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Fundamentals of Industrial Control WEEK 4. This week : Temperature Measurement Terminology Temperature Sensing Technology . How was it last Week?. Recap of last Week: Remember the terms? Types of Pressure Sensors When and Where to Use What We Need to Use Did we miss any?

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fundamentals of industrial control week 4

Fundamentals of Industrial Control WEEK 4

This week : Temperature Measurement


Temperature Sensing Technology

how was it last week
How was it last Week?

Recap of last Week:

Remember the terms?

Types of Pressure Sensors

When and Where to Use What We Need to Use

Did we miss any?

Did You Read Up?

pressure measurement
Pressure Measurement
  • Pressure can be created either compression( pumping)
  • Or Expansion in a closed vessel
  • Or by Gravitational exertion in a vessel
force exerted by liquids
Force Exerted By Liquids
  • In a vessel , force exerted on the walls of the vessel have three contributing factors:
  • Height of the liquid
  • Specific gravity of the Liquid
  • Temperature of the liquid
gas laws
Gas Laws:
  • Boyles Law: P1V1=P2V2 works as long as temperature is kept constant
  • Charles Law:V1/T1=V2/T2 works as long as pressure is kept constant
  • Idela Gas law: P1V1/T1=P2V2/T2 works on the day to day applications!
pressure measurment basics
Pressure Measurment Basics
  • Manometers: U tube and Inclined designs
  • Great for low pressures
  • Still used for low pressure <10 psi applications
u tubes

27.8” of H2O=1 PSI

U -Tubes

No. 246 solid plastic inclined style stationary gage with 0-6" w.c. range.

g and a psig vs psia
G and A PSIG vs PSIA

Pounds per square inch Gauge

= reference to atmosphere on earth

Pounds per square inch Absolute

= Reference to “Space Vacuum”

PSIG= PSIA+ 14.7

types of primary sensors
Types Of Primary Sensors
  • Elastic Deformation(means they move with very little pressure)
  • Diaphragm type
  • Metallic and Non Metalic
  • Primary use is Low Pressure
  • 10 Psig and under
  • Typical is inches W.C. and 0-5 psig
bourdon types
Bourdon Types
  • P43 deflection of solid Tube

Bourdon tubes are circular-shaped tubes with an oval cross-section. The pressure of the media acts on the inside of this tube which results in the oval cross section becoming almost round. Because of the curvature of the tube ring, the bourdon tube bends when tension occurs. The end of the tube, which is not fixed, moves, thus being a measurement for the pressure. This movement is indicated by a pointer. Bourdon tubes bent at an angle of approx. 250° are used for pressures up to approx. 60 bar.

For higher pressure, bourdon tubes are used which have a number of superimposed coils of the same diameter (i.e. helical coils) or helical-shaped coils (i.e. helical springs) at one level. Bourdon tubes can only be protected against overload to a limited extent. For particularly difficult measuring operations, the Wika pressure gauge can be provided with a chemical seal as a separation or protection system.

The pressure ranges are between 0...0.6 and 0...4000 bar with a reading accuracy (or accuracy class) from 0.1 to 4.0%.

spiral type
Spiral Type
  • P44
  • Same idea as bourdon except very expensive to make and lower pressure capabiltiy
  • Also known as a helical element
when to use what
When to use what!!??
  • From 0-10 PSI use Diaphragm
  • Bellows elements are low pressure as well but are no longer used in gauges
  • From 5-30 psi Helicals are offered but are not price practical.
  • 15 psi and higher Bourdon tubes are the clear choice.

Dual Scale


Inner ScaleOuter Scale

Inner ScaleOuter ScaleFigure IntervalsMinor Grad.Figure IntervalsMinor Grad.

0/9 oz./in.2 0/15 in. H2O 1 0.2 5 0.2

0/20 oz./in.2 0/35 in. H2O 5 0.5 5 0.5

0/35 oz./in.2 0/60 in. H2O 5 0.5 10 1

0/60 oz./in.2 0/100 in. H2O 10 1 10 1


Standard Ranges


Type number1008A/AL

Size63mm (2.5"), 100mm (4")

Case304 stainless steel, dry (1008A), or liquid filled (1008AL)

Fill fluidGlycerin

Ring304 stainless steel, crimped


DialBlack figures on white background, aluminum

PointerBlack, aluminum

Bourdon tube"C" shaped bronze (vac.-600 psi and compound) Helical bronze (1000 psi-6000 psi) Helical stainless steel (10,000 psi-15,000 psi)

MovementPatented PowerFlexTM with polyester segment

SocketBrass, with O-ring case seal

RestrictorBrass throttle plug 0.013" orifice in all ranges (except vacuum and 15# psi ranges)

Connection.25 NPT lower and back

RangesVac. thru 15,000 psi and compound. Equivalent metric ranges available

AccuracyASME B40.1, Grade B, 3-2-3

Operating temperatureDry gauge: -40° F to 150° F Glycerine filled: 20° F to 150° F Silicon filled: -40° F to 150° F

Gauge Options

CaseSealed case, field-fillable (LJ) Silicone filled (GV)

Mounting hardwareU-clamp (UC), front flange (FF), retrofit flange (RF)

SocketThrottle plugs 0.007", 0.02", 0.063"


Process gauges

are .5% accuracy

Pressure psiCompound psi

0/15 30" Hg/15 psi

0/30 30" Hg/30 psi

0/60 30" Hg/60 psi

0/100 30" Hg/100 psi

0/160 30" Hg/150 psi

0/200 30" Hg/300 psi


0/400 Vacuum

0/600 30/0 in. Hg

0/800 34/0 ft H20





0/5000 NOTE: Equivalent standard kg/cm2, and kPa metric ranges are available.




diaphragm seals p46
Diaphragm Seals P46
  • Primary use: to Isolate the process from the gauge Allowing thick process and toxic chemicals;erosive;corrosive to be read accurately
  • Automatically derates to 1% BFSL
  • Types of Fills:
  • Glycerine:$ Freezes,Common and inexpensive
  • Silicone: more $$ but temperature stable
  • Fluorolube: $$$$ food Grade and Stable
  • Siphons: to isolate water/vapour from high temp steam.
  • Throttle the flow into and out of the gauge
  • Oversnubbing can block the flow and gauge will not move!!
  • Subject to plugging!
  • Use only on clean solids.!
  • Throttle screws can plug up too...
electronic measurement
Electronic Measurement
  • Strain Gauge P53
  • Capacitive element P54
  • LVDT inductance P55
  • Piezo Crystal P56
  • Capacative and Strain Gauge=90% market share!!
Capacitive: Requires more movement to sense .But is reliable technologyRosemount first ot come out with it.
differential pressure measurement
Differential pressure Measurement:
  • With orifice plates principally
  • used for flow detection and signal transmission
  • differential in Filters;room pressure
  • equivalent of two sensors interacting to one another.
thermometers p96
Thermometers P96
  • Liquid In Glass Type: Prinicpally used for Commercial Services

Expansion of An Alcohol based susbstance

to expand within a fixed volume area in a direct correlation to a fixed mechanical scale

filled systems
Filled Systems
  • Have higher volume of volatile liquid
  • Changing volume compresses gas /liquid to make a pressure exert on a Bourdon tube,identical to a pressure gauge!
  • Good accuracy at limited small ranges
  • Inaccurate at large ranges
different class grades
Different Class & Grades
  • All operate the same
  • Class 2A,B,C,D different ranges and voltile liquid fills are used…but in the end
  • They all do the same function..expand and generate pressure!
mechanical gas operated thermometer
Mechanical Gas Operated Thermometer
  • 2 1/2”(63mm), 3 1/2”(90mm), 4”(100mm), 4 1/2”(115mm), 6”(150mm), 8”(200mm) dials
  • 1/2”(12.7mm) x 6”(150mm) bulb is standard
  • Double braided copper capillary or stainless steel capillary
  • Numerous options: armour, duct flanges, compensated capillary, longer bulbs etc.
  • Other dial sizes available
  • Other bulb sizes available
  • 2% accuracy Vapour actuated
pro cons list
Pro / Cons List
  • Pro: Provide reliable indication and can be remote located away from process.
  • Pro: No Power required to operate process I.e. Temperature Switch/Recorder/Controller
  • Con: Expensive to manufacture, no longer mass produced
  • Con: Impractical if Gauge is located below Bulb,Need to be recalibrated.
bimetallic thermometers
Bimetallic Thermometers
  • Taken over Vapour filled market
  • Economical and Mass Produced
  • Vibration Sensitive
  • Accuracy 1%
bi metallic construction

Bi-Metallic Construction

Similar to a spiralhelic pressure gauge in its Construction

  • Basic Principle: Seebeck Effect
  • 1821… when two dissimilar wires are joined they generate a very small current/voltage potential
thermocouple management
Thermocouple Management
  • All connectors must be of the same type
  • All joints to be done with connectors that are rated fro the thermocuple type or else dissimilar metals will falsify the reading
  • Runs of less that 200 feet recommended
types of thermocouple design
Types of thermocouple design
  • Grounded type: Wires are welded to the casing. High (fast) response time but…susceptible to noise and eMF countershock.
  • Ungrounded type: Tip is electrically isolated by thin insulation so as not react electrically with any field power systems
  • Pro: less prone to burning out equipment
  • Con: slower reaction time( nominally)
internal construction
Internal Construction
  • Tubular : typical 1/4” diam to 3/8”
  • Micro tube 1/16” tube grounded
  • Standard is 1/4” with MgO filling inside the tube to prevent breakage of wire joint
  • P109 p120
rtd s
  • Typically design is ceramic rod with platinum wire wound around it.
  • Nominal resistance =100 ohms @0 Deg C.
  • Nominal accuracy= .1% !!
  • Does not require special “extension wire”
  • Overall much less installed cost.
  • Travel long didtance with 3rd wire
  • Self heating is minimal problem

100 deg c.

=185.51 ohms

Standard DIN Curve

Most Common

thermistors p127
Thermistors P127
  • Same idea but a lot higher ressitance range.
  • Works inversely of RTD ..decreases resistance as temp. increases
  • not as linear as RTD
  • Typical = 1000-10000 ohms
  • inexpensive = mass produced=everywhere in industry
  • I.e. motor windings
infra red sensors
Infra-Red Sensors
  • Based on the principle that all objects radiate energy….
  • Intensity of radiation increases as temeperature increases
  • Emissivity is best with blackened surfaces

Pro : NON contact

Safety:no risk

relavent accuracy



innacuracy from

surface finish

1% at best!!

profile for process use
Profile for process use

Connectors - Electrical connections can gradually loosen the connector, and generate heat as a result of repeated heating (expansion) and cooling (contraction), and/or dirt, carbon deposits, and corrosion. A noncontact thermometer quickly determines temperature increases that indicate serious problems.Electric Motors - To maintain lifespan of motors, inspect supply power connections and circuit breakers (or fuser) for equal temperatures.Motor Bearings - Detect hot spots and schedule repairs or replacements before problems lead to equipment failure.Motor Winding Insulation - Prolong the life of winding insulation by measuring its temperature.Phase-to-Phase Measurement - Check cables and connectors for equal phase-to-phase temperatures for induction motors, large computers, and other equipment.Transformers - Check the windings of air-cooled units for hotspots that indicate winding flaws.


Non-contact IR thermometers are quickly becoming an integral part of HACCP routines. Many food service professionals are familiar with the food safety procedure known as HACCP and which is now mandated for meat, poultry, and seafood production plants, as well as fruit and egg process plants. HACCP looks at the flow of food as it travels in and out of the Temperature Danger ZoneAlso Food and Drug Administration (FDA) suggests the use of infrared thermometers in the 1999 Federal Food Code, Annex 4, Section 8. and recognizes that quick scans of the surface temperature with an infrared thermometer facilitates general food safety:"The infrared thermometer quickly registers surface temperatures, which facilitates general food safety system surveillance by allowing the scanning of numerous food temperatures over a short period of time." MiniTempFS assures the greatest accuracy in the food critical zone called Danger Zone where harmful bacteria grow most rapidly. The term Danger Zone describes temperatures above 40°F (4.4°C) and below 140°F (60°C.) If potentially hazardous foods such as dairy products, shellfish, meats, etc., remain within this range for more than four hours, foodborne bacteria can grow. While precautions are taken and enforced by health and food safety inspections, the owners, operators, and service personnel bear every day responsibility of providing healthy quality food which means an awareness and plan of action to ensure foods are out of the Danger Zone.


Infrared Noncontact Thermometers Are Effective Equipment Performance Monitoring & Diagnostic ToolsNoncontact thermometers give you instant, accurate temperature readings of most key HVAC components. Diagnose duct leakage, supply and return air temperatures, plumbing lies, and other heat-related problems with infrared thermometers.Technicians quickly and efficiently gather temperature data from these applications:• Room Balancing: scan walls for unbalanced temperatures• Duct Work: scan the surface of ductwork to reveal temperature spikes and poor insulation• Steam Distribution Systems: diagnose blown or plugged steam traps from a safe distance• Furnace Performance: test furnace performance by checking the flue temperature• Supply/Return Registers: evaluate temperature differential between supply/return registersOther Applications:• Check for coil sweating of condensate lines• Check emergency relief value temperature• Scan wet wallboard for water leaks• Measure existing air from a coil and at a supply air grill

that s it for tonight
That’s it for Tonight!


Homework design 5 loops combination of pressure and temperature applications……..!

Next Week Process ControlPages 199-225

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