Instrumentation notes

8/17/2019 Instrumentation notes

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2. Instrumentation and Control

Instrumentation - Sensors and actors

2.1 Instrumentation - Capteurs et actionneurs

Instrumentierung - Sensoren und Aktoren

courtesy ABB

Prof. Dr. H. Kirrmann

ABB Research Center, Baden, Switzerland2012 March, HK

Industrial Automation Automation Industrielle

Industrielle Automation



Instrumentation 2.1 - 2Industrial Automation

2.1.1 Market

2.1 Instrumentation2.1.1 Market2.1.2 Binary instruments

2.1.3 Analog Instruments2.1.4 Actors2.1.5 Transducers2.1.6 Instrumentation diagrams2.1.7 Protection classes

2.2 ontrol2.3 Programma!le "ogic ontrollers




The instrumentation market

#merson $%is&er'(osemount)* 27 +In,ensys* 4'5+

ABB* 4'5+-oneyell* 3'4+

one dominant /layer a lot o0 small /layers




Example Nuclear power plant

Nombre de capteurs et d’actionneurs pour une tranche et selon les paliers

(number of sensors and actors for each slice and according to the level)

Capteur ou actionneur

(sensor or actor) | (Sensor oder Aktor)

Tranches

900 MW

Tranches

1300 MW

Tranches

1450 MW

Capteurs tout ou rien

(binary sensors) | (Initiatoren)1 930 1 560 1 660

Fins de course de vannes manuelles et de registres

(position sensor for manual valves and dampers330 140 700

Capteurs analogiques (mesures)

(analog sensors) | (Analoge Messgaräte)1 360 2 050 2 280

Appareils de coupure 6,6 / 7,2 kV(circuit breakers) | (Leistungsschalter)

40 95 74

Contacteurs 380 V

(switches 380V) | (Schalter) 340 600 540

Vannes motorisées

(motor valves) | (Steuerschieber) 190 300 250

Robinets pneumatiques TOR

(on-off pneumatic switches) | (pneumatische Schalter) 480 470 670

Vannes réglantes

(proportional valves) | ( Regelschieber) 180 500 110

ean -AB#(T Bernard APP#"" uy #I#( 1889


http://slidepdf.com/reader/full/instrumentation-notes 5/61Instrumentation 2.1 - 5Industrial Automation

Concepts

instruments : sensors $capteurs, Messgeber ) and actors $actionneurs, Stellglieder )

!inary $on;o00) and analog $continuous) instruments are distinguis&ed.

industrial conditions*

< tem/erature range commercial* $=> to ?7=>)industry $'4=>..?95>)

e@tended industrial$4=>..?125>)

< mec&anical resilience $s&ocks and ,i!rations) # 6==69< /rotection* #lectro'Magnetic $#M)'distur!ances # 55=22 #55=24)< /rotection* ater and moisture $IP67:com/letely sealed IP2= : normal)< /rotection* #MP $uclear #M Pulse) ' ater distri!ution ci,il /rotection< mounting and re/lacement< ro!ust connectors< /oer* mostly 24C: !ecause o0 !attery !ack'u/ sometimes 49C:)



2.1.2 Binary Instruments


2.1.3 Analog Instruments2.1.4 Actors2.1.5 Transducers2.1.6 Instrumentation diagrams2.1.7 Protection classes




Binary position measurement

!inary sensors $Geber DInitiator D indicateur "tout ou rien" )*

<micro'sitc& $Endschalter contact fin de course) ?c&ea/ 'ear !ouncing

<o/tical sensor $Lichtschranke barrière optique) ?relia!le 'dust or liEuid sensiti,e

<magnetic sensor $Näherungsschalter détecteur de proximité ) ?dust'insensiti,e ' magnetic



Binary Signal processing

P&ysical attac&ment"e,el ada/tation

al,anical se/aration#M !arrier $against s/arks radio distur!ances)

AcEuisitionon,ert to standard le,els(elay contacts 24C $most 0reEuent) 49C 11=C $electrical su!stations)#lectronic signals 24C FG1=C'6=C

Hut/ut* =..24C1==mAounter in/uts* ray B or !inary

Processing%iltering $e.g. =..9 ms 0ilter)Plausi!ility $ Antivalen Antivalence)

Bounce'0ree $Entprellen! Anti-rebond )



2.1.3 Analog Instruments


2.1.3 Analog Instruments2.1.3.1 Position and s/eed2.1.3.2 Tem/erature2.1.3.3 -ydraulic

2.1.4 Actors2.1.5 Transducers2.1.6 Instrumentation diagrams

2.1.7 Protection classes2.2 ontrol2.3 Programma!le "ogic ontrollers



Precision (repeatability) and accuracy (deviation)

ot /reciseot accurate

ot /recise Accurate

Preciseot accurate

Precise Accurate

Accuracy is a conseEuence o0 systematic errors $or !ad cali!ration)accuracy and /recision may de/ends on time $dri0t)



Resolution and accuracy

• Resolution expresses how many different levels can be distinguished

• It is not related to accuracy



2.1.3.1 Analog mechanical position

potentiometercapacitive

balanced transformer (LVDT)(linear or sin/cos encoder)

strain gaugespiezo-electric

+cheap, -wear, bad resolution+cheap, -bad resolution

+reliable, robust - small displacements

+reliable, very small displacements+extremely small displacements



Variable differential transformer (LVTD)

T&e "CT is a ,aria!le'reluctance de,ice &ere a /rimary center coil esta!lis&es amagnetic 0lu@ t&at is cou/led t&roug& a mo!ile armature to a symmetrically'oundsecondary coil on eit&er side o0 t&e /rimary.

To com/onents com/rise t&e "CT* t&e mo!ile armature and t&e outer trans0ormerindings. T&e secondary coils are series'o//osedJ ound in series !ut in o//ositedirections.

source* .sensorland.com

K&en t&e mo,ing armature is centered !eteen t&e to series'o//osed secondaries eEual magnetic0lu@ cou/les into !ot& secondariesJ t&e ,oltage induced in one &al0 o0 t&e secondary inding is 19=degrees out'o0'/&ase it& t&e ,oltage induced in t&e ot&er &al0 o0 t&e secondary inding.K&en t&e armature is mo,ed out o0 t&at /osition a ,oltage /ro/ortional to t&e dis/lacement a//ears



Capacitive angle or position measurement

: L A

d≈α

α

0i@ed

mo,a!le

ca/acitance is e,aluated !ymodi0ying t&e 0reEuency o0an oscillator




Small position measurement strain gauges

( = ρ

A

2

C

A

= ρ

,olume : constant ρ : constant

D

tem/erature com/ensation

!y dummyN gauges

0reEuently used in !uildings !ridgesdams 0or detecting mo,ements.

Princi/le* t&e resistance o0 a ire it& resisti,ity O increases &en t&is ire is stretc&ed*

Dehnungsmessstreifen $M) "auges de contrainte

≈2

o

(1

measure

(2

com/ensation(4

(3

measurement in !ridge$i0 = : =* (1(4 : (2(3)

O : resisti,ity




!ie"o-electrical e##ect

source* Qistler

PieRoelectric materials $crystals) c&ange 0orm &en an electrical 0ield is a//lied to t&em.on,ersely /ieRoelectric materials /roduce an electrical 0ield &en de0ormed.

SuartR transducers e@&i!it remarka!le /ro/erties t&at usti0y t&eir largescale use in researc& de,elo/ment /roduction and testing.T&ey are e@tremely sta!le rugged and com/act.

H0 t&e large num!er o0 /ieRoelectric materials a,aila!le today EuartR is

em/loyed /re0erentially in transducer designs !ecause o0 t&e 0olloinge@cellent /ro/erties*

< &ig& material stress limit around 1== MPa $U 14 km ater de/t&)

< tem/erature resistance $u/ to 5==)

< ,ery &ig& rigidity &ig& linearity and negligi!le &ysteresis

< almost constant sensiti,ity o,er a ide tem/erature range< ultra &ig& insulation resistance $1=?14 o&ms) alloing lo0reEuency measurements $V1 -R)




!rinciple o# optical angle encoder

courtesy Parker Motion & Control

H/tical encoders o/erate !y means o0 a grating t&at mo,es !eteen a lig&t source and a detector.T&e detector registers &en lig&t /asses t&roug& t&e trans/arent areas o0 t&e grating.

%or increased resolution t&e lig&t source is collimated and a mask is /laced !eteen t&e gratingand t&e detector. T&e grating and t&e mask /roduce a s&uttering e00ect so t&at only &en t&eirtrans/arent sections are in alignment is lig&t alloed to /ass to t&e detector.

An incremental encoder generates a /ulse 0or a gi,en increment o0 s&a0t rotation $rotary encoder)or a /ulse 0or a gi,en linear distance tra,elled $linear encoder). Total distance tra,elled or s&a0tangular rotation is determined !y counting t&e encoder out/ut /ulses.

An a!solute encoder &as a num!er o0 out/ut c&annels suc& t&at e,ery s&a0t /osition may !edescri!ed !y its on uniEue code. T&e &ig&er t&e resolution t&e more out/ut c&annels arereEuired.




Incremental angle encoder

P&oto* Baumer

o/en mounted

P&oto* "enord W Bauer




courtesy ParkerMotion & Control

A$solute digital position %ray encoder

1 2 3 4 5 6 7 9 8 1= 11 12 13 14= 15

1 2 3 4 5 6 7 9 8 1= 11 12 13 14= 15

"B

MB

"B

MB

!inary code* i0 all !its ere to c&ange at a!out t&e same time* glitc&es

ray code* only one !it c&anges at a time* no glitc&

ray disk $9 !it)

=======1

==1===11=1===1=1=11==111

=======1==11==1=

=11==111=1=1=1==




Linear encoder

Also it& magnetic instead o0 o/tical grating




&orce measurement

%orce ; TorEue ; Keig&t ; Pressure is measured !y small dis/lacements $% : k < @)*

' /ieRo'electrical transducers' strain gauges

Acceleration is measured !y ay o0 0orce ; dis/lacement measurement $% : M < γ )

Analogspeedmeasurement:tachometer




Analog speed measurement: tachometer

angular s/eed ω

i U dω ; dt0 U ω

transducer analog* 4..2= mA

digital* =1=11=11=

7

6

a sim/le tac&ometer is a rotating /ermanent magnet t&at induces a ,oltage into a statorinding.

t&is ,oltage is con,erted into an analog ,oltage or current later con,erted to a digital

,alue

alternati,ely t&e 0reEuency o0 t&e signal can !e measured to yield directly a digital ,alue




Measuring distance without mechanical contact

principle inducti'e optical ultra-sound

range =..1=mm 15..1=== mm 2=..2588mmresolution =1Xm 2Xm 3==Xmre/eata!ility 1Xm 2Xm 5==Xmlinearity =4..5+ ==6..12+ =5+reacti,ity =35ms =8ms 3=msremark 0or electrically 0or small and &ig&ly linear

conducting mo!ile /arts long rangematerials small dust resilient

c&ea/

laser

#@am/le* o/tical range0inder




2.1.3.2 Temperature measurement

t&e most 0reEuently measured ,alue in industry

.omega.com

T&ermoell

#@tension Assem!lies

Protection and&ead assem!ly

T t t




Temperature measurement

Spectrometer *measures in0rared radiation !y /&oto'sensiti,e semiconductors? &ig&est tem/erature measures sur0aces no contact

' &ig&est /rice

Thermistance $(T ' resistance tem/erature detector )*metal &ose resistance de/ends on tem/erature*

? c&ea/ ro!ust &ig& tem/erature range $ '19=Y ..6==Y)' reEuire current source non'linear.

Thermistor $T ' negati,e tem/erature coe00icient)*semiconductor &ose resistance de/ends on tem/erature*? ,ery c&ea/ sensi!le' lo tem/erature im/recise needs current source strongly non'linear 0ragile sel0'&eating

Thermo-element $#hermoelement! thermocouple)*/air o0 dissimilar metals t&at generate a ,oltage /ro/ortional to t&e

tem/erature di00erence !eteen arm and cold unction $ee!eck e00ect)? &ig& /recision &ig& tem/erature /unctual measurement' lo ,oltage reEuires cold unction com/ensation &ig& am/li0ication lineariRation

Bimetal $$imetall ! bilame)*mec&anical $yes;no) tem/erature indicator using t&e di00erence in t&e dilatationcoe00icients o0 to metals ,ery c&ea/ idely used $toasters...)

Th l t d Th i t




Thermo-element and Thermo-resistance

Thermo-element(Thermocouple)

Thermoresistance(semiconductor or metal)

Platinum (Pt 100)

Fe-Const

also: Pt/Rh - Pt

θ2θ1Fe

Constantan

Cu

Cu

U ≈ (θ2-θ1)

U ≈θi = constant

θ3θ4

2 or 4 wire connection (to compensate voltage drop)

2,3- or 4-wire connection

reference temperature(cold junction)

4..20 mA

4..20 mA

θ

measured temperature(hot junction)

two dissimilar

electricalconductors

one material whoseresistance istemperature-dependent

extensionwire

Coldjunctionbox




Cold junction box

2 1 3 3 (ydraulic measurements




2.1.3.3 (ydraulic measurements

•Flow,•Mass Flow,•Level,

•Pressure,•Conductivity,•pH-Sensor,•Viscosity,•Humidity,

special requirements: intrinsic safety = explosive environment, sea floor = high pressure

)e'el measurement




)e'el measurement

</ulsed laser

<load cell

</ulsed microa,e

<nuclear

<ultrasonic $4='6= k-R)

<lo /oer ultrasonic

detector ro

see ontrol #ngineering Aug 2==3

% : mg

Flowmeasurement




Flow measurement

istinguis&*,olumetric 0lo $ m3;s)

mass 0lo* $kg ; s)identical &en t&e density o0 t&e liEuid is constant

main met&ods*'0loater 'tur!ine'/ressure di00erence

',orte@'tem/erature gradient'ultrasonic'electrodynamics

&lo* 'elocity measurement di##erential pressure +2 methods,




&lo* 'elocity measurement di##erential pressure +2 methods,

occultation(Verengung)

membrane

the flow velocity is proportional to the square root of the pressure difference

piezo-electricsensor

/2 ' /1 : ρ ,2

1

2 (Bernoulli effect)

/2 /1

,

fluid ofviscosityρ

21

occultation(Blende)

&lo* measurement




&lo* measurement

Ht&er means*

Magnetic'dynamic

oriolisltra'sound

Flowmeasurementinaplant




Flow measurement in a plant

2.1.4 Actors




2.1 Instrumentation2.1.1 Market2.1.2 Binary instruments2.1.3 Analog Instruments2.1.4 Actors2.1.5 Transducers2.1.6 Instrumentation diagrams2.1.7 Protection classes


Actors +Actuators,




+ ,

A!out 1=+ o0 t&e 0ield elements are actors $t&at in0luence t&e /rocess). Actors can !e !inary $on;o00) or analog $e.g. ,aria!le s/eed dri,e)

T&e most common are*' electric contactors $relays)' &eating elements' /neumatic and &ydraulic mo,ers $,al,e /um/)' electric motors $rotating and linear)

Actors are controlled !y t&e same electrical signal le,els as sensors use$4..2=mA =..1=C =..24C etc.) !ut at &ig&er /oer le,els e.g. to directly mo,e a contactor$dis"oncteur ).

tellantrie!e Servomoteurs

Electric Motors




olenoids motor

Async&ronous Motors $Induction)ync&ronous motorste/ motors reluctance motors

Drives (variateurs de vitesse, Stellantriebe)




Caria!le s/eed dri,es control s/eed and acceleration and /rotect t&e motor $o,er'current torEue tem/erature).

-ig&'/oer dri,es can 0eed !ack energy to t&e grid &en !raking $in,erters).ri,es is an on market $Automation W ri,esN)

sim/le motor control ca!inet 0or /oer o0 G 1= kK small dri,e control V 1= kK

$(ockell)

Motors and dri,es are se/arate !usinesses

)inear Motors




source* "inMot $;.linmot.com)

(ydraulics and #luidics




Pumps, valves, rods,…

source* .!ac&o0en.c&

fluidic switches

switchboard ("Ventilinsel")

the most widespread actor in industry(lightweight, reliable, cheap)

I/P or E/P = electro-pneumatic transducers

2.1. Transducers




2.1 Instrumentation2.1.1 Market2.1.2 Binary instruments2.1.3 Analog Instruments2.1.4 Actors2.1.5 Transducers2.1.6 Instrumentation diagrams2.1.7 Protection classes


Transducer




A transducer converts the information supplied by a sensor (piezo, resistance,…)into a standardized signal which can be processed digitally.

Some transducers have directly a digital (field bus) output and are integratedin the sensor.

Other are located at distances of several meters from the sensor.

/0ample o# analog transducer




Emergency panel

PLCControl Room

CurrentTransformer

0..1A rms

Field house

Transducer

4..20 mAΣ R = Load

High voltage

Protection

-2 mA loop standard




The transducer acts as a current source which delivers a current between 4 and 20 mA,proportional to the measurand (Messgrösse, valeur mesurée).

Information is conveyed by a current, the voltage drop along the cable induces no error.

0 mA signals an error (wire disconnection)

The number of loads connected in series is limited by the operating voltage (10..24 V).

e.g. if (R1 + R2+ R3) = 1.5 kΩ, i : 24 ; 1.5 : 16 mA &ic& is V 2= mA* HT o.k.)Simple devices are powered directly by the residual current (4mA) allowing to transmitsignal and power through a single pair of wires.

Transducer instrument

1

instrument

2

instrument

3

0, 4..20 mA

R1 R2 R3

Object

i = f(v)

10..24V

voltagesource

measurand

Analog measurements processing in the transducer




AcEuisition $Er%assung ;aisie)

orrection o0 /ressure and tem/erature measurement 0or moist gasescorrection o0 le,el in 0unction o0 /ressure/oer and energy com/utation cumulati,e measurements

(ange "imit su/er,ision Kire integrity#rror re/ort diagnostic disa!ling.

om!ined measurement

Plausi!ility

%iltering against 5=-R;6=-R noise and its &armonicscaling"ineariRation o0 sensors $Pt1== %e'onst) correction $sEuare root 0or 0lo).

A,eraging and om/utation o0 (oot Mean Euare $#00ekti,ert ,aleur e00icace)

Analog'igital on,ersion

&a/ing $ Au%bereitung ;conditionnement)

ormaliRed ignals* ='1=C 2'1=C $=;4'2=mA) Z2=mA(esistance t&ermometer $Pt1==)

T&ermo'element

2.1.6 Instrumentation diagrams: P&ID




2.1 Instrumentation2.1.1 Market2.1.2 Binary instruments2.1.3 Analog Instruments

2.1.4 Actors2.1.5 Transducers2.1.6 Instrumentation diagrams2.1.7 Protection classes


Instrumentation iagrams




Similarly to electrical schemas, the control industry (especially the chemical andprocess industry) describes its plants and their instrumentation by a

P&ID (pronounce P.N.I.D.) (Piping aNd Instrumentation Diagram),sometimes called P&WD (Piping and wiring diagrams)

The P&ID shows the flows in a plant (in the chemical or process industry) and thecorresponding sensors or actors.

At the same time, the P&ID gives a name ("tag") to each sensor and actor, along withadditional parameters.

This tag identifies a "point" not only on the screens and controllers, but also on theobjects in the field.



!4I




The P&ID mixes pneumatic / hydraulic elements, electrical elementsand instruments on the same diagram

It uses a set of symbols defined in the ISA S5.1 standard.

Examples of pneumatic / hydraulic symbols:

pipe

valve

binary (or solenoid) valve (on/off)

3 k5 heater

vessel / reactor

pump, also

heat exchangeranalog valve (continuous)

one-way valve (“diode”)

Instrumentation identi#ication




C1529

%I

tag name of thecorrespondingvariablehere: V1528

function(here: valve)

mover(here: solenoid)

T&e 0irst letter de0ines t&e measured or initiating ,aria!les suc& as Analysis $A) %lo $%)Tem/erature $T) etc. it& succeeding letters de0ining readout /assi,e or out/ut 0unctions suc&as Indicator $I) (ecord $() Transmit $T) see ne@t slides &ere* 0lo indicator digital

ISA S.1 %eneral instrument or #unction sym$ols




!rimary location

accessi$le to

operator

&ield mounted

Au0iliary location

accessi$le to

operator

iscreteinstruments

Shared

display6 shared

control

Computer#unction

!rogramma$le

logic control

1. Symbol size may vary according to the user's needs and the type of document.2. Abbreviations of the user's choice may be used when necessary to specify location.3. Inaccessible behind the panel! devices may be depicted using the same symbol but with adashed horizontal bar.Source" #ontrol $ngineering with data from ISA S%.1 standard

/0ample o# !4I




%T1=1 is a 0ield'mounted 0lotransmitter connected ,ia

electrical signals $dotted line) to0lo indicating controller %I1=1 located in a s&aredcontrol;dis/lay de,ice

Euare root e@traction o0 t&ein/ut signal is /art o0 %I 1=1]s0unctionality.

T&e out/ut o0 %I 1=1 is an electrical signal to T[ 1=1located in an inaccessi!le or !e&ind't&e'/anel'!oard location.

T&e out/ut signal 0rom T[ 1=1is a /neumatic signal $line it&dou!le 0orard slas& marks)making T[ 1=1 an I;P $currentto /neumatic transducer)

TT 1=1 and TI 1=1 aresimilar to %T 1=1 and %I 1=1 !ut are measuringindicating and controllingtem/erature

TI 1=1]s out/ut is connected

,ia an internal so0tare ordata link $line it& !u!!les) tot&e set/oint $P) o0 %I 1=1to 0orm a cascade controlstrategy

The ISA code #or instrument type

&irst letter




Measured or initiating 'aria$le Modi#ier

A AnalysisB Burner com!ustionC sers c&oice

sers c&oice i00erential/ Coltage& %lo rate (ation $0raction)% sers c&oice( -andI urrent $electrical)7 Poer can8 Time time sc&edule Time rate o0 c&ange) "e,el

M sers c&oice Momentary9 sers c&oice: sers c&oice! Pressure ,acuum; Suantity Integrate totaliRer < (adiationS /eed 0reEuency a0etyT Tem/erature= Multi,aria!le> Ci!ration mec&anical analysis5 Keig&t 0orce? nclassi0ied \ a@is @ #,ent state or /resence [ a@is Position dimension ^ a@is

Common connecting lines




onnection to /rocess orinstrument su//ly

Pneumatic signal

#lectric signal

a/illary tu!ing $0illed system)

-ydraulic signal#lectromagnetic or sonic signal$guided)Internal system link$so0tare or data link)Source" #ontrol $ngineering with data from ISA S%.1 standard

P&ID in computer readable form: IEC 62424




1

2

3

connections !eteeno!ects

au@iliary signals

location categories

role

A#\ com/onentli!rary

2.1.7 Protection Classes




2.1 Instrumentation2.1.1 Market2.1.2 Binary instruments2.1.3 Analog Instruments

2.1.4 Actors2.1.5 Transducers2.1.6 Instrumentation diagrams2.1.7 Protection classes


%erman I!-!rotection classes




2nd digit *ater

= none

1 ,ertically 0alling

2 ,ertically dro//ing 15> 0rom ,ertical

3 s/raying 6=> 0rom ,ertical

4 s/raying any direction

5 et any direction

6 strong et any direction

< /rotection against tem/orary di//ing$3= mn 1 m)

< /rotection against /ermanent di//ing

< 8Q ater in &ig&'/ressure steamas&ing

1st digit touching o$ects

= none

1 large !ody o!ect G 5= mm _

sur0ace2 0inger o!ect G12.5 mm _

3 tools ires o!ect G 2.5 mm _

4 co,ered o!ect G1 mm _

5 dust

6 &ermetical0or dust

e.g. IP 67 connector

/0plosion protection




Instruments that operate in explosive environments(e.g. petrochemical, pharmaceutical, coal mines,...) are subject to particular restrictions.

e.g.They may not contain anything that can produce sparks or high heat,such as electrolytic capacitors or batteries without current limitation.Their design or programming may not be altered after their acceptance.Their price is higher than that of standard devices because they have to undergostrict testing (Typentest, type test) by a qualified authority (TÜV in Germany)

Such devices are called Eex - or "intrinsic safety devices" (Eigensichere Geräte,"Ex-Schutz", protection anti-déflagrante, "Ex") and are identified by the following logo:

European Explosion-Proof Code




#e@'de,ices are Dsa0eD $certi0ied) to !e used in an e@/losi,e en,ironment.T&ey must &a,e /assed a ty/e test at T`% $ermany) " $A)...

iss orm* DCerordnung !er erbte und c&utRsysteme in e@/losionsge0b&rdeten Bereic&enD

&ield e'ice #aceplate +mo'ie,




Assessment




How are binary process variables measured ?

How are analogue process variables measured ?

How is temperature measured ?

What is the difference between a thermocouple and a thermoresistance ?

How is position measured (analog and digital) ?

What is a Gray encoder ?

How is speed measured ?

How is force measured ?What is a P&ID ?

What is a transducer ?

How does a 4..20 mA loop operate ?



Instrumentation notes

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