Experimental Data Flashcards
Notations like mega pico etc
learn off
Types of data
Quantitative
Qualitative
Quantitative data
eg.
length = 1.24m
24 types of paints used
fram is manufactured o alpha brass
Qualitative data
eg.
it is a sad painting
masterful brush strokes
SI unit of: mass length time electrical current temperature luminous intensity amount of substance
kg m s A K cd mol
femto f
x 10 ^ -15
pico p
x 10 ^ -12
nano n
x 10 ^ -9
micro μ
x 10 ^ -6
milli m
x 10 ^ -3
centi c
x 10 ^ -2
kilo k
x 10 ^ 3
mega M
x 10 ^ 6
giga G
x 10 ^ 9
tera T
x 10 ^ 12
tabulating data
book pg 13
sensors
detect energy
transdurcers
convert energy from one form to another
is a microphone a sensor or a transducer?
-detects and converts sound energy to electrical energy - it is both
is a loudspeaker a sensor or a transducer?
-converts electrical energy to sound energy - a transducer
sensors and energy
no sensor is sensitive to only one form of energy
Measurement instrument
a measurement system
scientific instruments
- high quality measurement systems
- due to high accuracy + low uncertainty
how measurement systems work
- transducer/sensor provides input to instrument
- instrument manipulates (amplify, filter, convert to digital representation) input signal to provide useful output
The correct device has:
req accuracy
stability
robustness
appropriate cost
types of quantities
static
dynamic
static quantities
slowly varying quantities
eg. a building height
dynamic quantitites
rapidly varying quantities
eg. sound, temperature
performance characteristics of instruments
- range
- span
- linearity
- non-linearity
- hysteresis
- resolution
- repeatability
- accuracy
range
min and max values of input or output variables
span
maximum variation of input or output variables
eg. thermometer with range -40C to 100C, span is 140C
linearity
extent to which input values and output values lie on (or near) a straight line
non-linearity
a more complex relationship between input and output
hysteresis
some instruments have different loading and unloading performance
(some sensors behave differently during loading and unloading, eg. due to friction between components in instrument)
resolution
smallest change in a variable to which the instrument will respond.
repeatability
measure of the closeness of agreement between a number of readings taken consecutively of a variable, before the variable has time to change.
accuracy
difference between the indicated value and the actual value.
If instrument preforms with ideal linear behaviour then relationship between input and output can be expressed as:
y = Ax
Drift
eg. a change to ambient temp may cause a drift in output of instrument which is not due to a change in measured variable
Impact of drift
- zero drift
- sensitivity drift
calibration
process of validating a measurement technique or instrument
-compare performance of instrument w/ known standard
static calibration
- to obtain static characteristics of an instrument
- establish relationship between input (measurand) + output
- hold all inputs steady
- vary measurand + record output