Synchronize 2 USB-DAQ devices, Analog IN, Frequency IN, Digitally triggered

Hello,
I want to perform the following measurement on two USB-6211 devices, LV 2012:
I need to
1) read (cont.) all 16 analog input channels of Dev1
2) read( cont.) 2 analog input channels of Dev2
3) perform a frequency measurement with Dev2
4) synchronize 1-3
5) start the Measurements with a trigger (light barrier)
1) and 2) are not the problem. Also synchronizing them is fine. But I am not sure if my attempt to synchronize all this with the freq measurement, as this is done over a certain period of time. So, as I understand, when I select the method "high frequency with 2 counters" I can specify the measuring time. So I think I need to tell labview somehow which point of time of this span shall be synchronized with the analog input.
I attached a first try and am thankful for any hints.
Thanks, Jack
Attachments:
test.vi ‏42 KB

The basic problem here is conceptual. What does it mean to "synchronize" a time domain measurement with a frequency domain measurement? You can certainly can (and should) identify the set of time domain measurements that went into the calculation of the frequency measurement, but that's about the thinnest you will be able to slice this bologna.
Having said that, I can't look at your code right now but I assume you are reading data in blocks from the DAQ. You could perform the measurement for each block you read. That would naturally associate the measurement with the data it was based on.
Mike...
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Attachments:
shimadzu-lc-6a-hplc-pump-service-manual-eng.pdf ‏985 KB

I highly recommend you look up your local NI representative and have a nice sit down with them. They can go over your requirements and give you really good advice on which device to get.
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Hi Nasib,
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dianageorge a écrit :
I have to Run Multiple Instances of a LabVIEW Executable Simultaneously. Is it possible to access the same DAQ ni usB-6289 device for all of the LabVIEW instance?
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Attachments:
daqmxbase.JPG ‏59 KB

Actually it is not the easiest to use the full version of daqmx is easier, It is also very easy to set this up in MAX (measurement and automation explorer) What version of labview are you using. have you made sure that the device is recognised in MAX and that the device number is correct. i have a couple of 6008 and have run them alot without any trouble so it must be the way you have things setup. Could you post a section of the code that gives you the error. also try running each device in max with the test panels for each one and see if it works there.
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I've been looking at the example Sim Phone.vi that comes with labview and would like to generate similar tones out of our usb 6008 device. I can get a very faint sound out of our usb 6008 using the example Gen Multi Volt Updates-SW Timed.vi Does anyone know the best way to alter Sim Phone.vi to have the sound come out of the Analog output of our usb 6008 device. ( I have a small speaker connected to the Analog out on our USB 6008)
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Attachments:
Gen Mult Volt Updates-SW Timed.vi ‏78 KB

Hi sal2,
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Solved!
Go to Solution.

Another question is in continuous mode, NI DAQmx uses Samples per channel to determine the buffer size. But according to the website you specified, it says if the acquisition is continuous (sample mode on the DAQmx Timing.vi is set to Continuous Samples), NI-DAQmx will allocate a buffer according to the following table. And for sample rate between 100 - 10,000 S/s, the buffer size is 10 kS. So if I set the sample rate to be 5000 S/s, and set the Samples per channel to be 20000, then what exactly the buffer size is? 20 kS or 10 kS?
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Capture.PNG ‏76 KB
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AnkitG wrote:
Jeff·Þ·Bohrer wrote:
Why would you create an Task with an analog output? its a Digital line you want to drive! and, just create it in the project.
Hi Jeff,
thanks but I couldnt understand , what you meant by create in project? Can you please explain. should I create digital line but I am still getting the same error.
Creating DAQmx items in Project Explorer saves the DAQmx object properties as part of the *.lvproj file. This can be very useful when the Task configuration does not change in the built application and you seldom want to use the task elsewhere. If you want to make minor tweaks to configuration of the run-time app there is even a human readable text file in the build output where properties like scale offsets, timing rates or ranges can be modified without redeploying a new app.
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Not receiving any signal input with LabVIEW SE, USB DAQ board

Hello all, good afternoon.
I am having a little trouble with my DAQ device, I hope that someone will be able to help me.
I'm plugging a BNC pH sensor to a NI USB 6251 M-series board, to try and obtain the electrical response of that particular sensor, measuring the voltage output for each buffer solution (pH 4 and 7). Have 9.2.3 mx (lastest) drivers.
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Good afternoon.
Yes I have tried all of that. The board responds very well when a flat 5V DC voltage is fed into a channel.
However after much investigation I believe to have found the problem yesterday, it probably has to do with the operational amplifiers I was using. The input bias current was in the magnitude of nanoAmps, while for pH measurements an IBC of picoAmps or less is necessary due to the high impedance of the sensor. This was causing a drift of over 100 mV on my output which is about 2 pH and thus unnacceptable (even though I had the Bias resistors at the input to ground, like suggested in the NI tutorials, but apparently they were not enough to compensate for the high IBC).
In the lab all available op-amps suffer from this, even Instrumentation op-amps like AMP04 from Analog Devices. I still haven't had a chance to acquire new op-amps with the necessary IBC but hopefully it will do the trick. Makes sense since I checked the datasheets for every op-amp in the lab, and they all had IBC around 400 nanoAmps (and none of them worked), while every single op-amp for every pH meter circuit I found have IBC's of pico/femtoAmps.
The sensor I'm using is from AquaMedic, I'm not sure what the model is, but it's a cheap plastic sensor that comes bundled with their pH Computers.
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Synchronize 2 USB-DAQ devices, Analog IN, Frequency IN, Digitally triggered

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