bonnie adams lab 3 postlab

bonnie adams lab 3 postlab - Bonnie Adams Parter: Arwen...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Bonnie Adams Parter: Arwen Wyatt-Mair Lab 3 postlab BME 405 Laboratory 3: Data acquisition – Aliasing – Waveform and distortion measurements – Computer-based waveform generator Introduction : The objectives of this laboratory were to measure amplitude characteristics of a sinusoidal signal and distinguish between the mean value, rms amplitude, and peak amplitude; to experiment with A/D acquisition of waveforms at rates above and below the Nyquist frequency and visualize the effect of aliasing on sampled waveforms; to discover properties of the power spectrum of a signal measured with an A/D board; to experiment with the analog output capabilities of the DAQ board; and to implement a simple computer-based waveform generator using LabVIEW. Procedure and Data : 1. AC Signal Measurements with LabVIEW In LabVIEW, we created a new DAQmx task called “AWG Voltage Task” with range +/- 10V, clock set to read 1000 samples at 500 Hz rate in continuous acquisition mode. On the block diagram (below), we added and wire together DAQmx Start Task.vi to initiate the data acquisition; Read to read the data from a single channel (multiple samples), enclosed in a while loop with 50 ms wait; Stop Task to stop acquisition; and Clear Task to deallocate the data acquisition resources. Inside the while loop we added “basic averaged DC rms.vi” connected to Read and to two meters, to display the DC value and the RMS avg amplitude. We connected the measured waveform to “waveform min max.vi” and displayed (min-max)/2 on a meter labeled Peak Amplitude. The waveform is displayed on a waveform graph.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
We connected the Arbitrary Waveform Generator with a sine wave at 100 Hz with 0 offset to ch 0 on the accessory panel to be input into the computer. On the front panel, we set the sampling rate to 1000 Hz and the number of samples to 2000. We ran the vi with different amplitudes for the sine wave and recorded the measured RMS amplitude and peak amplitude. AWG signal amplitude (V) Measured RMS amplitude Peak amplitude Theoretical RMS amplitude 0.05 0.036 0.054 0.035355339 0.1 0.072 0.1 0.070710678 0.25 0.18 0.25 0.176776695 0.5 0.36 0.5 0.353553391 1 0.71 0.99 0.707106781 2.5 1.78 2.42 1.767766953 5 3.55 4.83 3.535533906 This shows that the relationship between waveform amplitude and RMS amplitude is satisfied. Although it is not expected that the values would agree as closely at the lower amplitudes because the signal range is so large, in this case they still agree very closely. However, for comparison, we ran the vi again with the same input amplitudes, but changed the signal input range from +/-10 V to +/-100 mV. AWG signal amplitude (V) Measured RMS amplitude Peak amplitude Theoretical RMS amplitude 0.05 0.036 0.051 0.035355339 0.1 0.072 0.1 0.070710678 0.25 0.18 0.25 0.176776695 0.5 0.36 0.49 0.353553391 1 0.45 0.5 0.707106781 2.5 0.45 0.5 1.767766953 5 0.5 0.5 3.535533906 We can see in the table above that the values measured for RMS amplitude are the same in as for the previous run, up to 1 V where they are cut off at 0.5 V. This is due to
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 6

bonnie adams lab 3 postlab - Bonnie Adams Parter: Arwen...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online