The basic activity of students In a semiconductor lab is to investigate IV curves of basic semiconductor elements (diodes, transistors, etc.). They can do it in various ways.
The most primitive (for specialists) way is to change manually the input electrical quantity, then to measure the output quantity by digital multimeters, after - to fill the data in a table, and finally - to plot the IV curve. It is painful, old-fashioned and requires a lot of time. I have illustrated it in the first picture and the link to a movie below (I made them yesterday evening in the laboratory; the quality is not so perfect:)
https://drive.google.com/open?id=0B45uRPpHPD9hOHhDTWEyWjJPcVE
(Manual investigation of Si diode)
It seems the most perfect (for specialists) way is students to explore IV curves fully automatically - by a kind of a curve tracer. Thus they will instantly solve the problem in a modern way and will use the released time for something more useful. I have illustrated it by the Microlab system equipped with an additional periphery (cascaded V-to-I and I-to-V converters):
https://drive.google.com/open?id=0B45uRPpHPD9hX01tUmRSX3hvMUk
(Automatic investigation of LED by current)
https://drive.google.com/open?id=0B45uRPpHPD9hRTU5VVBXS1p0ZGs
(Automatic investigation of 3.3V zener diode by current)
But perhaps, for educational purposes, the truth is somewhere in the middle - to examine the IV curve step by step? Thus students can become familiar with each interesting section of the characteristic:
https://drive.google.com/open?id=0B45uRPpHPD9hRzVYVXNteUJjTGM
(Semiautomatic investigation of Si diode by voltage)
https://drive.google.com/open?id=0B45uRPpHPD9hMTZkbnNJT0pBTWM
(Semiautomatic investigation of Si diode by a digital oscilloscope)
See also:
https://www.researchgate.net/post/How_do_we_investigate_semiconductor_devices_in_the_educational_lab
https://www.researchgate.net/post/How_do_we_investigate_the_IV_curve_of_a_forward_biased_diode-by_current_voltage_or_real_source
Cyril, i don't think the fully-automated investigation of such simple circuits is a good idea because i'm not sure the students will understand the basics. It's important that student understand that by changing the current/voltage of nonlinear elements, their resistance changes as well.
If the experiment is carried out the old fashioned way then the students will be able to build the V-I characteristic and then to calculate the static resistance for a couple of operational points.
On the other hand an example for semi-automated experiment would be if you power up the circuit with a waveform (sinusoidal or triangular) and observe the result on the oscilloscope. But in my opinion such experiment should only be conducted after the students draw their V-I characteristics manually.
Boris, as I can understand your idea, all the level of investigation are useful if only we keep the right down-top sequence (manual, semi-, fully-automated)?
The picture below illustrates your last suggestion - "to power up the circuit with a waveform (sinusoidal or triangular) and observe the result on the oscilloscope".
Indeed. It might be useful to automate the investigation once the students are familiar with the basics. In other words when you want to demonstrate a certain application of that device/element. For example once the students understand how nonlinear elements behave, they could see what a rectifier does. But not before that.
Exactly, Boris! Because I see that you have interest in psychology and teaching methodology, I want to share one more secret that I found myself in all these years as a teacher. It is a pity that, in principle, this should be the work of psychologists and educators in universities ... but they are so sterile and far from real life that we, humble engineers, need themselves to rediscover the truth...
My observation is that, regardless of how the student explores the IV curve of the element (manual, semi-automatic or fully automatic), he/she must see (and possibly guide) the development of the process, point by point, on the screen (as in the movies above)... have the feeling that he/she "moves" along the characteristic. Thus, through these psycho-motor reactions, he/she will create a lasting notion of the behavior of the investigated element.... will begin to "feel" it... This is not only my idea (although I would like to be so:); this idea is proposed by Seymour Papert and implemented by his Logo Turtle.
And a word of advice to you - do not delve too much in the pedagogical, methodological and psychological side of teaching; instead, focus on the technical (real) part of teaching, and make every effort to solve the problems there.
I will support this tip with a little story of my life. In 1990 (the beginning of "perestroika" in the country), I was enthusiastic about the pedagogical and methodological side of laboratory activities. I started doing a doctoral thesis on the use of computers for automation of educational laboratory experiments (then I created the Microlab system). But unfortunately just then they closed the Department of Education and my endeavor failed. Then I was angry, but later I shifted my attention to revealing basic ideas behind circuits... and I did a thesis related to this topic.
Hello Cyril
The Very straight forward answer to your question is -MANUAL.
I agree with Boris and if you refer to my response to your other question, it is not only the objective of obtaining the characteristics curve but more of UNDERSTANDING as HOW THE DEVICE WORKS. And particularly in Analog electronics, understanding of the fundamental behavior of diodes and transistors (both BJTs and FET/MOSFETs) is A MUST which later proves to be VERY CRITICAL when working on complex circuits and signal systems.
You can use the automated methods in the classroom to demonstrate quickly the difference between characteristics of various diodes such as ordinary rectifier, Zener, LED, Schottky etc. But when it comes to experiments, LETS DO IT MANUALLY.
Again, in automatic systems the students will focus on obtaining the Curves and loose sight on the working of the device.
Finally Cyril, the last part/para of your response above states the condition of an AUTOMATED EFFORT! No need to say anything further. You have made excellent observations!!!
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