Troulbe in measurement quadrature encoder with 6601

Hi,
Thanks for Ross's help.But I cannot differ 6601's x4 mode from other counter/timer counting mode. In measurement position, what difference between them. And I just want to know whether my application viable.
We are trying to measure position with 6601. The frequency of quadrature encoder is from 100Hz to 8MHz. Now, we connet the A,B and Z channel directly to counter . Using the example in CVI, we change the filter to 100ns and use x4 mode. It works perfect at low frequency.
The problem is when the frequency of encoder is higher than 2MHz, the accuracy decreases greatly. I'd like to know about following:
1.Can 6601 do the previous task enough? Or I must change to use 6602.
2.If
6601 is available, is there any way to increase measurement accuracy ?(in software or wire connection )

>jimmyjimmy2000
"Hi,
Thanks for Ross's help.But I cannot differ 6601's x4 mode from other counter/timer counting mode. In measurement position, what difference between them. And I just want to know whether my application viable.
>>mross>The application is viable. However, the use may be difficult.
>jimmyjimmy2000
We are trying to measure position with 6601. The frequency of quadrature encoder is from 100Hz to 8MHz. Now, we connet the A,B and Z channel directly to counter . Using the example in CVI, we change the filter to 100ns and use x4 mode. It works perfect at low frequency.
The problem is when the frequency of encoder is higher than 2MHz, the accuracy decreases greatly. I'd like to know about following:
1.Can 6601 do the previous task enough? Or I must change to use 6602.
>>mross>The 6601 is just as good as the 6602 at 2MHz. Therefore, a 6602 will have the same problem of inaccuracy.
>jimmyjimmy2000
2.If 6601 is available, is there any way to increase measurement accuracy ?(in software or wire connection )"
>>mross>Yes, in the wire connection you can make improvements.
6601 can count as fast as 20MHz (60MHz with prescaling). The signal is noisy (containing addtional, incorrect information).
You must use an oscillosope to look at the signal. Look at it when 6601 is counting correctly, and look at it when 6601 is "malfunctioning".
The counter will increment whenever the signal is high for more than 5 nanoseconds. The conditions for "High" and "Low" signals must be strictly met. If the signal is greater than 0.8V, the counter may increment. The signal must then drop below 2 Volts for a "Low" to be seen.
This sounds wrong, but is true. The counter is expecting TTL signal conditions (Transistor -Transistor Logic). This specification is very broad.
A "High" will absolutely be recognised if the signal is greater than 2.0V.
A "Low" will absolutely be recognised if the signal is less than 0.8 V.
However, the range from 0.8V to 2.0V is "undefined." This means the counter could increment at 0.8V. It has been my experience that National Instruments TTL will always see 0.8V as a "High." If your noise exceeds 0.8V you will never be able to count accurately.
The problem will be solved when your encoder signal is read cleanly by the 6601. This is why I gave you the URL for US Digital in the previous answer. The circuits they sell can help to clean up the counter signals. You will have to see what works best, since I don't exactly understnad you application. If the noise is very bad, you may wish to use the Encoder to Binary Number circuit. There will be no noise in the reading of a binary number. Since your encoder may run as fast as 8MHz, you must be sure the circuit you choose is also this fast.
The other solution is to eliminate the noise which is causing the counter to trigger falsely. THis can be a very interesting problem to solve. Please look a this NI link:
Field Wiring and Noise Considerations for Analog Signalsv
http://zone.ni.com/devzone/conceptd.nsf/webmain/01F147E156A1BE15862568650057DF15?opendocument
Follow these instructions very carefully.
Also, this book is helpful to explain noise and how one may reduce it.
From Amazon.com you can get Grounding and Shielding Techniques, by Ralph Morrison.
http://www.amazon.com/exec/obidos/ASIN/ 0471245186/104-3492923-2811911
Be very careful how you wire the circuits. Try to use only one ground point.
The worst source of noise can be the motor and drive that spins the encoder. Be particularly careful in wiring this apparatus. A simple solution can be to use an air powered motor insted of an electric motor.
Good luck,
Mike Ross

Similar Messages

Troulbe in measurement quadrature encoder with 6601.

Hi,
We are trying to measure position with 6601. The frequency of quadrature encoder is from 100Hz to 8MHz. Now, we connet the A,B and Z channel directly to counter . Using the example in CVI, we change the filter to 100ns and use x4 mode. It works perfect at low frequency.
The problem is when the frequency of encoder is higher than 2MHz, the accuracy decreases greatly. I'd like to know about following:
1.Can 6601 do the previous task enough? Or I must change to use 6602.
2.If 6601 is available, is there any way to increase measurement accuracy ?(in software or wire connection )

Jimmy,
You would need to specify what type of accuracy you are looking for, which is pretty much dependant on the type of operation you are performing. You could be looking to timestamp your encoder positions or you could also be looking to perform position/angle tracking over time. You could also be performing single point vs. multiple point (buffered) operations. You could mention which one of the CVI examples you are using and that could give an idea of the type of operation you are performing.
The NI-6601 is able to perform quadrature encoder measurements and the only limitations you can have in regards of frequency are the filtering parameters (if you use filtering) and the actual maximum timebase of the board (20 MHz).
Please keep in mind that by ena
bling filtering at 100 ns you are only guaranteeing that pulses with widths of 100 ns or longer are not being filtered out. This limits your encoder phase frequency to around 5 MHz. (Each encoder period has a 50% duty cycle, therefore the pulse duration is half the encoder period). You can refer to the board�s manual for more information on filtering.
We would have to know the following in order to provide further help:
a) Type of operation being performed
b) Specific example you were using
c) Type of accuracy you were looking for
d) Range of accuracy you needed on your measurement
Regards
Alejandro Asenjo
Applications Engineer
National Instruments

Quadrature encoder with a non-NI board

I am attempting use an encoder with a non-NI board (Measurement Computing) and I am unsure how to interface the encoder output from the board with LabView. I have the VIs for the board which allow the board to interface with LabView,. I essentially need a VI to decode the quadrature, the ones in the tutorials were not very helpful or insightful.

Hello Mystery,
Take a look at the section “Velocity and Acceleration Calculations” in this devzone. While the article itself applies to CompactRIO, the equations used in the above section can help you determine how to convert the counter output into a velocity measurement.
Does the counter value increase when you rotate the encoder in one direction and decrease when you rotate in the other direction? This is essentially position measurement. By knowing the number of ticks per revolution as well as the starting position of the encoder, you can determine the current rotation position. For velocity, there is a little more to the measurement. The concept relies on taking a counter measurement in a periodic manner. Then you can use the number of encoder pulses that have occurred over that period of time to calculate velocity. The document I linked about shows how to convert the number of encoder pulses over a fixed period of time into RPM which can be later converted into angular velocity. Hope this helps.
Regards,
Browning G
FlexRIO R&D

Quadrature encoder with PCI-6259 DAQ board (driver for QNX)

where can I find any example for connecting Quadrature Encoders with M Series DAQ Boards ?
The only more or less suitable example I found in nimseries DDK, is
"Count pulses from an external source using an external signal to control
the count direction" (nimseries\Examples\gpctex2.cpp).
But this example is not working correctly with Quadrature Encoders
(encoders with two shifted on 90 degrees phases A&B).
i.e. in case of using this example code I get some extra count while encoder is on vibrant motor
what means enums
typedef enum {
       kG0_Up_DownHardware          = 2,
       kG0_Up_DownHardware_Gate     = 3,
} tG0_Up_Down;
and
typedef enum {
       kG0_Encoder_Counting_ModeId          = 1,
} tId;
in (nimseries\ChipObjects\tTIO.h) ?
What initalization procedure I need to work with Quadrature Encoders?
I have PCI-6259 DAQ device
and I'm writing programm under QNX6 operating system

Hello alexey_3269,
If you want to read a quadrature encoder start with gpctex1.cpp and follow the thread.
I give you my code:
BEGIN CODE
==========
boardGpct->G0_Mode.writeG0_Load_Source_Select(tTIO::tG0_Mode::kG0_Load_Source_SelectLoad_A);
boardGpct->G0_Load_A.writeRegister(InitialCount);
boardGpct->G0_Command.writeG0_Load(1);
boardGpct->G0_Load_B.writeRegister(0);
boardGpct->G0_Load_A.writeRegister(0);
boardGpct->G0_Input_Select.setG0_Source_Select(9); //see above for choices, PFI8=9, 100 kHZ=18
boardGpct->G0_Input_Select.setG0_Source_Polarity(1); //0=CCW, 1=CW
//If using 80 MHz timebase
boardGpct->G0_MSeries_Counting_Mode.writeG0_MSeries_Alternate_Synchronization(1);
boardGpct->G0_MSeries_Counting_Mode.setG0_MSeries_Encoder_Counting_Mode(3); //3 for X4 encoder counting
boardGpct->G0_MSeries_Counting_Mode.flush();
//Enable Input Pins
boardGpct->G0_MSeries_ABZ.setG0_A_Select(9); //PFI8=9,
boardGpct->G0_MSeries_ABZ.setG0_B_Select(21); //PFI10=21
boardGpct->G0_MSeries_ABZ.setG0_Z_Select(10); //PFI9=10
boardGpct->G0_MSeries_ABZ.flush();
boardGpct->G0_Mode.setG0_Gate_Polarity(1); //invert=1
boardGpct->G0_Mode.setG0_Output_Mode(tTIO::tG0_Mode::kG0_Output_ModePulse);
boardGpct->G0_Mode.setG0_Loading_On_Gate(tTIO::tG0_Mode::kG0_Loading_On_GateNo_Reload);
boardGpct->G0_Mode.setG0_Loading_On_TC(tTIO::tG0_Mode::kG0_Loading_On_TCRollover_On_TC);
boardGpct->G0_Mode.setG0_Gating_Mode(tTIO::tG0_Mode::kG0_Gating_ModeLevel_Gating); //kG0_Gating_ModeGating_Disabled
boardGpct->G0_Mode.setG0_Gate_On_Both_Edges(tTIO::tG0_Mode::kG0_Gate_On_Both_EdgesBoth_Edges_Disabled);
boardGpct->G0_Mode.setG0_Trigger_Mode_For_Edge_Gate(tTIO::tG0_Mode::kG0_Trigger_Mode_For_Edge_GateGate_Starts_TC_Stops);
boardGpct->G0_Mode.setG0_Stop_Mode(tTIO::tG0_Mode::kG0_Stop_ModeStop_On_Gate);
boardGpct->G0_Mode.setG0_Counting_Once(tTIO::tG0_Mode::kG0_Counting_OnceNo_HW_Disarm);
boardGpct->G0_Mode.setG0_Reload_Source_Switching(tTIO::tG0_Mode::kG0_Reload_Source_SwitchingAlternate);
boardGpct->G0_Mode.flush();
boardGpct->G0_Command.setG0_Up_Down(tTIO::tG0_Command::kG0_Up_DownHardware); //kG0_Up_DownSoftware_Down
boardGpct->G0_Command.setG0_Bank_Switch_Enable(tTIO::tG0_Command::kG0_Bank_Switch_EnableBank_X);
boardGpct->G0_Command.setG0_Bank_Switch_Mode(tTIO::tG0_Command::kG0_Bank_Switch_ModeGate);
boardGpct->G0_Command.flush();
boardGpct->Interrupt_G0_Enable.setG0_TC_Interrupt_Enable(0);
boardGpct->Interrupt_G0_Enable.setG0_Gate_Interrupt_Enable(0);
boardGpct->Interrupt_G0_Enable.flush();
END CODE
========
I hope this code is appropriate to you.
FV1234

6602 quadrature encoder with c code

I need to implement a quadrature encoder on the 6602 board usinng c language.
I found some good function, for example DAQmxBaseCreateCIAngEncoderChan, but i think this function is only for DaqmxBase,
is there some similar function for Daqmx, or have i to do it myself?
From where can i start?
Thank you in andvance
There are 10 kinds of people. Those who understand binary notation, and those who do not.

Solved my problem.
I installed the daqmx version on CD and it was old.
Now i installed the new version daqmx 9.0 , that i toke from the site.
This version has the function i need DAQmxCreateCIAngEncoderChan,
it compiles , now i have only to attach my encoder.
Thank you lo stesso
Message Edited by blacksocket on 02-08-2010 05:32 AM
There are 10 kinds of people. Those who understand binary notation, and those who do not.

15 T quadrature encoder with NI 9401

Hey,
I have a 15 T encoder with 1024 pulse/rev and I have it hooked to a 9401 daq to measure angular displacement. I was having issues with the signals reaching the threshold value of .8 V for the daq so I ran channels A and B through a bang bang control circuit. Now, the daq reads the signals, but only counts up. I scoped the channels and it looks like the pulses are not 90 degrees out of phase. I removed the channels from the circuit and they are still perfectly in phase. Is there a good way to get labview to add a 90 degree phase delay to only one channel? I'm running a two-channel pulse count with no Z channel.
Thanks a ton,
Wyatt

Problem solved, but now there is noise from the wind tunnel affecting the encoder signal. They are not wired to the same power source though and I'm sure it isn't vibrations from the wind tunnel because the noise occurs even when I drive the motor at 1Hz.

NI 6602 measure quadrature encoder with two signal edge sepearation

Is it possible to improve the position measurement for X4 encoders,
that the measurement starts at start trigger and stops at the stop
trigger signal like the normal two signal edge seperation measurments.
Everything I tried don't works. Does anyone have an idea. Thank You
for Your trouble.

Hello Yong,
You have no wait time within your for loop. This means that the loop will execute as fast as possible, but not at a constant rate. To acheive a more constane rate, try inserting a Wait Time of 1 ms. This will get you a loop with a 1 kHz rate.
How fast is your PWM Signal? It may be that you are missing some two edge measurements while waiting for the loop to iterate.
I suggest merging your error clusters out of the DAQmx Read.vis. Right now, you are just clearing out any errors. Let me know if you start returning any errors once you have done this.
Regards,
Sean C.

Using PCI-6025E with quadrature encoder.

Hi,
i'm presently trying to figure out if i can use the PCI-6025E Card to count up/down with a quadrature encoder with no additionnal hardware. I know my answer lies in a document called "Using Quadrature Encoders with E Series DAQ Boards document " but it is not presently available on the ni website.
Can any1 either confirm me that i can do this or send me the document?
Thank you,
Max

This link seems to confirm that you can
Link
Randall Pursley

Programming quadrature encoder

I'm trying to program a incremental optical encoder with nidaqmx 7.4, with C#, using the PCI-6071e card. I want to measure position, velocity, and acceleration.
As per the "How Do I Use a Quadrature Encoder with My Data Acquisition Board?" document, channel A of the encoder is connected to ctr0_source, channel B is connected to DIO6, and index is connected to ctr1_source.
I'm trying to run the the MeasAngularPositionBuffered_Cont_ExtClk example. However, an exception is thrown when calling myTask.CIChannels.CreateAngularEncoderChannel.
The messagebox says "Selected physical channel does not support the measurement type required by the virtual channel you are creating. Create a channel of measurement type that is supported by the physical channel, or select a physical channel that supports the measurement type"
Also, there is an option in the example program to enable the Z index. How does that program know which channel to read the index pulse?
I'm new at data acqusition, so any other hints regarding optical encoders are appreciated.
Thanks,
Gerry

You also may be able to measure position using the "Count Edges" measurement with an external direction control. This may be enough for your purposes. Just bear in mind that quadrature encoders typically give off noisy signals, so you might have to build an external circuit to clean up the input signals. Let me know if you need more information on doing this with your E Series device.
gus....

Measuring distance using quadrature encoder

I am currently doing a project that requires the positioning and characterization of TV signals. As such, the position of the TV receiver is one important variable that i have to measure. I am required to automate the measurements and data logging using a PC/notebook. I have purchased a 2-channel HEDS-9000 quadrature encoder with 2000 CPR & the HEDS6120 codewheel - both from Avago Tech, to be interfaced with the notebook/PC. My idea is to get a TTL-to-RS232-to-USB converter to interface with the PC, so that i can feed the output from the encoder to the PC. However, i dun have much idea on how I can use LabView to interface the encoder and the PC. Can anyone offer some valuable advice?
Btw, the encoder module consists of 5 pins - Vcc, GND, CH.A, CH.B, with one pin not used.
Thanks !!

Hi,
I think one of the best and reliable options that should meet your needs is a bus-powered USB-M-Series device like the USB-6210.
The USB-6210 is a multifunction data acquisition device with 16 analog inputs, 4 digital inputs, 4 digital outputs and 2 counters. Each of the counters can interface directly to the quadrature encoder signals of your HEDS-9000.
It's very easy to use this device with the NI-DAQmx API for position measurements in LabVIEW. In fact there are some shipping examples that you can use for getting started.
I hope this helps,
Jochen Klier
National Instruments Germany
Message Edited by Jochen on 02-09-2007 09:18 AM

Quadrature encoder counter with 8 channels

Hi,
I need to acquire the signals (A and B) of four quadrature encoders. The signals have a maximum frequency of about 5kHz and should be read out with about 100 Hz. Is there a device that fulfils these requirements? It seems that a frequency of 5kHz is no problem since e.g. the USB-6008 has a counter for frequencies up to 1 MHz. However, I can't find a simple low-cost device that provides several counters. Does anyone know such a device with 4 or 8 counters?
No other analog or digital channels are necessary, but a USB connection and Matlab support would be ideal.
Thanks in advance.

Depending on your definition of low-cost, the 9171+9401 might suit your needs:
4 counters capable of quadrature encoder measurements (the single counter on the 6008 only does simple edge counting).
USB connection.
MATLAB support via the Data Acquisition Toolbox (according to their website).
I don't believe NI currently has any other option that meets these requirements at a lower cost. If USB isn't mandatory, you could also consider the PCIe-6612 which provides 8 counters.
Best Regards,
John Passiak

Quadrature Encoder measurements with PXI-6143 S-Series DAQ

Has anyone used a S-series PXI-6143 DAQ to take encoder position measurements? I believe there are 2 counters available, if you have any examples of how to access and read from these counters it would be greatly appreciated.

Hi Bentup,
Measuring a quadrature encoder on your device is actually going to be a bit different than on an M series device. The STC-2 chip, which is used in the M series, allows for A and B inputs specifically for encoder signals (used in the Angular Encoder task). The original STC-1 chip which is used in E series and most S series boards (including your 6143) does not have these same inputs. Instead, you may must a Count Digital Events task (taking advantage of the up/down line of the counter). The Angular Encoder task is not supported on STC-1 devices.
The article that lab_boy linked earlier actually mentions how to use an encoder with an E series device once you scroll down a bit (here's the link again). This same procedure should apply to your S series--connect the A output of your encoder to the source of the Counter (this is the signal that you are counting). Connect B to the up/down line of the counter (P0.6 and P0.7 for counter 0 and 1 respectively).
The downside with this method is that it is more susceptible to vibrations or noise on the encoder lines. If this is a problem for you, you can look into an external encoder conditioner like the one mentioned in the article. I hope this helps!
Best Regards,
John
John Passiak

Want to get velocity with quadrature encoder

I can count and measure the displacement from the encoder signal with your quadrature encoder example file.
But, can you please advise me know how to implement to get velocity or RPM from that somewhat easily?
Thank you for your help.

Hey Encoder,
You can measure velocity by using a buffered, counting operation. With a buffered operation, the count is latched on the rising/falling edge of the gating signal. Therefore, if you provide a signal to the gate with a known frequency, you will be able to mathmatically determine the frequency of the signal connected to the source.
You can usually use another counter to provide a gating signal with a known frequency. There are example programs that illustrate how to do this.
DAQ-STC: Measuring the Frequency of a TTL Signal (Easy-Level VIs)
http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=B45EACE3DD4756A4E034080020E74861&p_node=DZ52329&p_source=External
Measure a TTL frequency with DAQ-STC or NI-TIO in Visual Basic
http://si
ne.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=B45EACE3D7A756A4E034080020E74861&p_node=DZ52329&p_source=External
I hope this helps.
Regards,
Todd D.
NI Applications Engineer

Can I use the 'Export Signal Property Node' on a quadrature encoder?

Hi,
So I don't know which counter board I'd be using yet for this (it's used in conjunction with a PCI-6280--the PCI-6280's counter inputs are all taken and so I need another board), but assuming this is possible at all in DAQmx I wouldn't mind knowing whether, say, the PCI-6601 (or any other timer board for that matter) could do this. I'm programming this in LabVIEW 2010 by the way.
I want to have a counter which counts the number of pulses on one channel (I'll call this the 'clock' channel) between when another channel goes from low to high (which I'll call the trigger). It's basically a pulse width measurement, but I only care if there are more than n clock pulses between triggers. I need to have a hardware-timed digital signal which goes from low to high if there are ever more than n pulses between trigger changing state from low to high.
What I am planning to do is this:
Wire 'trigger' to the z-input of the quadrature encoder, and set the z-input value to some arbitrary large value such that, at the quadrature encoder counter task's settings, the counter reaches terminal count in n pulses.
Configure the quadrature encoder counter using DAQmx Export Signal Property Node (tutorial I was looking at is here: http://zone.ni.com/devzone/cda/tut/p/id/5387 ) to toggle a digital channel ('counter event output') from low to high if the counter reaches terminal count (ie, if the encoder reads n pulses).
If the encoder ever reads n pulses on 'clock' between two rising pulses on 'trigger', it sets counter event output high.
Is this possible? Reading through the manual of M series PCI-62xx devices, the index pulse loads the counter with a particular value so it seems like you could conceivably set the counter to the terminal count if you wanted. My only real problem is whether DAQmx Export Signal Property Node works on all counter tasks or just on edge counting tasks.
Thanks in advance for your help. If this isn't possible, I can reply with more details on the problem this is supposed to solve so that you can help me figure out an alternate method.
Solved!
Go to Solution.

There is probably a way to do it, but it it may be easier to use an X-series board for the job. They support a new counter capability for count reset on a digital edge without needing to be configured in encoder position mode. I am not sure exactly how that feature's been implemented however, so maybe it won't make things easier after all.
The plan based on the hoped-for behavior:
1. Configure an X-series counter for pulse generation based on "ticks" of your clock channel.
2. Set both initial delay and low time to the critical # of ticks.
3. Configure for count reset on a digital edge (if possible in pulse generation mode)
4. Configure the count reset value to be the critical # (or possibly 1 less, if possible in pulse generation mode)
5. If you want the output to remain high indefinitely, configure the counter task to use its own output as a
pause trigger, and pause while high.
The way pulse generation works is to preload a # of "low time" ticks into the count register. Then every source edge will decrement the count. When the count reaches terminal count (0), the counter's output is toggled (or can be configured to pulse). The register is then loaded with the # of "high time" ticks and the process continues.
You would be perpetually interrupting the count-down process as long as you got your triggers in time. The count would keep getting reset to the # of low counts, keep decrementing toward 0 without reaching it, and so on. If ever you did reach 0, the output state would toggle high, then the high state would prevent subsequent clock signals from decrementing the count.
You can conceivably do a similar thing with a 6601, but I'm pretty sure you'd need 2 counters working together to get it working.
-Kevin P

How to calibrate Quadrature Encoder signal

I have PCI-6601 and CB68-LP connector. How can I use these to interpret quadrature signals coming off an optical encoder (to sense the angular position of an-observatory dome). The encoder is 16-bit(don't know what this means in terms of PPR). I want to have a display in Labview that will show me the position of the dome in a fraction of 360 degrees with some reference(true north?), the dome rotation controlled by a three way switch(clockwise-off-anti-clockwise). I don't have much experience with labview and any help will be appreciated.

If the encoder is 16 bit then it would seem that: -
360/65536 = 0.0054931640625° or there abouts.
You can break the project down into two halves nicely.
1) Hardware interfacing.
2) Software read out.
The hardware interfacing means two basic things:
1.1 What is the encoding technique
1.2 How are the signals conditioned for output to an external device.
The software is classic:
2.1 Input
2.2 Process
2.3 Output
The optical encoder could be one of a few types and you need to understand both the signalling / interface and the coding technique to progress further. A good start will be the manufacturers data sheet for the product. Contact the manufacturer.
Once you understand the coding technique you will then know if the unit is absolute or relati
ve. This will then allow you to determine how you can point to true north (easily with an absolute encoder, it always tells you exactly where it is).
If it is a classic quadrature encoder then the relative phase of the reference and movement signals gives you direction. Counting transitions gives you realtive movement. But if the power went off on the PC. you don't know where you are unless you go to a home position! That could be 359° round !!!
Good Luck

Troulbe in measuremen​t quadrature encoder with 6601

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Troulbe in measurement quadrature encoder with 6601