Protected: Summary of LecturesPreparation for final year examination

1) Chapter 1 (Questions 1 & 5)Problem 1 A temperature sensor has a transfer function of5mV/ C with an accuracy of + 1%. Determine the possible range of the transfer function. If a reading of 27.5 results from the sensor used.Determine the temperature that could provide this reading.

Problem 4 Assume that a particular temperature probe approximates first-order behavior in a particular application, that it has a time constant of 6s. If the probe is suddenly subjected to a temperature step from 75° C to 300° C. What temperature will be indicated 10s after the process has been initiated?

Problem 5Assume the same conditions as those in problem 4, but with step from 300C to 75° C. What temperature will be indicate after 10 s?

(a) Time response of first order type transducer. (maybe is like prob 4&5)

(b) Time constant of first order system (maybe is like prob 4&5)

(c) Modeling of thermocouple sensor with compensating circuit (Question 1)(prob 1 , maybe ?)

(refer to textbook chapter 2 & 11)(I give up on this)2) Chapter 2 & 3 (Questions 2, 3 & 4)

a) When the normal, t-test, Chi-square, and Thompson-Tau distribution tables will be used ?-The normal (or Gaussian) distribution function is a simple distribution function that is useful for a large number of common problems involving continuous random variable.-The t-distribution can be used to estimate the confidence interval of a mean value of a sample with a

certain confidence level for small sample sizes (less than 30).-it is also necessary to establish a confidence interval for the estimated variance. For normally distributed populations, a statistic called r (pronounced "kye squared") is used for the purpose of establishing a confidence interval.-The basis of these methods is to eliminate values that have a low probability of occurrence.

b) How to estimate uncertainty of instrument ?

c) How to estimate uncertainty in measurement ?

(another example 3 below, maybe?)

(refer to textbook Example 6.9 – 6.18)

Example 2 – Dta Analysis    Data Analysis-SolAnalysis of Experimental Data

• The increase in cost of living also affect the cost manufacturing of a tuna sandwich. A survey from 15 bakeries had been carried out and recorded the weights of the sandwich from the bakeries. The data shows average of the sandwich of 125g and standard deviation at 6.5g. If the allowable population of standard deviation is 8.6g

a) Determine the confidence interval that the bakeries are producing the sandwich within the allowable tolerance.

b) Evaluate the minimum standard deviation of the weight.

Example 3 – Uncertainty in Measurement   Uncertainty in Measurement-Sol

 Uncertainty in Measurement

• In estimating the operating temperature of an automotive engine, 10 samples are taken at rotational speed 2500 rpm and the temperature change of each sample is measured by a thermocouple. The measured values in degree Celsius are 85, 89, 90, 86, 88, 95, 92, 88, 93, 86. Evaluate

a) random uncertainty of each measurement.

b) random uncertainty of the mean of the measurement.

3) Chapter 4 (Question 2)

a) What is a wheatstone bridge ?

a simple circuit for measuring an unknown resistance/resistance change by connecting it so as to form a quadrilateral with three known resistances and applying a voltage between a pair of opposite corners.

b) What are the examples of signal conditioners?

-Amplification

-Attenuation

-Fitering (highpass, lowpass, bandpass, or bandstop)

-Diffrentiation

-Integration

-Linearization

-Combining a measured signal with a reference signal

-Converting a resistance to a voltage signal

-Converting a current signal to a voltage signal

-Converting a voltage signal to a current signal

-Converting a frequency signal to a voltage signal

c) What is the resistance and voltage relationships in a quarter arm wheatstone bridge?

d) Explain the function of the analog filters

An analog filter is any filter which operates on continuous-time signals. A lowpass filter allows low frequencies to pass without attenuation but, starting at a frequency fc called the corner frequency, attenuates higherfrequency

components of the signal. The frequency band with approximately constant gain (V0/Vi) between f = 0 and fc is known as the passband. A highpass filter allows high frequency to pass but attenuates low frequencies. A bandpass filter attenuates signals at both high and low frequencies but allows a range of frequencies to pass without attenuation.

e) What is the voltage ratio for the low-pass & high-pass filters ?

(refer to textbook Example 7.7 – 7.12)

4) Chapter 5 (Question 5)

a) What are the principles of PRT, Thermistor, thermocouple, thermopile, and pyrometer ?

-PRT (Platinum) is a thermally sensitive resistor that exhibits a change in electrical resistance with a change in its temperature. All metals produce a positive change in resistance for a positive change in temperature.

- The principle of work of thermocouple is based on Seebeck effect that is explained as a flow of current in a

closed loop of the metals. Dissimilar metals generate emf voltage across junction if at different reference temperatures.

-Thermopile is a serial arrangement of multiple thermocouples in one setting to reduce uncertainty.

-Thermistor is based on semiconductor expansion, highly nonlinear relation to temperature and negative slope due to electron behaviours uncertainty. Semiconductor reduces its resistance with increased temperature (similar to PRT)

-Pyrometer, without contact, temperature is measured by thermal radiation wavelength, thermal energy radiate and captured by photodetectors

b) What are the thermocouple laws ?

A thermocouple is pair of dissimilar metal wires that being joined at least at one end, which generate a thermoelectric voltage proportional to the temperature difference.

c) How to use thermocouples ? (no idea)

d) How to predict the time constant ? (no idea)

Slide have other easier example, better study it.

(refer to textbook Example 9.5 – 9.6 + lecture notes)

5) Chapter 6 (Question 6)

a) How to measure angle displacement?

Encoder, an accessory to a mechanical device that translates mechanical motion into a measurable electrical signal Digital or Analog (preferably digital).

b)Describe the types of optical encoders and point out their differences.

-Absolute Encoders: Digital data produced by code disk, which carries position information.-Incremental Encoders: Mechanical motion computed by measuring consecutive “on” states.

c) Explain the graycode and the binary codes in optical encoders.

-a pattern of light and dark strips is printed on to a strip and is detected by a sensor that moves along it

• the pattern takes the form of a series of lines as shown below

• it is arranged so that the combination is unique at each point

• sensor is an array of photodiodes

-binary code: if all bits were to change at about the same time: glitches

- One angle shift results in multiple bit changes.

-Gray code: only one bit changes at a time: no glitch

- only 1 bit has to be changed for all transitions.

d) Explain on how the resolution of encoders can be improved ?

increase the bit ? increase the cycle per resolution? Increase the number of lines on the disk?