Sensors and ActuatorsChapter 4
ME 392February 13, 2012
week 5
Joseph Vignola
Sampled Time HistoriesTwo weeks back we talked about samples time histories
Frequency SpectraTwo weeks back we talked about samples time histories And last week we discussed that any time history made up discreet amounts of specific frequency components.
Frequency SpectraTwo weeks back we talked about samples time histories And last week we discussed that any time history made up discreet amounts of specific frequency components. The frequency spectrum tells us how much
of each frequency is in the time history
Electronic FilterThe filter you built is an electronic device that suppress the frequency component above a “cut-off” frequency.
Electronic FilterThe filter you built is an electronic device that suppress the frequency component above a “cut-off” frequency.
Other filters can be constructed to suppress frequency below a cut-off frequency…
Electronic FilterThe filter you built is an electronic device that suppress the frequency component above a “cut-off” frequency.
Other filters can be constructed to suppress frequency below a cut-off frequency…
Or around a frequency
Electronic FilterThe filter you built is an electronic device that suppress the frequency component above a “cut-off” frequency.
Other filters can be constructed to suppress frequency below a cut-off frequency…
Or around a frequency
Or everything but the spectral content around a specific frequency.
Electrical Transfer FunctionsBy establishing the ratio of the FFTs of the output and input of a circuit we can predict the output of a circuit given an input.
Then we can say that for any other input
Then we can say that for any other input
Mechanical Transfer FunctionsMechanical systems responded to forces or electrical inputs in a way that can be predicted by a transfer function
Sources
A loudspeaker converts an electrical signal to a quickly changing pressure field.
A shaker is a device that is a lot like speaker but outputs a force and is used for shaking things
Taken from www.school-for-champions.com
Other Sources
A laser is also a source.
An antenna is a source
Any device that has an electrical signal input and outputs a related for quantity
Taken from www.gearlive.com
Taken from atechfabrication.com
The related quantity can be a Force MotionSome form of heat
Linear SourcesA source is a linear source if there is a simple proportionality that relates the input.
Often we express the sensitivity as a transfer functionThis can either be a graph or a number that represents the behavior in a operational band For our speaker maybe something like
Taken from www.wilcoxon.com
SensorsSensors are used to measure. We will uses Force sensors AccelerometersStrain gauges Pressure sensorsBut there are all kinds of sensors
Taken from www.pcb.com
A force sensor creates a voltage proportional to an input force
SensorsSensors are used to measure. We will uses Force sensors Accelerometers Strain gauges Pressure sensorsBut there are all kinds of sensors
Taken from www.pcb.com
An accelerometer creates a voltage proportional to an input acceleration
But remember to convert this by multiplying
SensorsSensors are used to measure. We will uses Force sensors Accelerometers Strain gauges Pressure sensorsBut there are all kinds of sensors
Taken from www.sensorland.com
A strain gauge ultimately creates a voltage proportional to strain
Strain is dimensionless
Signal ConditioningThe hitch with most sensors is that they are not able to produce much (if any) electrical signal on there own.
Taken from www.pcb.com
For many sensor we need to use some other device between the sensor and the computer.
This could be aSignal conditionerA preamplifier / power supply Wheatstone bridge
Signal ConditioningThe hitch with most sensors is that they are not able to produce much (if any) electrical signal on there own.
Taken from www.b&K.com
For many sensor we need to use some other device between the sensor and the computer.
This could be aSignal conditionerA preamplifier / power supply Wheatstone bridge
Signal ConditioningThe hitch with most sensors is that they are not able to produce much (if any) electrical signal on there own.
For many sensor we need to use some other device between the sensor and the computer.
This could be aSignal conditionerA preamplifier / power supply Wheatstone bridge
ConnectorsThe connectors we use in the lab are
3.5mm or stereo mini