Measurement Instruments Flashcards
Def : absolute zero
The moint at which molecular movement stops
This is for?
Each stands for?
Answer 1
Def : boiling point
The point at which the vapor pressure of a liquid equals the atmospheric pressure resulting in the transition from liquid to gas
This is for?
Components?
This is for?
Components?
When 2 bodies make contact what happens? (Thermal)
4 types of thermowells?
-threaded
-flanged
-vanstone
-welded
What should you put between the sensor and thermowell?
Heat transfer compound ie thermal conductive grease
Def : 1 thermal time constant
How long it takes to get from 0 to 63.2% of the final temp
What is the minimum recommended immersion length of a thermowell
6 x diameter
When you require a thermowell in a small pipe what are the 2 mounting options
- 45 degree with tip pointing into the flow
- on an elbow with rip pointing into the flow
0 degrees Kelvin is
-273.5 ‘C
0 degrees Rankine is
- 459.67 ‘ F
If you are calculating linear expansion and copper 16.6/ degree C you multiply that by :
10^-6
Thermometer A is ?
Total immersion
Thermometer B is
Partial immersion ( to immersion mark)
Thermometer C is?
Complete immersion
How do you avoid parallax errors?
Look at straight on
Thermometer class 1
Liquid other than mercury
Thermometer class 2 is
Liquid-vapour interface
Thermometer class 3 is
Gas filled
Thermometer class 5 is
Mercury
Def : head effect error
When the bulb is high and capillary is low the pressure from capillary cN cause error
In a thermometer an invar wire is used for
Temp compensation in a mercury system
Thermometer: 2 for case compensation
2 capillaries or
What thermometer classification has the highest range
Class 3
Type E thermocouple colors
Purple
With thermocouples the ____ wire is always -
Red
Thermocouple type j colors
Conductor : white
Jacket : black
Thermocouple type k colors
Conductor : yellow
Jacket : yellow
Thermocouple type R colors
Conductor: black
Jacket : green
Thermocouple type S colors
Conductor: black
Jacket : green
Thermocouple type T colors
Conductor : blue
Jacket : blue
A is
Reference junction, where the thermocouple wires are connected to cable could be in a jb or wherever
ICE point (rtd)
@ 0’c it has X ohm res
What is the most widely used and most linear material for rtds
Platnum
What is the difference between industrial grade and lab grade platinum rtds
Industrial 100 ohm ice point
Lab 25.5 ohm ice point
Rtd European coefficient platnum
.003850 ohms/ohm’C
Rtds most common errors
- lead wire resistance
- self heating
- strain effect
What is a b c
How does a thermistor work
Very high ( 2 to 10k) ohm ice point that goes down as temp goes up
Thermistor disadvantages
Limited temp range -101 to 300
Not linear
LRV ma?
URV ma?
Absorption for black body vs highly polished surface? Reflection?
I for black body , 0 for high polished
Opposite for reflection
This is
What is D/S (pyrometer)
Distance / spot ratio for pyrometer
What is D/S (pyrometer)
Distance / spot ratio for pyrometer
How does flow leak detection work?
If flow quantity at 2 points is different then there is a leak
This is for
Process flow rate
Qm = flow rate
Qvs = volume of flow
ps = density
Def : accuracy
How close an indicated value is to a recognized and accepted standard value ( ideal value)
Def : differential pressure
Pressure difference between 2 points
Def : head meter
A differential pressure measurement device
Def : integrator
A device that adds up the value of a quantity over a given amount of time
Def plainmeter
A device that measures the area of a plane surface by tracing its perimiter
Def : pressure head
The internal energy of a fluid due to its pressure
Def : primary element
The first element that responds to the measured variable
ie flow sensor
Def : range
The region between the limits within which a quantity is measured
Def rangeability
The relationship between the range and minimum quantity that can be measured
Def : rate meter
A flow meter that indicates flow rate as a fluid passes through the meter
Def : 2ndary element
A device that receives the primary flow elements signal and converts it to a standard control signal
Ex : I/P transducer
Def : span
The difference between the upper and lower range values
This is? It’s range?
This is? It’s range?
Turbulent
This is? It’s range?
Transitional
This is ?
Reynolds #
What is pulsating flow?
Irregular or repeating variations in fluid flow rate
What is damping?
The progressive reduction or suppression of oscillations in a device or system
Piston type dampers aka
Snubbers
Snubbers do :
Delay the signal to the differential pressure element to prevent pressure spikes
Sintered metal pulsation dampers are:
Use mesh loking material to slow pressure spikes from the primary element
A ____ orifice plate should be used with a low Reynolds #
Quadrant
2 ways to reduce pulsations
- move flow meter away from pulsation source
- install filters / hardware dampening devices
What is the advantage of a class 2 liquid/vapor temp system
Does not require ambient temp compensation
These are
U tube manometer
This is a
Mechanical differential pressure indicator
What do bellows differential indicators need due to temp effects on the bellows
Ambient temp compensation
What kind of diff pressure switch would you use for high pressure?
Piston
What does a pneumatic differential pressure transmitter do?
Sends a 20 to 100kpag or 3 to 15psig signal thats proportional to the measured diff pressure
What does an electronic differential pressure transmitter do
Sends an electronic signal ( usually 4-20) that is proportional to the measured diff pressure
What are the 2 types of transducers?
- strain guage: creates a diff in resistance when bent length ways
- capacitance: changes distance between 2 plates
This is in WC
6
On a capacitance pressure transducer if you increase the distance between the plates the capacitance _____ ?
It goes down
This is?
This is?
These are? Uses?
Used with low reynolds # ( laminar flow)
These are? Uses?
Upping viscosity causes what with the Reynolds #
Reynolds goes down
🔺️ p to Q you ?
Ie convert diff pressure to flow
Square root
Q to 🔺️p you
Ie convert flow to diff pressure
X^2 it
