Outline

1
Outline

• Background / Motivation
• Problem Statement
• Client Requirements
• Design Alternatives
• Final Design
• Limb Structure
• Heating Element
• Temperature Measurement
• Data Acquisition and Analysis
• Testing
• Future Work

2
Background

• Cast Burn
• Normal skin temperature is 30-35 C
• Exothermic reactions can cause the skin surface
  to reach up to 60 C
• Burns can be caused by temperatures as low as 45
  C

3
Background

• Time and temperature affects burn severity

4
Background

• Previous study examined factors that affect the
  internal temperature of cast curing
• Cast thickness
• Dipping water temperature
• Limb construction
• Pyrex cylinder
• Heated by water bath
• No real-time display

5
Motivation

• The goal of this project is to prevent cast burns
  by understanding the correlation between external
  and internal cast temperature
• Temperature monitors, such as liquid crystal
  thermometers, will be placed on the cast surface
  during curing process
• Using the internal and external temperature
  correlation, doctors will know when to remove the
  cast to prevent burns

6
Problem Statement

• Develop system to study the correlation between
  internal and external cast temperatures to
  ultimately prevent cast burns.
• Limb structure that maintains skin temperature
• Temperature sensors to measure internal and
  external temperatures
• Data acquisition system that displays and records
  real-time temperature data

7
Client Requirements

• Stable limb structure that maintains surface
  temperature of 30-35 C
• Temperature measurement accuracy of 1C
• Repeatability of approximately 50 trials
• Budget within 1500
• Computer analysis software

8
System Schematic
Heater
Thermocouples
Cast
Limb Structure
Data Logger
9
Design Alternatives

• Flexible Silicone Heater
• Nichrome wire embedded in flexible silicone
• Power controller ensures constant temperature
• Adhesive backing to mount to any material
• Not designed for use in low temperature
  applications

10
Design Alternatives

• Circulating Water Bath
• Pumps heated water through closed cylinder
• Maintains constant temperature within .05 C
• Possible safety issues with water in close
  proximity to electrical equipment
• Expensive and not portable

11
Design Alternatives

• Air-therm Heater
• Circulates heated air through closed cylinder
• Precise temperature control and uniformity
• Portable and clean
• Exceeds budget

12
Final Design

• The final design includes
• PVC limb structure
• Carbon fiber flexible heater
• Thermocouples 2 internal, 2 external
• Data logger
• Acquisition and analysis software

13
Limb Structure

• Polyvinylchloride 3 diameter pipe
• Durable, lightweight, and stable
• Covered with the flexible heating element
• 15 length of casting surface
• Supported by wooden frame
• Easy to use and compact

14
Heating Element

• Thermion carbon fiber heater
• Inexpensive
• Even heat distribution
• Designed for low temperature operation
• Two 7 x 15 in parallel

Carbon Fiber
Wire
15
Temperature Measurement

• Thin wire thermocouple
• Accuracy within one degree
• .025 diameter will not interfere with casting
  procedure
• Type T - male subminiature
• Sensor placement
• 2 internal and 2 external

16
Data Acquisition and Analysis

• Microdaq Data Logger
• Records up to 26,214 measurements per channel
• Four thermocouple inputs
• Internal memory chip
• MadgeTech Software
• Displays and records real-time temperature data
• Simple user interface
• Windows via USB

17
Decision Matrix
18
Testing

• Calibration testing to determine appropriate
  power setting for desired heater temperature

19
Future Work

• Consult with the client to re-evaluate goals
• Develop a standardized testing procedure
• Test the system with casting materials
• Research liquid crystal thermometers
• Determine an appropriate power supply for the
  heater (for client use)

20
Materials and Cost

• Thermion carbon fiber heater - 50
• Physitemp thermocouples - 80 each
• Microdaq data logger and software - 600
• Limb Structure - 20
• Additional items - 50
• Building a burning limb priceless