Cerebrospinal Fluid Flow
Measurement Sensor
University of Arizona
TI Innovation Challenge 2014 Project Report
Team Leader:
Michael Martinez, azmikem@email.arizona.edu
Team Members: Team Jose Valdez, jmv@email.arizona.edu; Deon Eakins,
kdeakins@email.arizona.edu
Team Mervyn Abraham, mabraham@email.arizona.edu; Ernesto BarrazaValdez, ebarraza@email.arizona.edu
Team Brett Lenz, blenz@email.arizona.edu
Advising Professor:
Clayton Grantham, cbg1@email.arizona.edu
Texas Instruments
Vasco Polyzoev, vasco.polyzoev@ti.com
Mentor (if applicable):
Date:
Qty.
May 23, 2014
List all TI analog IC or
TI processor part
number and URL
1) Explain where it was used in the project?
2) What specific features or performance made this
component well-suited to the design?
1
MSP430
This was selected to receive data from the ADC and transmit the data to either a
USB or Bluetooth interface to transmit the data.
1
TPS77050
Selected this voltage regulator to decrease the supply voltage from +6V to +5V
since this was the recommended voltage for the magnetic sensor and the other
analog ICs would work with this voltage. The output voltage was sent to the
positive supply terminals of the other ICs and the inverting charge pump.
1
ADS1220
This ADC was used because it was low power, adjustable gain, and had 24 bit
resolution. Since the voltage changes were originally on the order of ones to
hundreds of µV this was needed to resolve small voltage changes.
1
TPS60400
This inverting charge pump was used to supply a negative voltage of -5V to the
instrumental amplifier (INA101HP), the LM741, and the magnetic sensor. This
was needed so there would be little to no bias in the circuit.
1
CC2541
Used for Bluetooth data transmission to a smartphone, tablet, or computer.
1
LM741
Selected this op-amp to make a 2nd order Sallen-Key low pass anti-aliasing filter
with a cutoff frequency of approximately 31 Hz. This was used to filter the signal
from the instrumental amplifier before being digitized by the ADC.
Submit your TI Innovation Challenge project to TI’s Project repository. Your team is
encouraged to post your project as early as possible- Your submission will be kept offline
until the contest has officially closed!
Instructions:
 Project Name must be labelled “TI IC Design Contest North America: Project Name
and School”
 Fill out project form (template is completely flexible) and include the following
documents
o The TI report template
o Your full class report
o Supplemental photos
o A video of your partially or fully built out design. We’d love to see your team
engaging with TI products!
Project abstract (a short high level written description of the design and motivation behind
project), 1,000 words max:
Hydrocephalus is a common medical condition, which is characterized by an excessive buidup of cerebral spinal fluid (CSF) in the brain, increasing intercranial pressure. A common
treatment for hydrocephalus involves the implantation of a ventriculoperitoneal (VP) shunt in
the ventricles of the brain leading to the peritoneal cavity (belly area). Since 80% of shunts
fail after implantation there is a need for non-invasive VP shunt diagnostics. Current VP shunt
diagnostics are limited to invasive surgical procedures and pressure measurements. Accurate
flow measurements will help neurosurgeons understand hydrocephalus, its impact on the
brain, the events leading up to shunt failure, and the causes for shunt failure. To address this
issue a flow meter has been designed and created to measure the volumetric flow rate of CSF.
The device contains a sensor and electronic circuit that converts beam deflection due to fluid
flow into a voltage change. When the magnetic beam deflects due to fluid flow the magnetic
field orientation changes and the resistance in the giant magnetoresistance (GMR) sensor will
increase or decrease causing a voltage change in the circuit. The magnitude of the voltage
change is directly related to the volumetric flow rate. The data is transmitted to a
computer/tablet/smartphone where the volumetric flow rate is displayed.
The overall system is divided into four main subsystems categorized as sensing element,
housing, electronics, and software subsystems. Each one will be referred to as subsystem A,
B, C, and D respectively. The division of the system into four main categories was determined
from the assessment of important areas of the project where major improvements are
necessary and/or critical for success of the project. The sensing element consists of an elastic
magnetic beam and permanent magnet. The device housing will encase the sensing element
and electronic subsystems. The electronics will be placed on a printed circuit board (PCB)
consisting of two GMR sensors, an analog to digital converter, a microcontroller, potentially a
Bluetooth system on chip (SoC), an antenna, and a power source. The software subsystem
includes a graphic user interface (GUI) that will display the volumetric flow rate, in ml/hr,
and notify the user when the flow rate it is either too low or too high. The shunt flow detection
system must measure volumetric flow rates in the 20-50 mL/hr range. The four subsystems
work together in order to accomplish this function. Each subsystem is organized and fits in a
specific way to complete its function. The housing acts as the central piece where everything
is placed together, it also guides interactions within the system and with the outside
environment.
Please submit your class report with this one page document. Your class report should
include the following (Max of 30 pages, excluding appendix):
 Table of contents
 List of figures and tables
 A detailed written description of the project design
 Hardware Design
 Any Software Architecture used (include any software code as part of Appendix)
 Testing and Results / Conclusions
 Future Work / Recommendations
 Acknowledgements and/or References
 Appendix: schematics, CAD drawings, Critical IC Bill of Materials (Entrants may use
Digikey Online BOM tool on www.Digikey.com), User Manual, etc.
SSQW057