Control Questions

[Clay B.]

Would a competent controls engineer be competent enough to be a member here and be following this thread?

Not sure. I am follwing this thread but I would question my competency most days. I am not sure exactly what we have set up with the head hunter but if someone following this thread is intrested please send me an message and I will see what I can do.

Obviously spelling and using sequential numbers is not a high priority but being able to program PLC's and HMI's is.
Job is located in Monroe NC.

 

[Steve Bailey]

This is just my opinion, but the ability to answer "Industrial Controls for $200, Alex" type questions doesn't strike me as the best way to weed out unqualified candidates. I fear that you'll eliminate too many good candidates with the questions you've asked, especially since the headhunter is only going to be able to see the responses in black and white.

Question #1: I'm sure there are lots of people who have been building panels that come pretty close to complying with NFPA 79 without being able to name the standard. To them the standard is "commonly accepted best practice". Suppose somebody answers "UL508"?

Question #2, do you really want to eliminate someone who answered "Modbus RTU" instead of ASCII?

Question #3; Not all HMI packages use the term "tag". The term itself comes from the process industry. A person with experience in discrete parts manufacturing might not be as familiar with it. Of course, if you're in the process industry, you may only want candidates with that background. If that's the case, then it's as good a screening question as any. Suppose a candidate described lockout/tagout procedures in response to the question?

Question #4 is mostly trivia, along the same lines as the unitary, modular, rack-mount question on the British HNC exam. If a person doesn't know the answers you're looking for, does that mean he/she can't program a PLC or layout a control panel?

 

[mellis]

I think your questions are probably weeding out too many applicants. I think the reponses here bear that out.

Personally, I'd have to look up #1 and unless you refer to it a lot, I doubt many would have that number at their fingertips. Now if they didn't know what NFPA stands for...

For #2 ASCII stands for American Standard Code for Information Interchange. It's not really a serial protocol, at least there is room for confusion. Modbus or DF1 are protocols. All I can suggest here is to make the question more specific. Pick a plc processor and ask a question that someone familiar with that processor would recognize.

The tag question is ok, but a more focused question will get a more focused answer. Since a headhunter is going to be asking these questions and won't be able to clarify, a more detailed question will get you better data.

No doubt that 8 bits = 1 byte. 16 bits usually = 1 word but it's a bit ambiguous. There are more than one type of floating point representation. Give the IEEE number and you lock it down. Most common is 32 bits of course. Of the 4 questions, I think this is your most effective "weeding" one.

Basically, keep in mind that the person asking these questions will not be able to answer any questions about them or clarify them in any way. So make questions that don't require any clarification.

 

[Brian123]

My answer to number 2 would have been Modbus. When you say ASCII, do you mean Modbus ASCII? There are other forms of Modbus too (RTU and TCP).

Brian

 

[jimbo3123]

I know this has been said, but your answer to question #2 is flat-out wrong. ASCII is not a protocol. It is a standard code of digital representations of characters. See here: http://en.wikipedia.org/wiki/ASCII.

The rest of the questions are just ambiguous or trivia of questionable use. That's just my opinion though.

 

[Clay B.]

First thanks for the responce

Personally, I'd have to look up #1 and unless you refer to it a lot, I doubt many would have that number at their fingertips. Now if they didn't know what NFPA stands for...

Yes I thought about that, but I kind of feel that if you do not know that NFPA 79 is then I would expect that you have not done much on the design side.

For #2 ASCII stands for American Standard Code for Information Interchange. It's not really a serial protocol, at least there is room for confusion. Modbus or DF1 are protocols. All I can suggest here is to make the question more specific. Pick a plc processor and ask a question that someone familiar with that processor would recognize

.

Well I think it is a protocol in the same sense as Modbus or DF1. I mean if you think about it, do you not set each up the same way. If your looking for modbus, DF1 or ASCII on a given port don't you have to set the port up for that kind of data?

The tag question is ok, but a more focused question will get a more focused answer. Since a headhunter is going to be asking these questions and won't be able to clarify, a more detailed question will get you better data.

True, I based my questions on what I know and tags are something I always associate to HMI's infact I do not know of an HMI platform that does not use tags or call them out as tags. How would you make this a more detailed question?

No doubt that 8 bits = 1 byte. 16 bits usually = 1 word but it's a bit ambiguous. There are more than one type of floating point representation. Give the IEEE number and you lock it down. Most common is 32 bits of course. Of the 4 questions, I think this is your most effective "weeding" one.

Well I guess this shows my sheltered life. I have never seen a float be anything other than 32 bits. Might be best to say " In a Siemens or Allen Bradly PLC how many bits is a float?"

 

[harryting]

Well, a "word" can be any different of number bits, for one. (correct me if I'm wrong)

Anyhow, as it has been said above a few times. I agree with the "trivia" description.

FWIW, I look for the type of person and not what the person knows already. Training a good person is easy, deal with a know-it-all but a PIA is impossible.

 

[Paullys50]

I'll agree with the others that these questions are very poor given the purpose. No doubt many great applicants would be missed. Of course it all depends on what you are expecting from the head hunter. If you want someone who knows the NFPA79 standard like the back of their hand...then #1 is legitimate. But if you are just looking to make sure you get applicants who are actually in the industry then it's not appropriate.

Some generic questions that I can think of:

1 - What is a PLC? If they say "Programmable Logic Controller" somewhere in the answer then they get a gold star.

2 - What is an HMI? If they say "Human Machine Interface" somewhere in the answer then they get a gold star.

3 - What PLC/PAC platform(s) have you used? If they say "Allen Bradley", or "GE Fanuc", or "Siemens"...then they get a gold star.

4 - What type of PLC networks have you used? If they say "RIO" or "Ethernet" or "ControlNet" or "Profibus"...then they get a gold star.

Get 3 of 4 gold stars, send the resume to me for further review.

You could also ask:

5 - What are your salary requirements?

6 - Are you willing to travel?

7 - Are you willing to re-locate?

All depends on the candidates you want to spend your valuable time on.

Personally "trivial" questions in any interview make me uncomfortable as I don't believe they can paint a clear picture especially if I'm looking to develop someone. I need people who can learn, who can think on their toes, and who fit with the team.

 

[tomalbright]

Don't be "over specific", either. During my off-time, I had a call froma recruiter wondering if I had any RSViewSE experience. I have a lot of -32 and -ME experience, and I told her that. And, that basically, the programs were pretty much the same. But no, without the SE experience, I was a no-go, no-talk-to candidate.

Amazing what 25 years of experience will do for you in the face of someone who can't walk and chew gum at the same time. And makes decisions like that one.

 

[Clay B.]

Don't be "over specific", either. During my off-time, I had a call froma recruiter wondering if I had any RSViewSE experience. I have a lot of -32 and -ME experience, and I told her that. And, that basically, the programs were pretty much the same. But no, without the SE experience, I was a no-go, no-talk-to candidate.

Amazing what 25 years of experience will do for you in the face of someone who can't walk and chew gum at the same time. And makes decisions like that one.

This is exactly my problem. We do not have a HR department hence the use of a recruiter. I know a recruiter has no clue what I do so I came up with these questions. From the feedback I have my questions pretty much suck so I have started a new thread asking suggestions.

 

[tomalbright]

I had several interviews where I was asked simply "if I could perform the job". My resume listed my experiences, and a brief interview was conducted where I was asked some basic questions, like:

"Have you maintained PLC equipment?"

"Have you built an application from scratch?"

...etc. If you are looking for a controls man - not engineer - you will have a good paper record of where he has been. What you fail to see is how good he is. Lots of jobs? A few jobs? Answers every question like he's superman? There's no good way to tell. A 25 year old guy won't have the experience of a 50 year old guy. However, the 50 year old guy might be looking for an "easy out" job, and probably won't be a road warrior. You might have to take youth over experience.

Might as well flip a coin. We hired some guys on my last job that were either totally useless or crackheads. You sure couldn't tell by the resume. We're talking "umpteen years of PLC experience" but who knows?

A straightforward approach means you'll do more interviews, but will get a good sense of what somebody says they can do. You have to ask the right questions, but assume a PLC guy knows PLCs.

"Can you do the job?" after showing him the plant may be your best approach. Watch out for superman.

 

[Plastic]

Your questions - reworded (alt)

Our Company has decided to hire another Controls Engineer. My boss asked me to come up with 4 questions that a head hunter could ask perspective applicants. I listed the questions below. I think they are pretty good but according to the head hunter the first 5 applicants could not answer the questions. Could you guys take a look at them and see what you think of the questions.

1) What is the NFPA standard that applies to industrial pael Construction?

2)What is the nonproprietary standard protocal used to transfer in a serial (RS232 and RSA485) network?

3)What is a tag and how is it used?

5)How many bits in a byte,word and float?

I personally think those are simple questions but I am asking questions I already know the answer to.

Here are some alternate questions:
1. What does the acronym NFPA represent?
1a. What is NFPA70?
1b. What is NFPA70e?
1c. What is NFPA79?
1d. What is the difference between a CODE, and a Standard?

2. What does 9600,N,8,1 mean?

3a. Do PLC's use TAGs or Addresses?
3b. Do PAC's use TAGs or Addresses?
3c. What is PLC?
3d. What is PAC?

4. ? there was no 4 in your original post?

5a. How many bits in a SINT
5b. How many bits in a INT
5c. How many bits in a DINT

I would then review the responses given by the prospective employee. If they miss a question or two, I would not condemn them, but I would read the text of thier response to see if they can, "walk-the-walk".

 

[TimWilborne]

I'm with Ron, #4 is the only one I got right. The problem I see is that you are having a recruiter ask the question so if the applicant's answers don't match the answer's you provided the recruiter, they will be weeded out even though their answers may be different than yours.

My answers would be
1. 79 on a good day, if I've been doing a lot with workplace safety I might throw 70E out by accident.

2. I would say Modbus, but I could see why you would say ASCII too. Guess I'm out of the running

3. Controllogix based tags actually came to mind first, if the recruiter would let me use the shotgun answer I might be about to come up with HMI

4. Yes I can show up for work sober

5. This would probably show hands on experience. I haven't met many people straight out of school that actually understand this. They get it right on the test, but they don't get a firm grasp on it until you use it some. I still have to look up floating to remember which bit holds what when manipulating data in a device that doesn't support floating

 

[KP_EENG]

Obviously spelling and using sequential numbers is not a high priority but being able to program PLC's and HMI's is.
Job is located in Monroe NC.

Have you checked with the Alumni Associations or student placement offices at CPCC or UNCC? I am a graduate of both schools and I think that they do a pretty good job assisting graduates with job searches.

Regards