external aquisition rate

[ProgChemist]

Hello all,

I am trying to update a very old spectrometer to a digital interface. The signals coming from the instrument consist of two signals. One, is a constant analog pulse--which starts at a reference frequency and then every pulse counts as another nanometer or wavenumber. The other signal varies from 0 to 100mV and represents the intensity (of the y-axis) at each respective wavenumber.

Do I need to use a program which controls my aquisition rate externally? From the constant analog pulse sequence? 

I'm also assuming I need to use a PWM program to interpret the analog signal in a digital fashion and then plot it in a waveform?

Can anyone tell me if I am on the right track?

How to integrate the two signals in one program? Examples?

Please help.....Labview newbie.

[pflores]

What is the make and model of the spectrometer? What Data Aquisition hardware do you have?

It sounds to me like you will have to aquire these two analog inputs and do some processing in software. We can be sure of this with a manual or more detailed description of these 2 signals.

A PWM shouldn't be needed as long as you can acuire analog signals.

Here is a great resource for starting with DAQmx (Data Acquisition drivers).

[ProgChemist]

Hello,

I'll get back with you about the make and model of the spectrometer. I think its a SPEX Raman spectrometer. I want to say an early 70's model. It is a very old model and ran on a sliding chart recorder until the motor burnt out on it. 

The DAQ device # is BNC-2110. Do I find my board #, listed under my "devices" in MAX?

 I will ask about the manual, but I'm pretty sure its MIA.

I may have to measure the two signals with an oscilloscope.

Yes, someone talked to me about PWM and I don't think it should apply.

What about a three component cluster centered program? Where X(0) is user inputted, delta X is a function of the constant pulse (moving a nanaometer each pulse), and the third component of the cluster is the other analog signal--where the 0 to 100mV range determines the intensity for each nanometer. And the cluster would be outputted to a waveform graph? Could I design a program where I sample the variable analog signal as a function of each constant pulse?

Does this sound plausable? I'm a little weary about the processing of the signals.

Thanks for the DAQmx resource. 

Regards,

Frustrated Chemist.

[CharlesD]

Hey,

First, the BNC 2110 is simply a terminal block and prolly won't show up under DAQmx Devices.  You likely have an M-Series Device (62xx) or E-Series Device (60xx) that will connect to this terminal block and you will see that device in MAX. 

What you can do is synchronize a counter (reads digital pulse -PWM) and an Analog input.  This will ensure that each time you get a count from the counter you get the corresponding voltage from the analog input.  (Make sure to use a buffered counter acquisition and use the same sample clock for the analog input and Event counter measurement.  If you have the number of pulses that have passed and the voltage of the analog signal at sampled at the same time as the even count you should be able to develop the program to interpret thatinformation and correlate it back to meaningful information. 

I think you are on the right track and you should be able to get this giong. 

[ProgChemist]

Yes, this is exactly the type of design I am looking for.

My only problem is how to make the PWM/counter component. This is the programming I have been struggling with.

Thank you. 

[CharlesD]

Which board do you have?  If you have an E-Series board (60xx) or M-Series (62xx) Card that connects to that BNC-2110 than there should be two counters on that board. 

Those counter can be programed easily as shown in some of the example programs that ship with labview.  You can find these examples here:

1. open LabVIEW--> Help>>Find Examples>>Hardware Input and output>>DAQmx>>Counter Measurements>>Event Counting>>Count Digital Events 

2.Or navigate to (....Program Files\National Instruments\LabVIEW 8.6\examples\DAQmx\Counter\Count Digital Events). 

Inside either folder you will find an example called Count Digitl Events - Buffered - Continuous-Ext Clk.vi

[ProgChemist]

I have both PCI-6251 and PCI-6220 boards. Its the PWM component I need the most assistance with.

[ProgChemist]

Ok, here is my work in progress.

How  do I synchronize the counter and the sampling of the analog signal?

I'm still learning the ins and outs of clusters, how do I have to alter my variables in the clusters so I can output both an array and a graph? 

[ProgChemist]

Ok, so disregard the last VI.

This one makes much more sense, but I know the wiring is still off.

Suggestions? 

[ProgChemist]

Right,

Here is the actual VI.