Lesson 7: Temp Measuring Flashcards
Purpose of Temp. Measuring Instruments?
– engine performance and health
– liquid temperatures (fuel, hyd. Fluid) for condition monitoring
– outside air temperatures for airspeed/ aircraft performance calculations
– Monitor health of avionics systems
Range of cylinder head temp?
200F to 475F
What type of mixtures give low cylinder head temp?
Excessively rich
Excessively lean
What is the desired oil temp. range?
75F to 245F
What are the factors affecting thrust?
Temp. and Altitude
What do temp. indicators measure?
the AMOUNT of temp. changes
electrically/monitored
Effects of temp. on a substance?
- Expansion (solid/liquid)
- Vapour Press. (Liquid/gas)
- Electrical Resist.
- Electromotive force (btwn junctions)
What instruments do we use to measure temp?
Expansion type
Vapour pressure type
electrical type
Which is the most common system used?
Electrical type
Describe the Gas Expansion Type Sensing?
Liquid in a bulb
high temp = high vapour press = straightens bourdon tube = increase temp indication
What 2 methods are used for electrical type sensing?
Variable Resistance (wheatstone/ ratiometer) Thermoelectric
How does the wheatstone variable resistance work?
electrically powered
3 fixed resist and 1 variable, and a moving coil indicator (galvanometer)
Alters current flow
How does the Ratiometer work?
electrically powered
variable/fixed resistor + moving coil indicator (galvanometer)
How does thermoelectric sensing work?
Independent of Airc.Power
For engine temp
has a THERMOCOUPLE and MOVING COIL
DISSIMIALR METALS = hot/cold junction
CHT probes use what metals?
Iron and Constantan
