ATPL (A)
Review Worksheets
022 INSTRUMENTATION
BY KDMN
2020
,I/SENSORS AND INSTRUMENTS
01 PRESSURE GAUGES
a) DEFINITIONS:
Absolute Pressure AP: zero-referenced against a perfect, using an absolute scale.
➔ AP = Gauge Pressure + Atmosheric Pressure = Pg + Po
Gauge Pressure Pg : zero-referenced against ambiant air pressure.
Differential Pressure ΔP is the difference in pressure between 2 points.
b) UNITS:
Pascal (Pa), SI unit : N/m² 1 bar = 10 000 Pa
Bar (bar) 1 PSI = 0.07 bar
Inches of Mercury (inHg) 1 013.25 HPa = 14.7 PSI = 29.92 inHg
Pounds per Square Inch (PSI)
c) SENSORS:
Types of Measured In/for which Pictures
sensors Pressure devices
Diaphragms Low pressure •Altimeter
(0.1 to 50 •ASI
PSI) •Machmeter
Bellows •Medium • Fuel
(connected pressure (up Pressure
diaphragm to 50 PSI) gauge
chambers) •Differential
Pressure
Aneroide • Absolute • Low
Capsule Pressure pressure fuel
(sealed pump
diaphragms) • MAP
,Bourdon • High •Engine oil
Tube pressure Pressure
(500 to • hydraulic
3000PSI) pressure
02 TEMPERATURES
a) UNITS:
Celcius (°C) T°C = (T°F -32) x 5/9
Fahrenheit (°F)
Kelvin (K) TK = T°C + 273
b) SENSORS:
Type System Principle Other
Expansion •Bimetallic 2 different metals
• up to 60°C having different
thermal expansion
coefficients
Electrical •Electrical • Based on the
Resistance Wheatstone bridge
Thermometer • linear fonction of
(ERT) voltage
• up to 150 °C
Electrical Ratio Meter • used for engine oil
ERT temperature
Electrical •Thermocouple • electromotive force • Used to measure Cylinder head
• up to 540°C is created due to a Temperature
difference of
temperatures • for turbine engine we use chromal/alumel
between Hot source for the metals
and Cold Source
(constant)
, 03 FUEL GAUGE
a) UNITS:
Kilograms (Kg) 1Kg = 2.204 lbs
Pounds (lbs)
Liter (L) 1USG = 3.786 L
US gallon (USG)
b) SENSORS:
Types Advantages Disadvantages Principles
Electrical float gauge Easy to build •Inaccurate • DC powered
•Varying with • gives Volume
Temperature
Capacitance gauge • temperature, • wrong value if • AC powered
altitude, acceleration water in the tank • value deponds on
do not affect the nature of the
dielectric and density
04 FUEL FLOWMETER
a) INTRO:
• used to monitor fuel quantity
• inserted between High pressure Pump and fuel injector on jet engines
b) UNITS:
Liters per hour (L/h) US gallons per hour (USG/h)
c) SENSORS:
Types Principles Pictures
Volumetric Composed by a
flowmeters turbine rotor with a
magnet which creates
pulses with the
passage of the liquide
Review Worksheets
022 INSTRUMENTATION
BY KDMN
2020
,I/SENSORS AND INSTRUMENTS
01 PRESSURE GAUGES
a) DEFINITIONS:
Absolute Pressure AP: zero-referenced against a perfect, using an absolute scale.
➔ AP = Gauge Pressure + Atmosheric Pressure = Pg + Po
Gauge Pressure Pg : zero-referenced against ambiant air pressure.
Differential Pressure ΔP is the difference in pressure between 2 points.
b) UNITS:
Pascal (Pa), SI unit : N/m² 1 bar = 10 000 Pa
Bar (bar) 1 PSI = 0.07 bar
Inches of Mercury (inHg) 1 013.25 HPa = 14.7 PSI = 29.92 inHg
Pounds per Square Inch (PSI)
c) SENSORS:
Types of Measured In/for which Pictures
sensors Pressure devices
Diaphragms Low pressure •Altimeter
(0.1 to 50 •ASI
PSI) •Machmeter
Bellows •Medium • Fuel
(connected pressure (up Pressure
diaphragm to 50 PSI) gauge
chambers) •Differential
Pressure
Aneroide • Absolute • Low
Capsule Pressure pressure fuel
(sealed pump
diaphragms) • MAP
,Bourdon • High •Engine oil
Tube pressure Pressure
(500 to • hydraulic
3000PSI) pressure
02 TEMPERATURES
a) UNITS:
Celcius (°C) T°C = (T°F -32) x 5/9
Fahrenheit (°F)
Kelvin (K) TK = T°C + 273
b) SENSORS:
Type System Principle Other
Expansion •Bimetallic 2 different metals
• up to 60°C having different
thermal expansion
coefficients
Electrical •Electrical • Based on the
Resistance Wheatstone bridge
Thermometer • linear fonction of
(ERT) voltage
• up to 150 °C
Electrical Ratio Meter • used for engine oil
ERT temperature
Electrical •Thermocouple • electromotive force • Used to measure Cylinder head
• up to 540°C is created due to a Temperature
difference of
temperatures • for turbine engine we use chromal/alumel
between Hot source for the metals
and Cold Source
(constant)
, 03 FUEL GAUGE
a) UNITS:
Kilograms (Kg) 1Kg = 2.204 lbs
Pounds (lbs)
Liter (L) 1USG = 3.786 L
US gallon (USG)
b) SENSORS:
Types Advantages Disadvantages Principles
Electrical float gauge Easy to build •Inaccurate • DC powered
•Varying with • gives Volume
Temperature
Capacitance gauge • temperature, • wrong value if • AC powered
altitude, acceleration water in the tank • value deponds on
do not affect the nature of the
dielectric and density
04 FUEL FLOWMETER
a) INTRO:
• used to monitor fuel quantity
• inserted between High pressure Pump and fuel injector on jet engines
b) UNITS:
Liters per hour (L/h) US gallons per hour (USG/h)
c) SENSORS:
Types Principles Pictures
Volumetric Composed by a
flowmeters turbine rotor with a
magnet which creates
pulses with the
passage of the liquide
