Constant output in physical channel causing headache

[ndlapointe]

Hi,

I've been using a microscope who runs on LabView for some time now and I recently installed a subVI to control a Sutter ROE-200 moving platform. Since then, I've noticed a constant signal in every physical channel (see picture below) by using an oscilloscope.  I need to use a PMT detector to measure very low light intensity and the background signal is often higher than the one resulting from a photon. I've measured the frequency of this signal to be 40 KHz. 

Is there any way to monitor in real time what is the signal passing through the channels, and to reset or modify it?

Thank you!

[M.J]

Hi ndlapointe,

I think software Signal Processing with Filters will help you move forward.

Below is a link to a video that discusses how to use the Filter Express VI.

http://www.ni.com/academic/students/learn-labview/signal-processing/

[Dennis_Knutson]

Every channel of what? A DAQ card?

[zayer]

what is your subvi? Can you sent to me? I also try to use labview to control ROE 200, but I confront a lot of problem.

[Bob_Schor]

As a non-engineer who is recording biosignals, I've learned that when dealing with electrical signals, you need to know lots of details to understand what is happening and make sensible suggestions, including:

• the complete circuit (all of the pieces, including amplifiers, computers, power supplies, etc.
• how grounding and signal shielding is being provided (including cabling -- are you using shielded cables?  Is the shielding connected at both ends?)
• if you are making measurements (such as the image you provided), where in the circuit are you measuring, and are you measuring with the entire circuit running or just that component in isolation?
• if you are using Computers and Software (e.g. LabVIEW) as part of your recording and control system, the computer (DAQ) hardware needs to be indicated in the circuit, along with details about cabling.
• all of the LabVIEW code needs to be described, or, even better, provided.  Since it is probably a Project with (I hope) lots of VIs, compress the enclosing disk folder and attach the resulting .ZIP file.

Noise in electrical circuits is inevitable.  What is important is to get the noise level below the level of the signal you expect to record.  It would help to know what this is, what frequencies and amplitudes you expect.  What sampling rate do you think is important, both from a Control and a Data Acquisition perspective?

Bob Schor

[Dennis_Knutson]

Bob,

You are answering a year old question.