Deck 3: Sensing 2

Question 1

Give two examples of ways to fail in getting clear signals from you sensor ( in this case an ammeter )?

Answer 1

1) High resistance source and low reistance detector.
2) Source that has small e.m.f and an insensitive detector.

Question 2

Give two examples of ways of getting good signals from sensors.

Answer 2

1) Use a high reistance detector
2) Use a measurement amplifier or more sensitive detector.

Question 3

Define resolution

Answer 3

The resolution of a sensor is the smallest charge that the sensor can detect in the quantity it is measuring.

Question 4

Define sensitivity

Answer 4

The sensitivity of a measuring system is the ratio of change of output to change of input.

Question 5

Response time

Answer 5

The response time is the length of time a sensor takes to reach its final reading following a sharp change in input.

Question 6

Why do you place an ammeter in series in a circuit?

Answer 6

So that the current through the ammeter is the same as the current through the component.

Question 7

What is power defined as?

Answer 7

Power is defined as the rate of tansfer of energy.

Question 8

Draw the I/V graph for a filament and explain the graph.

Answer 8

• The reason the graph curves like so is because the resistance of a metal increases as the temperature increases. Due to the fact that the ions vibrate more.

Question 9

Draw the R/Temp graph for a thermistor and explain it.

Answer 9

• For a thermistor as the temperature increases the resistance decreases.
• Warming the thermistor gives more electrons enough energy to escape from their atoms. This means that there are more charge arrier available.

Question 10

Draw the I/V graph for a diode.

Answer 10

• Diodes only let current flow in one direction.

Question 11

Explain how the e.m.f and internal resistance of a battery can be calculated using the following circuit.

Answer 11

• By changing the value of R(load resistance) in this circuit and measuring the current(I)and p.d(V) you can work out the internal resistanceand e.m.f using(and plotting on a graph) :

V= E - Ir where E is the y-intercept and -r is the gradient.

Question 12

What is an easier way to measure the e.m.f of a power source?

Answer 12

An easier way is to connect a high-resistance voltmeter across its terminals. A small current will flow through the voltmeter, so there must be some lost volts. This means you will measure slightly less than the actualy e.m.f.

Question 13

What is the potential divider equation?

Answer 13

Vout= R1/R1+R2 x Vin