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ENGR 217 Final Pt. 1.
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ENGR 217 Final Pt. 1.
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ENGR 217 Final Pt. 1measurement in this class - ANS-look at changes in elec charac due to environmental
change. (typically measure change in voltage)
analog vs digital
and goal - ANS-analog = continuous values
digital = discrete values
goal is to change analog to digital
electrical properties example - ANS-voltage, resistance, capacitance, inductance and
others
an object or system can exhibit any of these properties
a change in any of these properties can indicate a change in the environment (ex.
capacitance of human body higher than air so that touch screen senses changes in
capacitance from the finger)
voltage - ANS-measure of electric potential (difference in potential between two points)
units: volts or Joules/coulombs
Typically you measure voltage to relate to resistance or capacitance (can use an analog
voltmeter)
Ex. typical battery has voltage diff of 1.5 V from top (+) and bottom. (Direct current)
Ex. 110 V AC in outlet with two slots
electric potential - ANS-electric potential energy of a charged particle in an electric field,
divided by amount of charge. (amount of work needed to move a unit charge from one
ref point to a specific point against the elc field)
units: volts or Joules/coulombs
DAQ (data acquisition) - ANS-ADC conversion system built in table. Under the channel
there are BNC connector (Bayonet Neill-concelman)
Analog => Digital and Digital => Analog for communication - ANS-digital transmission
like satallite to be given to the analog TV back then....but now TV screens are digital.
, speakers are analog. Cell phone is digital except for the speaker. Land lines are analog.
Analog transmission varied the electromagnetic waves to send a signal
Chips that do analog to digital - ANS-often built into modern microporocessor ...like the
Arduino later used has a ADC built in
Things to think about with an ADC - ANS-speed, input range, resolution, differential or
single ended
differential vs single ended - ANS-single ended- taken relative to DAQ elec ground (in
case air table plugg into building, so building ground) can be done with single wire
(channels 0-3 on DAQ)
differntial - voltage difference between two input wires which may not have anything to
do with DAQ ground
ex. is more accurate but harder cause need two wires and need to isolate the ADC
system from ground
(Channels 4-7 on DAQ)
Speed - ANS-measured in samples per second - units: Hertz = 1/s
Example: TV, telephones, communication we want millons of samples per second
(MHz)
and for lab we don't need that speed (kHz)
Range - ANS-ADC will have an input range (MAX voltage diff)
values can only be read in this range
values above or below range will be "clipped" and going to far outside range can
damage equipment
Ex in DAQ:
channel 0-3: have range of +/- 10 V from machine ground and more than 10V different
from ground cannot be accurately read
channel 4-7: range of 10mV differential. Voltage diff between pos and neg probes
greater than 10mv cannot be accurately read.
and the range of channels 0 through 3 is 2000 times larger than that of channel 4 and
7....idk why?
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