thermistor Flashcards
Function of thermistor for incubators
Used to ensure the temperature in the incubator is perfect
Automatically alerting staff if the temperature falls outside of a predetermined range
Why are thermistors good for monitoring temps in incubator
They are sensitive enough to precisely monitor temps in incubator for premature babies.
What does it mean that some semiconductors have a negative temperature coefficient
Their resistance drops as temperature increases
Why do some semiconductors have negative temp coefficient
As temperature increases, number density of charge carriers also increases.
What is a thermistor,whats it made out of, and a property of it.
electrical component made from a semiconductor with a negative temp coefficient.
Why are thermistors particularly very useful in temperature sensing circuits
Because as temperature of thermistor increases, resistance of thermistor decreases.
Therefore a small change in temperature can be detected by monitoring resistance of the thermistor.
ie. if temp up, resistance down, u can see by using ohmeter.
What are the 5 uses of thermistors.
- Simple thermometers
- In thermostats to control heating and air conditioning units
- to monitor temperature of components inside electrical devices eg. computers. So that they can power down before overheating damages them
- Measure temperature in wide variety of electrical devices eg. kettle/fridges
- To monitor engine temperature to make sure engine does not overheat
Is the graph of resistance and temperature for thermistors linear or non linear.
and what kind of a decrease at start and as it gets hotter and hotter
non linear ie. CURVE
significant decrease at start and gradual drop as it gets hotter and hotter
3 IV characteristics of thermistor
resistance not constant
non ohmic conductor as doesnt follow ohms law
behaves same way regardless of polarity
What is the crucial difference in terms of IV characteristic for thermistor and filament lamp
For a filament lamp, electrons transfer energy to positive ions, increasing temps and thus increasing resistance.
With thermistor, same as filament lamp, as current increases the temperature increases. But this temperature increase leads to a drop in resistance because number density of charge carriers increases.
Can be confirmed by measuring V/I at various points in graph.
An increase in temeprature leads to an increase in the number density of free electrons. Which means resistance of thermistor decreases as temperature increases.
What equipment needed for an experiment to measure resistance of thermistor as temperature changes?
thermistor
ohmeter
water bath
Why is a thermistor selected for the experiment of temp and resistance?
to ensure it provides the greatest change in resistance over the range of temperatures in which it will operate.
meaning thermistor has the capability of having a large range of resistances, in order to compare results.
