velocity value that can be measured within that rage. So for your value of 0.00175 counts/microsecong, the range of +/- 1.25 counts/microsecond would be the most appropriate since you would get the best resolution. You can, of course measure values upto +/- 1.25 counts/microsecond within the range.
I hope this helps!
Warm regards,
Karunya R
National Instruments
Applications Engineer

Low velocity measurement using 6601

I am using 6601 on measurement of position and velocity of increamental encoder. Our sevor motor rotate at very low speed. How can I measure the velocity at high accuracy at the same time of measuring the posstion of encoder.Can you provide me some tip? Thanks.

Hello;
You can use two counters to accomplish that task.
The first counter can be used and configured as position measurement. That will make the counter to give back the position of the motor.
The second counter can be used as buffered event counter. You just need to route one of the encoder channels to the counter gate, and since you know the frequency of the source, and at every event of a gate pulse, the internal value of the counter is transfered to the buffer, you can do a quick calculation with the number retrieved and the source signal frequency.
Hope this helps.
Filipe A.
Applications Engineer
National Instruments

Is there a way to preset the cFP-QUAD-510 module?

Using MAX, there is a way to reset the cFP-QUAD-510 to zero. However, is there a way to preset the counter programatically through LabVIEW to count values other than zero?

Dave,
With the 1-50 Hz range that you are trying to measure, you are correct in your assessment that the CTR-502 module would provide a more accurate reading. Just for everyone's benefit, let me give a quick explaination of why this is.
The QUAD-510 module has only eight allowable timebase settings for velocity measurements. The timebase is essentially the "window" over which your quadrature encoder signal pulses are counted, and is equivalent to the gate signal that is used when doing frequency measurements with the CTR-502. The longest window that can be applied with the QUAD-510 is 26,214.4 us, which results in a velocity resolution (accuracy) of 38.15 counts/s or 38.15 Hz. As such, when trying to measure frequencies in the range of 1-50 Hz, your accuracy will be very low.
The CTR-502, on the other hand, can get much more accurate measurements at this frequency range because you can configure a much longer window. There is a LabVIEW example that installs with the FieldPoint driver called "Frequency Measurement.vi" that shows how to do frequency measurements with the CTR-502.
Dave, if you would like to see better resolution for low frequency measurements with the QUAD-510, again, please feel free to submit a product suggestion for this functionality. For now it sounds like you have the best hardware setup for your application. I hope that the information I have provided has been helpful.
Best regards,

Cfp-quad-510 count max

I've got a loaner cFP-QUAD-510 and connected it today to see how it will work with the cFP_1804 module.
I've got external power wired to the cFP-CB-1 V and C terminals as prescribed.
The first thing I do in my simple VI is to send the Command = 1 to reset the count. This does not appear to be working.
The next read of the counts taken shows 1616969568. This does not change when I do not rotate the 60 PPR encoder.
When I rotate the encoder the counts seems to wrap to 4294967136 and then only the last 4 digits change count, but not steadily and I get 4294967136 showing up quite bit after the encoder counts down by a couple hundred.
What could be causing this? Does the cFP-QUAD-510 work with the cFP-1804 backplane?
Ryan Vallieu
Automation System Architect

Lesson: Always check the pins on the loaner equipment - found a bent one - unit works.
Ryan Vallieu
Automation System Architect

Read velocity from QUAD-510 using single phase sensor

Hello, for my application I'm using a proximity sensor to count pulses using the CTR-400. To obtain velocity, I can make some calculations based on frequency or period but I was wondering if I can delegate this annoying task to the QUAD-510 module At the moment I'm able to read velocity using an encoder, but what if I use a single phase sensor like a proximity?

Hi,
Take a look at this document that talks about measurement with single phase and QUAD-510:
http://digital.ni.com/public.nsf/allkb/5E1CBFCBF821822686256CBB005B5305?OpenDocument
Best regards
Luca Gallo
Sales Engineer
Attachments:
PID Velocity Control.vi ‏34 KB

How to use cfp ctr 502 for rpm measure+cfp configure in labview

i'm new in handling cFP's,i need to measure rpm of an engine using cFP CTR 502.Plz i need detail regarding which method either pulse counting or frequency method is required for my application,Plz also tell me is there any possibility of configuring cfp using labview

Hi,
please see the following link to NI-Discusion forum. There is simaler question.
http://forums.ni.com/ni/board/message?board.id=110&message.id=1764&requireLogin=False
I also send you tow links to LabVIEW examples. I hope it helps.
http://venus.ni.com/stage/we/niepd_web_display.DISPLAY_EPD4?p_answer=&p_guid=BCB1261CBE2635D2E034080020E74861&p_node=174404&p_rank=&p_source=Internal&p_submitted=N
http://venus.ni.com/stage/we/niepd_web_display.display_epd4?p_guid=BCB1261CBE2635D2E034080020E74861&p_node=
TN

Velocity Measurement from FPQuad-510 encoder pulse counter

Hi, I have a quad-510 quadrature encoder counter and a 1024pulse/1rotation encoder. How can I read or calculate angular velocity(accurately and without much delay) from encoder readings?
Is there a special vi or another algorithm (other than derivative.vi) that could help?
Thank you.

Caner,
What do you see listed for the status of the velocity channels in MAX?
Also check your channel configuration to make sure you have an appropriate range set.
Regards,
Simon
Message Edited by Simon H on 02-02-2007 06:50 PM
Attachments:
MAX_CTR.png ‏26 KB
MAXDataConf.png ‏11 KB

Velocity measurement from low resolution encoders

Hi, I have 1024 pulse/1rotation encoders. I want to calculate or estimate angular velocity from this low resolution encoders. When I use dx/dt(derivative.vi) there are high and low readings which obviously seem wrong to me.I want to have a more smooth and accurate reading(and without much delay). Is there an efficient and accurate way of reading velocity measurements from this low resolution encoders? FOr example does Ni/Motion help? Or is there a velocity measurement .vi ?
Thank you.

As far as I remember (*) , the FP-QUAD will measure the velocity by counts during a fixed time slot. The maximum time is (was?) 26.??ms.
Your resolver has 1024 pulses (I assume 2 pulse streams with 90° shift) , the QUAD will count pulse edges, so you get 4096 counts per revolution. Together with the integration time (26.??ms), you get a resolution of 38.15 counts/s (See manual of the FP-QUAD) or an error of +/- 0.559 RPM
Of course you can read the 32bit counter of the QUAD in a user defined time periode and calculate the velocity.
If you have real slow movements, you can measure the time between each pulse. The accuracy will depend on the quality of your resolver and the resolution of your timer, however I think this couldn't be done with the FP-QUAD.
* My last task with FP-QUAD was 4 years ago, maybe new firmware and driver give you more choices now
Greetings from Germany
Henrik
LV since v3.1
“ground” is a convenient fantasy
'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'

How reading Rpm speed from fp quad 510

I have an encoder of 2500 ppm quadrature differential signal, and i link
this with a FP_quad_510
The value reading count/microsec how is possible to transform in RPM?
Why if i use the FP configurator in the edit device/channel if i setting a
range of -1,25_1,25 coerce the value range at the default range setting?
Courtesly i would like information of field point quadrature encoder end
reading position,speed,reset on the revolution exc.
Thank for answer Nicola

Thank's for answer,
Now i have try to coerce the 1,25 range and i select customer value.This
mode bring the 1,25 range.
Nic
"Pravin B" ha scritto nel messaggio
news:[email protected]..
> Nicola,
> As for converting the count/us into a RPM reading,you will have to do
> it inside your software program. It's gonna depend on the
> counts/revolution on your quad encoder. You can then mathematically
> calculate the RPM and display that on your panel.
> Ex: 'count/us value' / (1,000,000*60) = counts/min
> > 'counts/min' / (counts/rev of your encoder) = RPM
>
> I am unable to follow the second question but if you mean that your
> count values coerce when set to +_ 1.25 velocity range setting, it
> could probably be
becuase the velocity resolution at that range is
> 38.15 counts/s and so you may not be able to see smaller counts.
>
> You can find more information about the position counters, velocity
> measurement(speed), index status etc in the FP QUAD-510 Operating
> Instructions Manual at : http://www.ni.com/pdf/manuals/322633b.pdf
>
> To program the QUAD-510 'Reset', right click on the FP-QUAD-510 @x and
> choose Edit This Device. Then click on Channel Configuration. In the
> Channel Commands box, press the button that says Create Item. This
> will create a channel named "Control @Ch0". You can then write to the
> "Control @Ch0" item as if it was a normal output. Anytime in your code
> that you write a value of 1 to the "Control @Ch0" item, it will reset
> Axis 0 (channels 0 and 4). To change which channel you are resetting,
> simply change the checkboxes before pressing the Create Item button.
>
> Hope this helps,
> Pravin

How to reset a FP-QUAD-510 with CVI ?

I use a FP-QUAD-510 with FP-1600 ethernet module.
In my CVI application, I want to programmatically reset the position counter.
Is there any sample source code to do such operation ?
Thank you in advance
Chris

Chris,
I do not have any sample code that I can send you, but I can tell you how to do it. First, in FieldPoint Explorer, right click on the FP-QUAD-510 @x and choose Edit This Device. Then click on Channel Configuration. In the Channel Commands box, press the button that says Create Item. This will create a channel named "Control @Ch0". You can then write to the "Control @Ch0" item as if it was a normal output. Anytime in your code that you write a value of 1 to the "Control @Ch0" item, it will reset Axis 0 (channels 0 and 4). To change which channel you are resetting, simply change the checkboxes before pressing the Create Item button.
Regards,
Aaron

Slow interface when using 9-slice symbols?

Hi,
Just wondering if anyone else experiences really poor performance within the Flash application when using 9-slice symbols?
I'm using a Quad Core 9300 with 4GB ram, 512mb 780GTX, Windows Vista (32bit) and CS4 with dual 24" screens. I have noticed it's slightly better in CS5 with Windows 7 but still experiences similar problems.
I am wondering if maybe it's related to the dual screen setup. I will try disabling one next.
By slow interface, I mean clicking on a symbol might take 4-5 seconds to register. Double clicking it, another 4-5 seconds, moving it a single pixel, 4-5 seconds etc. It gets worse the more symbols there are on the stage. Hide the layer with them on it and it runs fine.
I've tried using XP compatability mode, disabling windows aero all with no success.
I'd be very interested to hear if other people have this issue and if anyone has a solution!
Cheers,
Joolz

Hi,
Just wondering if anyone else experiences really poor performance within the Flash application when using 9-slice symbols?
I'm using a Quad Core 9300 with 4GB ram, 512mb 780GTX, Windows Vista (32bit) and CS4 with dual 24" screens. I have noticed it's slightly better in CS5 with Windows 7 but still experiences similar problems.
I am wondering if maybe it's related to the dual screen setup. I will try disabling one next.
By slow interface, I mean clicking on a symbol might take 4-5 seconds to register. Double clicking it, another 4-5 seconds, moving it a single pixel, 4-5 seconds etc. It gets worse the more symbols there are on the stage. Hide the layer with them on it and it runs fine.
I've tried using XP compatability mode, disabling windows aero all with no success.
I'd be very interested to hear if other people have this issue and if anyone has a solution!
Cheers,
Joolz

Slow Velocity Measurement Using cFP QUAD-510

Similar Messages

Maybe you are looking for