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I want to choose the right USB DAQ device for my application

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Let me share the .exe file I am using for my application i.e. Temperature Controller for QCL. It is available at following URL:

 

http://www.teamwavelength.com/support/software.php?page=datasheets&view=temperaturecontrollers

 

The temperature Controller I am using is PTC 10 K-CH. I have got NI USB 6351 DAQ Card. I tried to interface it between PC and PTC 10 K-CH, but couldn't get the desired results.(no accurate monitoring/control of temperature for driving the LASER Source). Because it is a .exe file I couldn't find how code is working as well. Thus though the program runs without any errors, I am unable to figure out why it is not showing proper temperature values.Manual for the same Temp.Controller is available on the website of Wavelength Electronics.

 

I would like to know whether NI USB 6351 is suitable for PTC 10 K-CH? If yes, what common errors I must me making while interfacing the same with LabVIEW(as I am beginner)? Any help is appreciated.

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Hi DEV_DS,

 

It looks like you'll just need 2 AI channels, 1 AO channel, and 1 DO line.  Glancing over the datasheet, I don't see any reason that the USB-6351 shouldn't work with the PTC10K-CH.

 

Can you share with us a screenshot of the DAQ Channels tab configuration, a screenshot of your expanded Devices and Interfaces list in NI MAX, and a description of the physical wiring connections that you've made in hardware?

 

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Hello Kyle B,

 

I had chosen all the ports as suggested in your previous post and also the wiring was proper. Only thing, I was entering the Thermistor details in the VI program as Custom Thermistor data(as seen in Sensor tab of PTC LabVIEW interface provided by Wavelength Electronics) and there was zero voltage generated at the setpoint temperature channel of USB 6350(in my case port ao0). 

 

I found that thermistor R/T values are almost similar to that of 10K standard thermistor. Therefore I selected  the same thermistor from drop down menu available in Sensor Tab and surprisingly, it worked(proper voltage is getting generated at desired output pin of USB 6350). So my preliminary observation is, Custom settings are not working properly for this .exe file.

Please correct me if  I am failing to understand something.

 

I appreciate time taken by you to guide me. Thanks a lot. 

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Please read USB 6350 as USB 6351 in the above post..It was done by mistake....

 

Also, now, I am looking to monitor and control the Current Driver for Laser (QCL 1000) using NI USB 6350. Related link is mentioned below:

 

http://www.teamwavelength.com/products/product.php?part=178&view=overview#tabs

 

Any help regarding the same is welcome. I hope, USB 6351 is ideal for this interfacing. One doubt I am having is, in datasheet for QCL 100 current driver (http://www.teamwavelength.com/downloads/datasheets/qclseries.pdf), on page 14, across the analog input terminals, it is shown that AC signal is to be given. I didn't get it, can anyone justify the same? 

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I don't see indication that the source must provide an AC signal -- and I would have guessed anyway that the Analog Input lines require a DC signal.  That said, it would probably be wise to consult with Wavelength support on the topic.

 

Based on my understanding of the datasheet (after a quick once-over), the 6351 should be a good fit for use with this device, as well.

 

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For a change, I will be using QCL 2000 Current driver of Wavelength Electronics in my application. Can I get help about interfacing it with NI USB 6351? as mentioned in manual available at following link

 

http://www.teamwavelength.com/downloads/datasheets/qclseries.pdf#page=1

 

I opened the QCL driver case and made the Remote control active. But I caouldn't figure out how many digital/analog ports I have to use. I would appreciate the help regarding the connectons of QCL2000 with USB 6351.  Thanks in advance.

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If you look at Figure 2 of the QCL manual, you can see the available inputs and outputs, some of which appear to be optional.

 

It looks like there are two digital inputs and three status outputs. From the descriptions and specifications these seem to be based on 12 V logic and may not be compatible with the 3.3 V or 5 V logic of most DAQ devices.  The monitor outputs have 0-5 V ranges and can be measured by analog input lines.

 

The analog input has a 0 to 5 V range with 1000 ohm input impedance. Make sure the analog output can drive 5 mA. Some DAQ devices have lower current limits than that.

 

Another consideration is glitches on the analog output line. All AO devices generate such glitches when the digital inputs switch. Those glitches might be large enough to destroy the laser.  A low pass fllter can reduce the amplitude of the glitches but how effective a filter may be depends on the control bandwidth you will need. If you use an active filter built from op amps, they should be able to drive the analog input of the QCL 2000.  Do your testing with silicon diodes of suitable current rating until you are sure everything is working well so that you do not destroy expensive lasers. Also watch for power-on behavior of all the devices. Make sure the power and enable control lines keep the device disabled until all power supplies are on, the DAQ device is powered on, and the software has initalized all inputs and outputs of the DAQ device.  Failure to do so may result in smoke, gnashing of teeth, and a large bill for replacing burned out parts!

 

I have used earlier models of Wavelength temperature and current controllers. Be careful. It is not difficult to damage or destroy the devices. Your budget may not like that! Their evaluation boards are very useful for getting systems up and running.  

 

Lynn

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