Eng experimentation review theory

main components for a measurement system

sensor, signal modifier ,indicator

sensing element

component of measurement system which records the physical changes of the experiment

signal modification subsystem

takes recorded data from sensor and converts it into a usable form

indicator

displays signal modification data in analog or digital

intrusive measurement system

measurements likely physically effect the phenomenon

non intrusive measurement system

measures without affecting the phenomenon being observed.

validity of measurement

refers to the accuracy and reliability of the results obtained from a measurement system. It assesses whether the measurement truly reflects the phenomenon being measured.

systematic error

a consistent, repeatable error associated with faulty equipment or experimental design that skews results in a particular direction.

random error

an unpredictable error that varies from one observation to another, often due to measurement limitations or external factors.

range of experiment

the extent or scope within which measurements are taken during an experiment, defining the limits of what is being tested and observed.

accuracy

how consistent a systems results are

precision

how close to the actual value the results are

calibration

a process of a known input value is applied to a measurement system for the purpose of observing the output value.

hysteresis

type of repeatability error which is noticed when a experiment is measured from one limit back to the original limit.

design process

need motivation to inspire the process, ask what are the needs, research the problem, sensible solution, plan by selecting promising the solution, create prototype, test prototype, improve prototype

resolution error

the difference between the smallest measurable value of a system and the true value, affecting measurement accuracy.

repeatability error

the variation in measurement results when the same experiment is repeated under identical conditions, due to inconsistencies in the measurement process.

zero offset

The amount by which a measuring instrument differs from the true value when no input signal is applied, affecting calibration accuracy.

sensitivity

The ability of a measurement system to detect small changes or variations in the input signal, directly impacting the precision of the measurements.

linearity

the degree to which a measurement system's output is directly proportional to the input signal across its range, indicating the accuracy of the system.

calibration standard

a physical artifact or reproduction of the artifact which sets the standard.

static calibration standard

a value applied to the measurement system which remains constant during data acquisition.

hysteresis of static calibration

the difference in the up and down data

accuracy of static calibration

measured output minus the line of best fit

repeatability static calibration

the largest difference of the accuracy

dynamic measurement

a value which changes with time during the experiment and does not show an instantaneous response, expressed through ode

dynamic calibration

systems which are rapidly changing, involves sinusodal or step change, response determined by analysis

zero order system n = 0

responds instantaneously to measurand

first order system n = 1

responds exponentially with time

second order system n =2

responds with decaying oscillations over time

rise time

time it takes for y/y*e to go from 0.1 to 0.9

settling time

the time it takes for the oscillations to reduce significantly

transient response

response time - rise time shifted by settling time,

frequency response

frequency of responses

benefits of electrical signal

easy to record, easy to transmit,easy to manipulate

signal conditioning

signal amplification, attenuation, filtering

signal amplification

amplifies signals by increasing voltage, may introduce a phase shift, may have lower cutoff but must have upper cutoff

signal attenuation

lowers voltage of signal to be compliant with next piece of mechanism, cannot result in extra current drawn

signal filtering

removes unwanted noise, random, uncontrollable process noise and other noise.

types of signal filters

low pass, high pass, band stop, band pass

filter classes

butterworth, chebyshev, elliptic, Bessel

problem with low pass butterworth

is its relatively slow roll-off, leading to potential phase distortion in the output signal.

finite impulse response

shifts the average

infinite impulse response

has a memory and shifts data systematically

voltmeter

records voltage across measurand

ammeter

records current across measurand

multimeter

records both current and voltage depending on setting

oscilloscope

samples input voltage, converts it to a digital format and stores it in memory

computer data acquisition systems

excepts samples from multiple sensors and can record simultaneously and will provide computer with a single data sheet

multiplexer

an electronic switch which is used as a traffic controller in a system with multiple sensors

analog to digital converter or (A/D)

is a device that converts an analog signal into a digital signal, allowing for digital processing and analysis.

quantization error

+-0.5*(vru-vrl)/2^n

discrete sampling

non continous tracks, records data at a discrete time, leads to misinterpretation of data

sample rate theorem

sampling rate must be 2x highest frequency to avoid alias frequencies

sources that contribute to variations in measurement systems

resolution, repeatability

sources which contribute to variations in measurement procedures and techniques

repeatability

sources that contribute to variations in measured variables

time variation, location variation, uncontrolled

central limit theorem

if n is sufficiently large , then x follows the normal distribution

outliers

type of data which exceeds normal acceptance, can be removed with 3 sigma and Thompson tau.

systematic uncertainty

Error due to known factors that consistently affect measurements in the same direction.

random uncertainty

Error caused by unpredictable variations in measurements, which cannot be reduced through statistical methods.