I have a LabView application that I need to modify to include a lock in amplifier. The application uses a DAQ card to repeatedly capture a 0.1s sample of two signals (one signal, one reference) during a laboratory test. Previously the measurement was being made by the basic RMS module to record the VRMS of the signal, and the reference ignored. However, the measurements I am now performing are at a much lower S:N and so I'd like to use a simple LIA from the NI kit. I am happy (I think) with the setup of the LIA but I'm struggling to understand the input data requirement. It has to be a 2D array, with the reference signal identifited. However, the output from the part of the utility that captures the waveform is a 1D array of waveform. Could someone advise me on how to convert from the 1D array of waveform to a 2D array suitable for input to the LIA? As you might have guessed I'm a newbie to LabView, I'm trying to modify an application designed and assembled by a former colleague, so I'd appreciate simple suggestions! TIA.

Do you have separate 1D waveform arrays for each signal or do you have a single 1D waveform array where the signals are separate elements in the array? If it's the first, you would do something like the code below. If you have a single array, then the code would be similar - you would just use a single Index Array function. You may or may not need to transpose the 2D array. I don't know what the lock in subVI expects - channel data by row or column. Message Edited by Dennis Knutson on 03-27-2009 10:18 AM

LabVIEW

How to input 1d waveform array into lock in amplifier

Solved!

Author

Hi Dennis,

I warned you I was newbie to this!

I guess I got mixed up with when I had been looking at the output of the capture card in the automated measurement code. That outputs a 1D array of waveform (alternating between each channel). Of course, when I set up to read one channel from the TDMS file it came out as a waveform.

My apologies!