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Help with photon counter data acquisition using LabView 12

June 27, 2013, 1:19 pm
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Hey All,

 

Chemistry graduate student here brand new to LabView and looking for some help to move in the right direction.  I am looking for help with connecting my PerkinElmer SPCM-AQR-14 (now owned by Excelitas Technologies) photon counter to LabView 12 for trace-fluorescence data acquisition.  I simply want to be able to acquire # of photon counts vs. time.  I currently have installed a PCI-6601 and use a BNC-2121 to connect the BNC output from the detector.  The detector has a digital TTL pulse output with 30 ns pulse width, and in contacting tech support about this, I was told that this pulse width was too short to be consistently detected by the 6601, but can still go ahead and give it a try.  Basically, if anyone is familiar with how to get started with this setup, ANY help would be greatly appreciated.  As I said I am brand new to LabView and am currently spending all of my free time reading through manuals and help files. 

 

Please let me know if you need any sort of additional information from me to understand what I am doing.

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Digital Frequency Measurement for cRIO

July 2, 2013, 12:25 pm
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Hi,

 

I'm new to LabView, and I'm having problems setting up a VI for frequency measurement. Any tips would be greatly appreciated!

 

Task: I am using a cRIO with a digital I/O module (NI 9403). My goal is to connect the sensor that I am using (a MAXIM 6576 temperature sensor with period/frequency output in the form of a square wave) to the cRIO and have a VI measure and output its current frequency or period. 

 

I've tried working with the Count and Period.vi, but when I tried to compile I found out the 9403 module does not support SCTL. I also looked at a thread that was posted in 2009 (http://forums.ni.com/t5/Counter-Timer/beginner-stuff-cRIO-digital-frequency-measurement/td-p/826656/highlight/true) that discussed a similar problem, but when I tried using the Host VI I got the multiple error messages saying "Function not supported in current target". This happened even when I tried using the original Count and Period (Host).vi with no modifications (but the original Count and Period (FPGA).vi works just fine). 

 

I don't know how to approach this problem - should I be using FPGA or Scan Interface mode? Are there any basic examples of frequency measurement or digital counters that do not involve NI data acquisition devices? For a basic counter, how would you set up the VI so that it could measure the period or frequency based on the counter values? 

 

Thanks a lot for your help!

 

Andrea

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Generating 2 clocks with different phase using PXIe-6674T ??

July 3, 2013, 4:33 am
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Hi,

 

is it possible to generate 2 clocks (same frequency) with different phase using PXIe-6674T ?

 

regards,

Yan.

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Is it possible to store ultrasonic sensor data till get to the next required target?

July 7, 2013, 10:03 pm
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Hi,

 

I have a proximity ultrasonic sensor used to control a weeding device. I am using the sensor to detect the differences of plant heights. Plants are weeds and crops, I want basically to kill weeds and avoid damaging to crops by the device. The crops are higher that weeds, so I am using LabVIEW with USB DAQ 1208FS to compare the different heights. My sensor is located in front of the device in about 20 inches. When it starts reading the first plant (weed) the device will act immediately and kill it. When it gets to the second plant (crop), the device will act on the first plant which means skip some weeds as the sensor read crop. This way I might kill crops along with weeds or skip weeds. Is it possible to store or delay the sensor data till the weeding device get to the required target? Thanks!

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Is it possible to connect PCI-6221/BNC-2110 to encoder signals A,B and /A,/B?

July 9, 2013, 10:38 am
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Hi!

 

I've connected the encoder with BNC-2110 but only A,B signals. Is it possible to wire /A,/B signals to BNC-2110?

 

Thanks for Yours help.

 

 

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PWM measurement with NI 9411 is never zero

July 10, 2013, 7:38 pm
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Hi folks,

 

I am using the NI9411 DI module on a cRIO 9074 to measure a 1 kHz PWM signal.

I created an empty project, set the mode of the module to "counter" "pulse width measurement" "High pulse" and "disabled" input filter.

For taking a first look at the measured values i used the NI distributed system manager.

At the beginning the measured values seem right, they are somehow multiplied with 10 but i can easily correct that with a normal division by ten.

The problem is, if i pull the plug which connects the NI9411 to the pwm generator, the duty cycle never goes to zero but stays somewhere between.

For example if the duty cycle is 510 (that is supposed to be 51) and i pull the plug it goes to 230 and stays there. If i repeat the step of plug-in and out, the duty cycle sometimes drops to 1.25 and sometimes to 70.

The values seem random and the counter stays at this value the whole time until i plug it back in.

For my application the module has to see the "missing" pwm if the plug is removed.

 

How can this be and how can i solve this problem?

 

Thanks

 

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Is it possible to synchronize two NI USB-9162 chassis?

July 11, 2013, 7:59 am
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First of all is this question in the right location? Or should I post it to signal conditioning? Anyways I am attempting to collect voltage differentials using two NI USB-9162 Chassis, one with a NI 9215 module and the other with NI 9219 module and i am getting wierd results when I write the measurment ot a file. Any hellp would be greatly appreciated!

 

Thanks

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Can I use the the measured time between the first count and the last count in a fixed time window in order to increase the accuracy of a quadrature velocity measurement?

July 12, 2013, 2:24 pm
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I am measuring velocity using a linear encoder. Resolution is 40microns, sample frequency is 1MHz and the real velocity is oscillatory in nature with an amplitude of 200 to 400 mm/s with a freq of about 1Hz. We use a 5ms fixed time window to measure velocity. The quanization error for this is 8mm/s. Can I get rid of the quatization error by somehow measuring the exact time from the first pulse to the last pulse in the measurement window?

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PCIe-6321 counter failing at high frequency

July 14, 2013, 10:35 pm
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I'm trying to use the counter on the 6321 as a frequency divider that takes an 80 MHz sin wave input and generates a 10 MHz square wave output by digitizing the output of a 50 ohm device on PFI0.  The specifications to for my board list a counter "Max Source Frequency" of 100 MHz, leading me to believe that 80 MHz should be possible.  However, in my experimenting while the counter based divider works very well at lower frequencies, it fails at about 35 MHz by missing edges.  The result is an  unstable output frequency that bounces between 8:1 division, 9:1, 10:1... depending on how many  edges are missed.

 

To explore this problem further, I swapped out my 2 meter 68-pin VHDCI for a 1 meter and plugged my function generator into the break out board with a < 30 cm cable, thinking that perhaps impedance mismatch was an issue.  However, even with < 1.5 m,  the device still works at 30 MHz and fails at 35 MHz.  This suggests to me that impedance mismatch is not the problem, as the maximum frequency was unchanged even though the cable length was nearly halved.   

 

Is there something else I'm missing?  Is there a faster interface than PFI?  Or someway to 50 ohm terminate the device? 

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why does error 200279 occur at high speeds only?

July 18, 2013, 9:24 pm
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I am using a VI very much like the one attached here, and as my motor speeds up and the period value decreases, the vi fails, and error 200279 shows up as displayed in the attached 2 jpg images. This VI is reading the period value of an encoder by rising edges.  The error does not show up at low speeds, only high speeds.  Hardware is wired through USB ports on PC.  Using Labview 2012 and Windows 7.

 

Do I need to specify the samples per channel for the READ in the case structure to eliminate this error?  The error only occurs when the period gets quite short, e.g. 9ms or so.  At higher period values (slower motor speeds) the error does not appear.  I am using the counters built into the cDAQ9174 chassis  and the NI 9401 module to read the period values of my encoder.  What is happening at high speeds to cause this error?  I thought that the setting on the DAQ Timing VI required that 16 periods are read every iteration, so, why is it saying that it is trying to read samples that are no longer available?

 

Also, is the "Append Array" building up a large array that is being carried in the SHIFT REGISTER and causing things to slow down?  There are a huge number of periods occuring with an encoder at 120 ticks/revolution.  should I try to keep this array truncated or something to reduce the size of the data being handled for each iteration?  Can this large array be causing the 200279 error?

 

Thanks,

Dave

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NI USB 6008 AI acquisition and DO pulse genereation

July 19, 2013, 6:15 pm
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Dear LabVIEW users,

 

Greetings for everyone. I am a beginner of LabVIEW and I have a problem, which I have solved partially. I would really appreciate your help and suggestions as I searched for days without any luck. The problem is as following:

 

I am acquiring AI voltage (continous) from 4-8 accelerometers. At the same time, I am sending a digital output signal each time when the sample rate is clicked (i.e. 1000, 2000, 3000, .... if sampling rate is 1000). In other words, trying to send a digital output signal (at some frequency 'n' Hz) at regular 1 second interval (according to hardware level). So that the digital output signal will blink an LED at every one second. Further, I need to write the AI (voltage) signals, and LED blink PC (software) timestamps separately. All the above said steps are followed in my .vi program but the real hardware/software level operations are killing my timestamps. In other words each LED blink timestamps are not accurate when I use LabVIEW measurement file express VI (difference is not atleast to the third decimal place). In addition, the timestamping is somewhat OK when I disable the LVM file write VI. Onemore thing I noticed is that, physically LED blinks every two second once, I suspect this is due to the shift register and loop delay of second. Is there a way to control the blink speed (i.e. boolean state has to change at every 500ms without delaying the inner while loop).

 

Results and observations:

LabVIEW 2011 .vi, timestamp files with and without LVM file generator (express VI) are all attached. Please note that there is a considerable amount of drift in consecutive timestamps when LVM file generator is used, on the other hand there is 0.001 ms drift when LVM file generator is not used. The reason for PC timestamps are to roughtly align different measurements or observations or events in global time scale.

 

Please give me any suggestions or help me to make it atleast accurate for milliseconds within the witten VI. Lastly, is there any relatively inexpensive USB DAQ module which can send a pulse to directly from pulse channel to digital output channels when sample rate of 'n' Hz is achieved by hardware level which could be every accurate, so that software delay is fully minimized. Although there are highly sophistiated hardwares from NI, but our goal of this project is to build and test cost effective system.

 

Thank you and I really appreciate your inavluable time and effort. Have a great weekend!

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NI get the data from very Old Frequency Counter

August 5, 2013, 6:35 pm
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Dear all

 

My project need to get the data from very old Frequency Counter. ( See in picture )

 

It is don't have the output port.

 

My question

1. Have the method or buy some Equipment for get the data from NI?

2. Advise new device for replace the old, can get the data and not expensive?

 

Please advise to me

 

Frequency Counter.PNG

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can I use two chasses and two 9401s for more counting channels?

August 12, 2013, 6:30 am
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Hi,

 

I am currently using cDAQ9174 and NI 9401 and the four counters in the chassis to measure the periods of 4 separate (simultaneous) encoders in a vi.  All four encoders are running at the same time, and the vi measures them all in a single execution; not truly simultaneously, but, within the timing of a WHILE loop.  Actually, I suppose it measures the periods in a serial fashion.

 

I want to add more encoders to my hardware system, and measure their periods within the same vi.  So, can I add another chassis and another 9401, and measure periods of up to 8 encoders this way within the same vi on the same PC?  Will the vi recognize more counters than a single chassis has?

 

Will I face new errors with lots of encoders?

 

Thanks,

Dave

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program in c to read quadrature encoder didn't work (NI 6220)

August 13, 2013, 1:23 am
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Hello,

I have a NI-6220 and I connect quadrature encoder to it . Then I use Measurement & Automation program to read the encoder and it works well.

the problem when I use the c++ program it doesn't work and demonistrate arandom fixed value.

in attached files the code which I used .

I'm waiting for your reply.

 

Best Regards,

Alaa Mohammed Abd Elmoaty Khalifa. 

Egypt-Japan University for Science and Technology (E-JUST).
M.Sc. Graduate Student.
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Counting edges within a period

August 13, 2013, 1:56 pm
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Hello,

 

I'm still fairly new to labview and so I could use some help on something I'm working on.

 

I need to measure two things from an encoder, the RPM, which I can easily do via the index; and the number of edges on the A channel between two index pulses.

 

I would like to use the index to trigger the counter to begin counting edges on the A channel, and then the next index to end the counting. This program will essentially verify the RPM of the encoder given a base speed, and it will verify the correct resolution of the encoder.

 

I am using an NI6602 counter card and I need to be able to configure multiple encoders onto it which is why I'm only using the index and channel A.

 

Thank you,

Jason

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Pulse train generation issue-PCIe-6320

August 15, 2013, 4:53 am
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Hello all..

 Im using PCIe-6320 x series daq to generate pulse train.I have gone through the examples found in the labview to generate digital pulses.Provided vi runs without any error,but i couldnt find any pulse output in my ctr0 pin.Is there any specific connection to be made to check the output?

 

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Not recognizing 2 seperate 9401 modules

August 15, 2013, 5:30 am
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I am attempting to run 7 counter/timer loops off of 2 9401 modules within a CompactDAQ chassis (slot 2 and 5) and continually get the error code of 200371. After a bit of digging we found that in DaqMx the 2 seperate modules were not distinguished with such that Mod2/ctrl0 was just _ctrl0  and Mod5/ctrl0 was also identified as just _crtl0 so simulataneous counter timer loops couldn't be run since they are treated as the same line. Anyone ever encounter this? My intuition thinks its a driver issue but I am not sure what else it might be.

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3A Counter

August 16, 2013, 9:05 am
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Anyone have any low cost/simple solutions to count the contact closure of a microswitch with 3A, 28VDC running through it?  This is for a life cycle test to test the life of the microswitch. 

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Frquency & Duty cycle Value changes- every time

August 19, 2013, 7:26 am
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Hello all

 im using pcie 6320 to measure the frequency and the duty cycle of a signal.i have attached my vi & the data measured for reference.The values highlighted in red ,is my actual frequency and duty cycle but values changes for every 1 sec.Please correct me if i have any mistake.

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Get more resolution (digit) from agilent 5313xA read measurement

August 21, 2013, 8:14 am
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Dear all

 

I am working with LabVIEW 12 and Agilent 53132a (Universal Counter).
I am using Agilent frequency counter to monitor frequency of my devices. I use Labview and GPIB to record my data and for that I use a driver downloaded from NI.

I found data read from read measurement.vi only 9 digit.

I want all data that reading from Agilent 53132a. What I can do?

 

Best Regards

Sermsak

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