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What are an engineer's most common concerns when selecting instrumentation?

  1. Mar 27, 2017 #1
    Hi everyone, I'm Jacob Cheng from China, working in an electronic instrument manufacturer, and this is not a promotion content, I'm here asking for help.
    As a freshman of marketing promotion in the electronic instrument, I have no idea about what topic will engineers interested in. So, I'm here today to ask for a little favor from an expert like you guys, sincerely.
    We manufacturing digital DC power supply, frequency converter, all kind of power testing equipment the most. For example, the frequency converter, use to simulate power network for product testing. Then you wanna know about this machine, what you want to ask? Here is some of my thinking:
    • What's the feature of this machine? (compare with general model)
    • Compare with XXX brand, what' the result?
    • What's the power core? What's the capability between different core?
    • What material made of? That decided how long I could use it.
    Anything else comes up?
    I know I maybe ask a stupid question, but I really need help, please leave your comment, thank you, guys.
    Last edited: Mar 27, 2017
  2. jcsd
  3. Mar 27, 2017 #2


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    1. The specifications need to be useful, meaningful and accurate. Each type of product will require a different set of specifications. Engineers need to make wise professional decisions based on appropriate specifications. The product will not sell if it does not have appropriate specifications.

    2. Materials and quality of manufacture need to be selected for durability. When an engineer specifies the product, the engineer must be certain that the product will perform as the seller says it will perform. Engineers do not buy disposable toys.

    3. Quality of design is important. There is no advantage in manufacturing a product that is unreliable in some situations. Specify the limits to operation.
  4. Mar 27, 2017 #3
    Sneak in to a company where your stuff (hoped to be) used.
    Ask the engineers, when there are no managers in sight.
    Then ask the technicians too (when there are no engineers and managers in sight).
  5. Mar 27, 2017 #4


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    In addition to the other replies, lately I've been very interested in the control and monitoring interfaces to the instruments. Can I interface to it via USB? Serial Port? GPIB? etc. And how easy is it to control with my software? Do you have a pre-packaged control interface like LeCroy's WaveStudio:


    If I want to write my own control programs in C#, for example, are your instruments supported by National Instruments Measurement Studio?

  6. Mar 28, 2017 #5
    Thank you for the kindly advice. So your point is engineer needs appropriate specifications and how good materials the machine used to know the machine will perform, and the reliable quality to enhance their confidence about our products, right?
  7. Mar 28, 2017 #6
    Thank you for the advice, it's really helpful, and got me inspire. Show people how easy this machine to control. Back to frequency converter, show the details of control dashboard when it's regular frequency converter. Show both control dashboard and monitoring interfaces, also supported software when it's programmable frequency converter, right? We got programable frequency converter ready to post, I will take your advice, thank you.
  8. Mar 28, 2017 #7


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    Cost. Anybody ever manage a budget?
  9. Mar 28, 2017 #8
    Sure cost must be a big thing that you consider with, but let's say under your budget, you got several choices, what will be your next thinking?
  10. Mar 28, 2017 #9


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    I agree with many of the several comments up thread, but I found it more than odd that cost was never mentioned in half a dozen posts. Instrumentation cost varies greatly, so cost or budget is typically the first parameter which then down selects the remaining parameters. When I have ample budget, cost is *still* a major factor, as access to several different types of instrumentation typically remains far more useful than the one piece of gear with far more precision and features than required to get the job done.
    Last edited: Mar 28, 2017
  11. Mar 28, 2017 #10

    jim hardy

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    Interface protocol is a great suggestion.

    Since i have no idea what your machine does
    but i have spent a lot of time studying inrush current characteristics of instrumentation loads in the power plant
    and studying overload characteristics of power supplies, DC to AC inverters , fuses ,circuit breakers and the like
    it seems natural to me somebody might use your machine for such testing to assure he is about to build a "well co-ordinated*" instrument power system.
    *(Co-ordination has a specific meaning , see
    http://www.tnbpowersolutions.com/sites/default/files/webfm/resources/upload/Cyberex Data Center/ABB Breakers and Panelboards/Breaker Coordination WP.pdf )

    I'd want to know how your machine behaves with overloads particularly brief ones like one-half to five cycles duration.
    How much current into a dead short ? Voltage droop ?

    A wall outlet fed from a typical lighting transformer behaves quite differently than one fed from a typical thyristor inverter.
  12. Mar 28, 2017 #11
    I agree with you, shows interface protocol is a great idea. It seems you guys love programmable power supply to do great things.
    Cloud you please tell me more about "one-half to five cycles duration"? How to do, and is there any similar testing, I can take a video to show how the machine behaves.
  13. Mar 29, 2017 #12

    jim hardy

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    You said this device simulates the power network
    not knowing what type of product you had in mind i just guessed you're using this thing to provide AC power of varying amplitude and frequency for testing some kind of electronic products.

    In the testing i did so many years ago i examined the starting current of many of the plant's instruments , then examined the behavior of our instrument power inverters when subjected to those starting loads.

    Electronic supplies drew a large first half cycle current maybe 5X normal , sometimes the second peak was also a large one too but after that current returns to normal. That's an overcurrent transient of one-half to one cycle duration.
    It was important that voltage from our source, which was inverters, not droop during that brief overload else it'd upset other instruments on the same bus.
    Relays drew maybe 10X for a cycle as their plunger moves in.
    Electric motors inside instruments like recorders are small so draw less severe overcurrent but for longer time, twenty cycles was not unusual.
    One system had a lot of transformer loads. Transformers are sensitive to what point in the line cycle you apply voltage. I measured hundred amp peaks (some 30X normal) when switched on right at zero crossing. That was a severe transient of two cycles duration.

    Next i tested scores of fuses and circuit breakers to find devices that would protect against genuine short circuits but would not mis-operate from normal startup transients.

    Since our inverters' voltage drooped noticeably on overloads i had to use one of them as source for this testing. A device like yours would have been nice because i could program it to mimic the overload behavior of my inverters and do that testing in a lab instead of out in the real plant.

    I used a dual trace 'scope. Mind you this was 1974 and i didn't have a digital storage scope, in those days we used a Polaroid camera to capture a single trace..
    Current on one trace and voltage on the other , sweep speed set so the transient fills about 2/3 of the screen.
    You'd tell people it is suitable for testing co-ordination of overcurrent protective devices to a weak source such as an inverter or ferroresonant transformer..

    Ability to set its droop or sag would be a plus If that's something it can do. . Here's shape of a typical ferroresonant inverter's droop
    as you see it's not linear like a transformer. I call it "Flimsy" or "Weak" compared to the stout transformer behind a wall socket.

    old jim
    Last edited: Mar 29, 2017
  14. Mar 29, 2017 #13
    Thanks Old Jim for posting so mush info, but it a bit hard for me to digest that, I will share this with our engineer, thanks again.
  15. Mar 30, 2017 #14
    Engineers will inspect
    they can take whatever it is apart
    An old friend of mine her dad is an electrical engineer he would purchase something from a company and if he did not see what he was sold back it went
  16. Mar 30, 2017 #15
    Do you mean describe accurately, it is what it is?
  17. Mar 31, 2017 #16
    I am talking about advertising claims
    Like the" best ever" or "new and improved" and try to avoid saying "state of the art" unless it really is
  18. Mar 31, 2017 #17
    We don't like that way either, always do objective description, well, do the best.
  19. Mar 31, 2017 #18
    Your probably going do to ok then
    good luck
  20. Apr 3, 2017 #19
    Someone already mentioned good specifications, but it is also important that the devices meet those specifications.
    I have used some devices, that on a good day might meet their specs,
    but like the old HP equipment, it would always meet or likely exceed the specifications.
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