Interview Questions

Mr_B

Member
Join Date
May 2005
Posts
79
Hi Guys. We r interviewing sum electrical guys and wud like 2 c if they hav a background in PLC's. Just the basic faultfinding and small program changes. No specific PLC though.

Wud u guys help me out with a few questions.
 
What is a PLC, and what does it do?

Name three types of PLC's.

What is the most common method used in PLC programming.

Name to other types of PLC programming.

Name three types of input cards.

Name three types of output cards.

Can a 4-20 ma analog input card be used on a 0-10 volt signal?

Can a 0-10 volt analog input card be used on a 4-20 ma signal.

How many outputs are needed to control a 1/10th hp 480 volt three phase motor?

Draw a simple AND input ladder.

Draw a simple OR input ladder.

Draw a simple NOR input ladder.

Draw a circuit with a NO input and NC input to latch a relay coil.

Draw a simple circuit, using a 480vac signal and a 24vdc input card, and a resident smoke timer.

Name 5 different uses for a PLC.

Draw a simple stoplight program.

Draw a one shot or a flip-flop ladder diagram.

How do you lengthen scan time?

Why would you use online programming or editing?

Can two output coils have the same address?

regards.....casey
 
Last edited:
Communication protocol

Previous experience with bussytems-- Profibus,DeviceNET ect.

Previous experience with interfacing to HMI/SCADA-- Citect,Intouch,UniOP ect.

Regards
 
Ask them to write a flip-flop using whatever PLC ladder logic they are familiar with.

If there is a 250 ohm resistor across the terminals of an analog signal, what would that mean to you?
 
Last edited:
If you do not have people in house that are experienced in electrical and plc then you may want to find an employment agency, especially if they specialize in technical, to assist you.

Another option is to purchase "tests" designed for the specific job. Example: http://www.totaltesting.com/industrialskillstests.shtml
There are others and a technical employment agency could assist you with this too.

If the above is not an option then you may have to rely heavily on his stated "verifiable" experience. The problem with questions you may ask is that you dont know the answers. If the position is not for a full time programmer but more for electrician with plc skills then worry about the electrical part the most.

Anyway I ask people for electrical and plcs to draw a holding circuit in relay logic and ladder logic for motor control, you would not believe how many can not do this. In ladder it will look something like this:

Stop Start Motor
|----| |--+-----| |-----+------( )---|
| |
| Motor |
+-----| |-----+



This is a basic drawing for a reversing motor using older standards in the US, the proper method now is to have the OL(overloads) on the supply side.:
reversingmotor.gif

Another simple version can be seen here:
http://www.patchn.com/electrical.htm
It that picture where L1 and L2 feed the control circuit there should be a transformer or DC power supply similar to the picture above. The transformer is above the Stop button its the 2 flat lines with the half circle lines over and above them. A transformer is shown here: http://www.patchn.com/symbols.htm

You could ask about symbols, they should be familiar with those:
http://www.patchn.com/electrical.htm
 
Last edited:
I couldn't imagine interviewing someone in a specialty that I didn't know a good bit about. Even if you had a list of questions and answers, there are many times more than a few correct answers to a question.

I would equate this situation to myself interviewing a canditate for a medical doctor's position in a hospital. "The leg bone is connected to what?"
 
Mr. B might be the HR type who's been tasked with finding an electrician who has some PLC experience. After passing muster with Mr. B, the applicant is then sent on to the electrical maintenance group for further vetting.

Geeze! This board is getting more and more obstinate by the day!

Remind me never to ask a question in here that I don't already know the answer to... otherwise, I'd probably get a bunch of smarmy answers from a bunch of self-important boors.
 
If Don is correct as to the office of Mr. B then Mr. B should have asked his electrical maintenance group for a proper set of pre-qualifying questions, possibly in a multiple choice or true/false form so there would be no electrical judgement needed on Mr. B's part.
 
Bernie,

And if the electrical group had been asked that question, four weeks ago, with three reminders sent, and the interview tomorrow, and still no answer... What should Mr. B have done? Maybe an internet search on PLC + electrician, and ask the "experts" who like answering questions to feed their egos.

Or maybe he'll get answered by those whose egos are fed by belittling others.

My point was that it is plausible that this was a legitimate question, asked in earnest.

I'm not saying this IS what happened, but that it COULD BE what happened. I know I don't always get answers to my emails, and I have to go somewhere else for answers (or just "wing it" the best I can).
 
You may be right in your observations. In an early job interview I was handed a list of minimum qualifications by the interviewer (who obviously hadn't the faintest idea of the meaning of them) and asked "Can you do this?". I replied "yes" and easily went on to the next level. (And as a matter of fact I could, well most of them at least.)
 
Mr. B might be the HR type who's been tasked with finding an electrician who has some PLC experience. After passing muster with Mr. B, the applicant is then sent on to the electrical maintenance group for further vetting.

If that is what his plans are with these questions, then Casey gave him a decent set of questions and he is good to go. I didn't read that in his question.

My point was that having a list of questions and answers may him no good if the answers are not evaluated by someone who understands the subject. He may accept someone that doesn't really know what they are doing and he may pass up someone that was very good.

If (making a broad assumption like you did Don) the HR guy was thinking he could tackle the interview with a simple list of Q & A on his own, our comments may have enlightned him to the complexity of the task he was contemplating and he may appreciate it.

I don't see any 'belittlement' in this thread.
 
SimonGoldsworthy said:
If you need to ask for questions then you shouldn't be conducting the interview.

If u need 2 go "Off Topic" then u should do it in u're own posts.

rsdoran said:
If the position is not for a full time programmer but more for electrician with plc skills then worry about the electrical part the most.

U r right, but we seem to get good Electricians with no PLC knowledge and they do need a little.

DonsDaMan said:
Remind me never to ask a question in here that I don't already know the answer to.
Ya, me 2...

kc9ih said:
Possibly. Take a look at his 20 posts.....

20 posts cause of replies like the above.(y)

To those that helped, thanx alot. And to those that didn't, thanx for waisting u're time discussing who and wot I am. :p

I'm an Electrician that learned PLC's myself by stealing with my eyes. I hav done alot of programming. Mostly analog, PID controlling etc.
My problem is that I'm not good with the terminology and don't want to use the wrong words in conducting the interview looking stupid hence this post.

I just needed a place to start from.

TX KC... ****...there are sum questions I don even know the answers to. Maybe ask them in another post... hmmm, but then again, wud prolly get replies like "GOOGLE IT!!!" from the likes of mr Simon and his crew :angr:
 

Similar Topics

Will be doing some interviews for the next couple weeks as we need to add a couple more E&I technicians with lite PLC programming and heavy...
Replies
14
Views
6,644
i have an interview for which i was preparing for a week..but i am worrying if he ask some thing else. can experianced engineers and managers...
Replies
0
Views
2,901
Re: Interview questions Hello everyone. I am familiar with SLC and Wonderware. There is these interview questions please see below. What are the...
Replies
2
Views
3,023
I have been asked to prepare questionaire for interviewing new applicants for an electrician job. I would like your help in determining...
Replies
36
Views
35,495
This is maybe off topic, but I just had an interview at Amazon and was asked to do this question. I was blanked in the head, was wondering if...
Replies
14
Views
3,792
Back
Top Bottom