Connecting PMT to read voltage vs. time

[Solis]

Hello,

I am new hear to the labview forums and was wondering if you guys might be able to help me out.  I am an undergraduate student working on an LED-induced fluorescence detector.

A little bit about the system:

I'm using a blue high powered LED focused on a 25x microscope objective onto a capillary tube.  The fluorescence in the tube will be captured by a 10x microscope objective at 90 degrees to the other objective, which will then be filtered and captured by a PMT (Hamamatsu h7732-10)

This PMT will also be hooked up to an amplifier (Hamamatsu C6438-01)

My goal is to hook the PMT up to a computer with Labview software and read voltage vs. time for the fluorescence.  If possible I also wanted to hook the power supply up to the computer so we would be able to control the voltage through Labview too.  

In all honesty, I've been playing around with labview for a couple weeks and still seem quite clueless as to where to start.  My professor hasn't given me much to work with either since he doesn't really know the Labview software.

I was wondering if you guys might be able to help me out in any way or send me in the right direction.  These forums seem very helpful, and any help will be much appreciated.  Let me know if you need any more information about what I'm doing.

Thanks again!

-Greg

[srikrishnaNF]

Hi solis,

  Just now i gone through the data sheet of the PMT,it has got BNC output.So what i think is that you need a data acquisition cardw ith some what less sampling rate to acquire the data generated by PMT.Once the data is acquired in labview ,you have plenty of ways to present the data.

To have an of labview data acquisition please visit www.ni.com/dataacquisiton.

Thanks and regards,

srikrishnaNF

[Solis]

Ah yes, I forgot to mention, I do have a DAQ, specifically usb-6009

Is this sufficient for connecting my PMT, even though it will have a signal output with a BNC cable?  Can I strip the other end of the BNC cable and put the wires in the usb-6009?

So the best way to start using labview would just be to connect the pmt to the DAQ and start setting it up from there?

Thanks for the help  

[falkpl]

Since this is a school project I cant give too much away but here is where you can start.

1.  Open MAX rtclick under devices and interface on your 6009 and sewlect test panels, you can get the analog input tested there, ie if all is wired up correct the analog channel will scale with the light entering the PMT.

2.  Once voltage is verified, try to repete this with daq assistant.  You can also explore the analog input continious buffered sampling examples to see what the code should look like.  You should beable to graph the incomming signal now.  Play with scales to see if you can get the correct counts from the PMT.

Get this working first, then you can add many extras.

 Good luck,

[Solis]

This isn't part of a school project, it's part of my undergraduate research group.  It's completely fine to get as much help as I want since the graduate students experienced in this program are kind of backed up at the moment, which is why i'm here on the forums for help.

I forgot to mention I am using a mac with Labview 8.6 and DAQmx base 3.2.  This is the most recent version that is compatible for MAC that will work for the usb-6009 correct?

Anyways, I'm slowly getting to know daqmx base a little better but still need much help as to how to create a graph that reads voltage vs. time in labview.

Thanks again 

[Paul Henning]

I'm working on a similar task myself: fiber optic fluorescence with H6779 PMT, LED excitation, and USB-6009 DAQ.

You can use one of the analog outputs on the USB-DAQ device to control the gain of the detector. The Hamamatsu datasheet should contain the information on how to connect the VRef and VControl to control the detector gain. It does work, but I now use a potentiometer for simplicity with our setup.

It's worth pointing out that PMTs can be operated in two different modes: counting and analog. At low light levels and high gain, the detector will output pulses (~10-100 mV high, 5 ns wide) corresponding to single photons. The single photon pulses can be monitored with a 100 MHz or faster oscilloscope and can be easily counted with the approriate instrument. At higher light levels, the photon pulses will overlap leading to counting errors. However, the output current (irrespective of waveform) of the detector can be measured. So, the USB-6009 does not have the time resolution to perform photon counting, but it should work for measuring the photocurrent. But, if the signal intensity is too low, the photocurrent may not be within range of the 6009 capabilities.

AFAIK, everything should work fine. I'm just recently switched from a photodiode to a PMT, and will post my results.