Lecture 22 Force Displacement

1
Lecture 22Force - Displacement
2
Outline of Class today

• Error in Blood pressure measurements
• Systems design
• Review 2nd order systems
• Other pressure sensors bourdon tubes
• Millar catheter transducer
• Measuring pressure indirectly in capillaries
• Statham transducer air bubble danger
• Bridge circuit modulation/demodulation
• Optical transducers
• Eye pressure measurements

3
Other 2nd order systems
Mechanical systems Body motion Fluid
systems Transducer sensors Oxygen diffusion
models Feedback model elements
4
Simple pressure transducers - Bourdon tube-
Bellows
5
Millar pressure sensor
6
Indirect capillary pressure measurements
7
Optical pressure catheter sensor
8
Statham Transducer
Dangers of Air Bubble -loss of frequency
fidelity -air bubble entering blood -Possible
stokes or ministrokes
9
Pressure sensor for Eye Pressures
10
Displacement Transducers

• Potentiometers
• Strain Gages
• Inductive type
• LVDT
• Capacitive type

11
Resistive displacement transducers
12
Linearization methods
13
Wire Non-linearities
14
Strain Gages(wire type)
15
Strain gage(semiconductor)
16
Strain Gage(mercury belt)
17
Strain Gage Equation
18
Strain Gage Equations
19
Gage Factors
20
Inductive transducers
21
Linear Variable Displacement Transducers (LVDT)
22
Capacitive transducers
23
LVDT on Bourdon tube