CH10: Force Measurement Flashcards
What is Electromechanical Transduction?
Electromechanical transduction occurs when a mechanical action results in a change in electric potential.
What is electrical potential commonly known as?
Voltage (or electromotive force)
What is the electrical potential?
It is the force that causes electrons to flow from one part of a circuit to another part of a circuit.
The flow of electrons is also known as…
Electrical current
What do electromechanical transducers create?
Create a change in electric potential – they either increase or decrease the electrical current flowing through a circuit
What is a common electromechanical transducer?
Potentiometer
What is a potentiometer used in?
Potentiometer’s are used in volume dials, dimmer switches, etc.
What are other commonly used electromechanical transducers?
- Potentiometer
- Accelerometers
- Gyroscopes
- Force sensor
What is an accelerometer used for?
Measures acceleration
What is a gyroscope used for?
Measure angular velocity in 3 axes
What are the two commonly used force sensors in biomechanics?
- Piezoelectric sensor
- Strain gauge
What is a piezoelectric sensor?
- Uses quartz crystal
- Compressing crystal generates change in electric potential difference
Example: Force platforms: Kistler
What is a strain gauge?
- Uses thin metal foil
- Stretching or compressing metal foil generates change in electric potential difference
Example: Force platforms: AMTI, Bertec
Electrical circuits will always have a minimum of __________ electrical contacts.
two
What are load cells?
Strain gauges are instrumented in a load cell for force measurement. There are many designs for load cells, but they generally consist of a steel or aluminum body that the
strain gauge is laminated to.
What are the two examples of load cells?
- “S-Type” load cell: tensile or compression
- “Inline” load cell: tension
What can electromechanical transducers be used for?
- Calibration: Determine relation between voltage and magnitude of physical phenomenon
- Measure voltage
- Calculate magnitude of physical phenomenon
What is the calibration coefficient?
An increase of 1.0 V is equal to an increase in 447.43 N – or put another way there are 447.43 N/V.
What is one major feature that is important in analog-to-digital conversion?
Conversion rate or sampling frequency
What is a multi-axis force platform?
A multi-axis force platform has 6 load cells, configured in a manner to measure forces in 3 axes and moments of force about 3 axes. The multi-axis or “true” force platform provides a lot of information, which is not possible form a “single-axis” or “vertical-only” force platform.
What is the centre of pressure (COP)?
The point of force application. The coordinate system not only defines the direction of the forces, it is part of determining the point of force application.
What is the pressure formula?
Pressure = Force / Area
What are the types of standing balance?
- Double-limb standing
- Single-limb standing
Motion of body’s mass is reflected in changes what?
centre of pressure location
What is postural sway?
Measuring COP provides an indicator of the amount and magnitude of this motion,
