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MECH XXXXXXXXXXManufacturing Engineering Assignment 1 Part B (12.5%) Due Friday 11:59pm 24th of March (Week 5) Data Acquisition and LabVIEW – Pulse Oximetry Case Study Background: A...

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MECH XXXXXXXXXXManufacturing Engineering
Assignment 1 Part B (12.5%)
Due Friday 11:59pm 24th of March (Week 5)
Data Acquisition and LabVIEW – Pulse Oximetry Case Study


Background:
A pulse oximeter is a non-invasive medical device used to measure the percentage oxygen saturation in the
lood. Oxygen saturation should always be above 95%, although in those with long-standing respiratory disease
or cyanotic congenital heart disease, it may be lower, co
esponding to disease severity. The pulse Oximeter
operates by shining light at two different wavelengths through part of the patient’s body where blood is present
such as a finger or earlobe, and monitoring the change in light absorption due to the blood pulsing.
In general, haemoglobin can be saturated with oxygen molecules (oxyhaemoglobin), or lacking oxygen
molecules (deoxyhaemoglobin). The absorption spectra of oxyhaemoglobin and deoxyhaemoglobin differ. The
oxyhaemoglobin has significantly lower absorption of red light than deoxyhaemoglobin, while for infrared light
its absorption is slightly higher. This difference accounts for the presentation of cyanosis, the blue to purplish
colour that tissues develop during hypoxia (when the body is deprived of oxygen).This difference is also used for
measurement of the amount of oxygen in patient's blood by the pulse oximeter.
The raw signal received from the pulse oximeter transducer at each wavelength has the AC pulse component
we are interested in on top of a large offset, as the abso
ance change caused by the blood pulse is small
compared to the absorption of the rest of the tissue the light must pass through.
It is the ratio of the AC pulse peak values measured between the two wavelengths that is used to calculate the
percentage of oxygen saturation in the blood.
http:
en.wikipedia.org/wiki/Absorption_spectrum
http:
en.wikipedia.org/wiki/Cyanosis
http:
en.wikipedia.org/wiki/Hypoxia_(medical)
http:
en.wikipedia.org/wiki/Pulse_oximete
The pulse oximeter uses very complicated calculations to work out oxygen saturation that depend on the exact
light wavelengths used by the device. The formulas and outputs are also cali
ated using historical databases
of known blood oxygenation levels compared with actual peak ratios measured from the device.
To keep things simple for the purposes of this assignment, let us assume that the ratio of the red and infrared
absorption peaks can be converted to percentage oxygen saturation using the simple linear relationship below,
which approximates the actual conversion formulas:
Oxygen Saturation (%) = -34 X R + 117
Where R = Red Peak / IR Peak
Part a: System Design (3.5 Marks)
Many things must be considered when choosing appropriate data acquisition hardware for use in a product,
including but not limited to sample rate, resolution, channel numbers, and cost.
1. With this in mind, give the minimum frequency (in Hz) needed to measure the pulse oximeter
signal. Assume human heart rates can range from 32 beats per minute to 220 beats per minute.
To measure peak values, you will need to sample fast enough to obtain a good pulse shape, and in
the case of this application we would like to see at least 100 points representing each signal period
(entire pulse).

2. Assuming you want a minimum of 3 pulses for calculations how long will you need to capture the
signal for on the DAQ device?

3. Calculate the minimum resolution (in bits) needed to measure the pulse oximeter signal. Assume
that you need to resolve a change of 0.001V in the signal and the DAQ device has a range of ±10V.

4. Which of the following National Instruments DAQ cards would be the best choice for this
application (note: you will have to look up the specifications for these DAQ cards on ni.com). Please
provide reasoning.
a. NI USB-6000
. NI USB-6002
c. NI USB-6525
d. NI USB-6351

5. The pulse oximeter sensor outputs a 0-15V signal typically with high frequency noise up to 150Hz.
Discuss the signal conditioning we should consider?

6. Provide a diagram of the Data Acquisition system, from the PC to the sensor, including required
software components.
Part b: Analysing the Acquired Data using LabVIEW (9 Marks)
Using the signals in the file “Pulse Oximetry Raw Data.lvm”, use LabVIEW to determine:
a. The oxygen saturation of the patient (%)
. Check that the oxygen saturation is within a healthy range of 95% to 100% (inclusive)
c. The heart rate of the patient (Beats Per Minute)
d. Check that the heart rate is within a healthy range of 50 BPM to 90 BPM (inclusive)
e. Write the results to a .csv file, including header information, that opens in both Notepad or other text
editor and Excel as shown below:
Figure 1: CSV File output example shown in Notepad and Excel
Development Guide:
a. Start by loading the “Pulse Oximetry Raw Data.lvm” data into a new LabVIEW VI by using a “Read From
Measurement File” Express VI.
. Plot the raw Red and Infra-Red (IR) waveforms on a graph. You will notice that the interesting part of
the waveforms is offset, as the abso
ance change caused by the blood pulse is small compared to the
absorption of the rest of the tissue the light must pass through.
c. Find the DC offset and remove it from the raw data.
d. Remove measurement noise and plot the processed waveforms on a graph.
e. Use Express VIs and basic a
ay and numeric functions to determine and display the oxygen saturation
and heart rate of the patient.
f. Use LabVIEW functions to check that the oxygen saturation and heart rate of the patient are within
their healthy ranges and display a clearly visible warning if they are not.
g. Write your results to a .csv file that can open in Excel.
Submission instructions
You will need to submit two documents, your LabVIEW VI for Part b and a Word or .PDF document explaining
your answers to Part a.
When you have completed your written answers and LabVIEW program, include your SID in each filename as
per the example below, compress in a zip file as described below, and upload your files through Canvas.
XXXXXXXXXXdocx
XXXXXXXXXXvi
Compress to single file for upload: XXXXXXXXXXzip
If these rules are not adhered to, your assignment will not be marked!
Part a: (3.5 Marks)
Submit your answers, calculations, and reasoning as a Word or .PDF Document.
Part b: (9 Marks)
Submit your LabVIEW file(s). The following calculated values should be clearly displayed on the user interface
upon running the program.
• Oxygen Saturation (%)
• Heart Rate (BPM)
As well as receiving marks for the co
ect file reading setup and calculation results, your LabVIEW code will be
used to analyse your methodology and understanding of the software package. Your code will be used to provide
partial marks where relevant. Consider the following:
• Logical function/vi selection and ordering
• Meaningful labels on graphs and indicators
• Intuitive Front Panel design
• Ease of use (consider file paths)
• Block Diagram Comments
• Neat, readable code that is not overly complicated
Answered 6 days After Mar 17, 2023

Solution

Dr Shweta answered on Mar 23 2023
22 Votes
Part A solution
Ans 1. The minimum frequency (in Hz) needed to measure the pulse oximeter signal for human heart rates in a given range of 32 beats per minute to 220 beats per minute.is 0.53 Hz to 3.42 Hz.
Ans 2. For a minimum of 3 pulses the signal on the DAQ device have to be captured for 0.0028 mS
Ans 3. The minimum resolution of 16 bits is required for measuring the pulse...
SOLUTION.PDF

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