Electronics?

[petersonra]

100512-2220 EST

How does a straingage transducer work to measure force or torque?
Why would you need to know this? What you need to know is what signal levels to expect for what levels of force. worrying about how that signal is generated is silly. No one except the people that make them ever need to know all that much about this kind of thing, other than in a very general way.

With what voltage levels are you concerned in this application? How does the speed of a permanent magnetic brush type DC motor relate to the applied armature voltage? What methods can you use to measure the current to this motor?
"Black box" kinds of things.

How does an LVDT work? What is the output impedance of an NPN transistor with a collector resistance of 5.6 k ohms?
Stuff you will never use.

Why is aTTL output better?
The answer is that it's not better, it's just different. But it's also not relevant to anything most electricians, or engineers for that matter, will ever deal with.

How does an operational amplifier work and what can you do with it? What is a constant current source and its limitations? How can you make one? In the AC position what does a Simpson 260 meter read? If you measured a sine wave source with the Simpson how would you calculate the power dissipated in a 100 ohm resistor? Now change the source to white noise and the same question? If you suspect the your AC voltmeter is not calibrated correctly, then how can you use a diode and a known good DC meter to check it? And on-and-on.
More stuff no typical electrician would ever use.
.

You have to focus on learning things you actually need to know to do your job. Other stuff may be fun and interesting, but fun and interesting has to be a much lower priority than knowledge and skills you actually need. I think the instructor is handling this as kind of a survey course, and that seems to me to be appropriate for a basic electrician type class.

If you want to make the leap to instrument technician, then you need more electronics training. In some plants, at least some of the electricians often function as de facto instrument technicians, but you will need more than one class of real basic electronics at that point.

 

[SegDog]

Stupid is....

Stupid is....

I've spent the greater part of five decades working with a large percentage of people who did not want to learn more than they need to for minimum performance.

When I worked in government jobs, many would not learn unless someone else was paying for the training.

This explains the sad state of affairs that we have in our culture.

 

[petersonra]

I've spent the greater part of five decades working with a large percentage of people who did not want to learn more than they need to for minimum performance.

When minimum performance is all that is ever expected and there is no incentive to go beyond that, it is not surprising that a large percentage of people would do the minimum. In many cases, managers active discourage people from improving themselves beyond the bare minimum, as they do not want people to become more valuable, or to become a threat to the manager's supposed expertise, which is often a lot less than generally supposed.

When I worked in government jobs, many would not learn unless someone else was paying for the training.

Government jobs are that way. it's just the nature of the beast.

This explains the sad state of affairs that we have in our culture.

Perhaps some of it.

 

[mtfallsmikey]

When minimum performance is all that is ever expected and there is no incentive to go beyond that, it is not surprising that a large percentage of people would do the minimum. In many cases, managers active discourage people from improving themselves beyond the bare minimum, as they do not want people to become more valuable, or to become a threat to the manager's supposed expertise, which is often a lot less than generally supposed.

Government jobs are that way. it's just the nature of the beast.

Perhaps some of it.

Amen brother!!!....That statement is true. I've always tried to share my knowledge (limited!) with others, few are responsive, most feel insulted....I was taught to work smart, so you wouldn't have to work hard....But, oftentimes there is incentive to do better, you will get noticed and promoted, but that is not the norm.

 

[gar]

100514-0738 EST

petersonra:

This thread started out with a two part question. One part related to an "industrial electrician". This can mean many things, but in many plants today there are many machines highly dependent upon electronic circuits and related items. A broad basic understanding of the components and system can greatly assist one in troubleshooting problems.

I won't make comments on each of of your comments on my post except for one.

What is the output impedance of an NPN transistor with a collector resistance of 5.6 k ohms?
Stuff you will never use.

Why is a TTL output better?
The answer is that it's not better, it's just different. But it's also not relevant to anything most electricians, or engineers for that matter, will ever deal with.

Your response indicates you do not understand the difference.

In a circuit with a transistor and a pull-up collector resistance the output impedance when the transistor is off is the impedance of the resistor. In my example 5.6 K. When the transistor is on its output impedance is determined by the saturation characteristics of the transistor. For a 2N4400 it is maybe 0.5 ohm. Think about what this means in terms of noise immunity in the two different states.

In contrast consider a "totem-pole" TTL output. What does TTL represent? Transistor Transistor Logic. This type of logic as represented by TI 5400 and 7400 series devices consists of both a pull-down transistor and a pull-up transistor. Some early TTLs did not have the "totem-pole". By replacing the pull-up resistor of RTL (Resistor Transistor Logic) with an active pull-up transistor the output impedance in the high state is greatly reduced compared with a simple resistor pull-up. Thus, the TTL logic output has greater noise immunity than does an equivalent RTL gate. It was the mid 1960s when these TI devices became available, and somewhat inexpensive by about 1967-8. TI made a big issue of the improved noise immunity of the 5400/7400 series. Another factor is the faster rise time with an active pull-up.

http://en.wikipedia.org/wiki/Logic_gate
http://en.wikipedia.org/wiki/Transistor–transistor_logic

.

 

[petersonra]

I actually do have a vague clue of the difference between an OC and a TTL output.

Is a 5V TTL signal more noise immune than a 24V OC signal? Not in my experience.

OC outputs have a wider range of applicability than TTL does. making them "better".

If you are stuck with TTL level signals, a TTL output might well be better for that narrow application.

But generally, TTL level signals don't belong in an industrial environment if they can be avoided, certainly no where a typical electrican would access them.

In any case, the average electrician is not going to be deciding whether to design a circuit with TTL or OC. He will be replacing a black box with another black box.

 

[gar]

100514-2103 EST

petersona:

The original post question was why a knowledge of electronics might be important and you are try to say it is unimportant.

Back to your last response. A 200 ft run of a wire pair thru a noisy environment may have better noise immunity when driven from a 24 V system with a resistor pull-up compared to a totem-pole at 5 V or it may not. Your experience says it does and I might agree depending upon some factors. But you miss the point of having an understand of the circuits.

If you use a totem-pole driver at 24 V signal levels, and a 12 v threshold detector at the destination, then the totem-pole system will be better than the the resistor pull-up system at that same voltage level and the use of a practical pull-up resistance value, meaning reasonable power dissipation.

In another thread a person had a problem with a device that operated improperly. I believe this may have been at a 24 V level with a resistor pull-up at the receiving end and a switch contact at the input end. This is a high impedance in one state (switch open), and a low impedance in the other state (contact closed). The problem was most likely capacitive coupling into the signal line when the contact was open. If one understands some electronic concepts, then one solution is to have the equivalent of the totem-pole design. Basically a SPDT switch at the input so that two low impedance discrete states exist at the input.

Changing black boxes will not always easily solve a troubleshooting problem. If you understand the theory of the system, then you are probably in a better position to more quickly find the problem.

.

 

[SegDog]

missing the point...

missing the point...

Presently, I work with a person that is compelled to make a comment about every statement that I make no matter how dumb their comments are!

Once I received a promotion and the minority board member protested my promotion on the grounds that my outside night classes, outside certification work, and outside extra-curricular activities should not have been considered for the promotion. The protest was rejected on the grounds that indeed every aspect of the job involved self-initiation, self-motivation, and the ability to work without direct supervisor.

I hope that those who miss the point wakeup before it's too late.

 

[LarryFine]

Presently, I work with a person that is compelled to make a comment about every statement that I make no matter how dumb their comments are!

You get used to that around here.

 

[LHarrington]

good afternoon,

Here where I work having a general knowledge of electronics has improved my troubleshooting skills as a Industrial Electrician. I was very fortunate to has some great instructors in Trades college. It also has opened the doors to a lot of challenging projects that involved intricate electronic component. Being a more versatile electrician has opened a lot of doors to better finances. I would high recommend you look for a better instructor including hands on applications. Make sure you let the current education facility know your feelings so no one else need to go through the wasted time and money.

LHarrington

 

[dutchparson]

It depends on the job, some jobs you can skate by without any electronics knowledge, some will require it. No matter what your job is understanding electronics and the theory will make you better at your job.

Personally I would never hire someone without a strong theory background and I think your instructor should find a new line of work.

I definitely agree with you