Input-> processing-> output
This is the required block diagram for instrumentation system, you can understand from this that instrumentation system is something which takes the input, processes it and gives the output.
This is all. No need to write more than this in your exam.
The next will be about remote control system.
Remote Control System-:
Remote control system is a component of electronic device used for operating that device from a Line of Sight distance
Fig shows the block diagram of remote control system. I believe the topics are self-explanatory. You can just explain it by saying from power supply to timer and timer to infrared LEDs in transmitter section whereas, first in photo led, then op-amp, then counter and then load in case of receiver section. The next notes will be about the regulated power supply.
Regulated power supply-:
- The AC voltage is connected to the primary of the step-down transformer and is stepped down as desired.
- The rectifier circuit converts AC into pulsating DC.
- Then filter circuit converts pulsating DC into pulsating DC with few ripples than before.
- Then a regulated supply converts all these into a regulated DC output.
When a metal conductor is stretched or compressed, its resistance is changed on account of the fact that both length and diameter of conductor changes.
Not only resistance changes, there is also a change in value of resistivity of the conductor when it is strained ant this effect is called piezoresistive effect.
For an unstained gauge-:
Now, let us add a tensile stress be applied to the wire.
This causes the length to increase L+ΔL and diameter to decrease D-ΔD. (This is simple, why?)
Differentiating the above equation 1 wrote L, A, stress; we get;
∂R/∂S= ρ∂L/∂S-1/A²* ρL*∂A/∂S+L/A*∂ ρ/∂S——–(2)
Dividing equation 2 by R= ρL/A
(Dividing by R is multiplying by 1/R [confused! Heck don’t know what]) you can just solve this in your copy.
Resistance changes of following factors-:
Then let us discuss about the poison’s ratio
We know that poison’s ratio=r=Lateral strain/Longitudinal strain
Substituting this value to equation 4, we get;
1/R* ∂R/∂S=1/L∂L/∂S-2/D*(-) r∂L/L+1/ρ*∂ρ/∂S;
ΔR/R*1/R=ΔL/L+2rΔL/L+Δρ/ρ ;—-( 5)
Which is the required expression.
Then let us discuss about a factor called as gauge factor.
It is denoted by Gf (I don’t know if it’s Einstein’s GF or whatever LOL!!!It was a joke; I hope you didn’t understand it; as only I understand my jokes!!)
Gf= (ΔR/R)/ (ΔL/L);
(ΔR/R)= Gf*e (e=strain= (ΔL/L));
Equation 5(there is mismatch in equation number, but it’s done in order to make easy to understand, you can change if you like!)
Can be written as;
Gf* e=(ΔL/L)+2r*(ΔL/L)+ Δρ/ρ
Which is the required expression for gauge factor!
Then we will discuss about the principles of digital multimeter. I want to assure you that these types of notes are actually easy. But if you try to read them without leaving any words from book, then you will find a hard time. It is not possible to remember everything written in books, sometimes, even the writer doesn’t understand what he is writing. Things go same as we some students do while solving assignments. For some people, writing books is same as doing engineering assignments. And if the writer is a student who didn’t did assignment by himself, he is going to copy other text books. But if he copies other assignment, chances are very less that he will write a book though! So follow good books, but don’t follow books.
Figure above shows the block diagram of digital multimeter.
What you are going to write in your copy is so simple. Just try to remember the block diagram. Then write like this; to measure ac voltage, first ac voltage is passed to caliberated attenuator ant hen to converter then to adc(it does analog to digital) then to decoder and finally get the output.
Likewise for dc current; you’ll write like this. First dc current sent to shunt, then to precision ac/dc converter then to adc(analog to digital) then finally to decoder and then to output.
I must say that you can now, write about everything else.
Now, let us discuss about the another thing called as transducer-:
Transducer is an electrical instrument used for converting the non-electrical quantity into the electrical quantity.
So, we can also call transducer as device to convert energy from one form to another form.
For eg-: many physical parameters such as heat, pH value, humidity, intensity of light, are converted into electrical form by the help of transducer.
Now, move onto the next part called as;
Classification of transducers-:
Transducers can be classified as follows-:
- As based on transduction form used
- As primary and secondary transducer
- As passive and active transducer
- As analog and digital transducer
- As transducer and inverse transducer
Mnemonic to remember all these-: Passive Analog signal is inverse transduced in a primary signal.
- As based on transduction form used:
On the basis of principle of transduction, transducer are classified as resistive, inductive, capacitive etc.
- As primary and secondary transducer
A transducer is said to be primary transducer if there is only one stage of transduction. For eg-: Bourdon tube.
But a transducer is said to be secondary transducer if there are more stages of transduction.
For eg-: LVDT (Linear Variable Differential Transformer)
- Passive and active transducer
Passive transducers are those that derive the power required for transduction from auxiliary power source. Eg-: resistive, inductive, and the capacitive transducers.
Active transcoder are those which don’t require an external power source to produce their output.
For eg-: thermocouple and piezo-electric crystal etc.
- Analog and digital transducer-:
Analog transducers are those transducers that convert an output quality into an analog output quantity, which is a continuous function of time.
For eg-: strain gauge, thermocouple, LVDT etc.
And digital transducers convert into digital.
- Transducers and inverse transducers:
Transducers converts non-electrical quantity into electrical quantity and
Inverse transducers converts electrical quantity into non-electrical quantity.
Then we are in a position to discuss about the advantages of the transducers. For that we can describe their advantages as follows.
- Friction is minimized.
- Mass-inertia effect is minimized
- It gives Electrical output, which, can be easily processed.
Now let us discuss about the data logger-:
Actually data logger is something, the name says itself. Something that helps to log all the data, i.e to save data for future reference.
Clearly, you can see from the block diagram, that, the programmer is alerted by a real time clock (think that it is an alarm clock). Then, what happens is that, an input comes. It gets scanned by input scanner and then the signal amplifier amplifies it, conditioner conditions it. Then if the input data was in analog form then it will be converted into digital form by the help of analog to digital converter. Finally these information’s are recorded by help of recorder.
Things will go really easy in this chapter if you try to write in a to the point form. I mean to say that you write the definition, make a figure, if there are equations; you write them, and then; explain a little bit. You can get full marks in this question like this. So instead of trying to remember things, try to understand a point about it and explain that point in detail.