Remote Temperature Sensing of Moving Device

Discussion in 'The Projects Forum' started by jphizzle, Jan 5, 2016.

  1. jphizzle

    Thread Starter New Member

    Jan 5, 2016
    1
    0
    OK. I need help or essentially answers that I'm hoping to find here.

    I am designing a sensor system for a rotating machine wherein I want to measure the temperature at various points of the rotating portion of the machine. This would mean that I would need the sensors, the transducer and corresponding interfacing amplification circuit for the sensors, the multiplexer and the transmitter to move along with the rotating machine. And on the receiver side, I desire to have a receiver circuit connected to a computer for continuous data logging when the machine is running.

    From my studies, I've decided that I want to use:
    1. Thermocouple Type K sensors - Surface mountable ones with adhesive.
    Are Thermocouples reliable? Would you recommend I use any other temperature sensors. How would you suggest I hold them down? The portion that has to measured is honestly a flat surface of about 70mm by 16mm.
    Honestly, I was imagining a way to be able to embed the temperature sensors on a PCB so that all I would have to is just design the PCB cut out to the right dimensions and then place it on the flat surface from which the embedded sensors would be able to measure the temperature. The problem I understand in using this is that the temperature being measured would be a combination of both the PCB and the surface temperature. Any input here would be awesome!
    2. For the transducer, cold junction temperature compensation and the amplification of the signal, considering thermocouples, I understand I have a choice of AD597 or MAX81355. Does anyone know what is the difference between these two? I'm not able to determine which one I should use and what is the benefit or disadvantage of one over the other?
    I have understood that the terminal ends of the thermocouple cannot be soldered on to the PCB and would have to attached using screw terminals.
    3. Now, as I have multiple signals that need to be transmitted for the various points at which I am measuring the temperature, I understand I need to use a multiplexer. Am I correct? What type of multiplexer do I need to use?
    4. More importantly in choosing 2 & 3, how much does the consideration of the XBee wireless transmitter come into play in making the decision. See, the information I am getting for the transducer and the multiplexer are independent of the consideration of wireless data transmission. How does this factor into the selection of the right components for 2 & 3. Also, I noticed that this: (https://oceancontrols.com.au/KTA-259.html) exists which is a combination of what I need from 2 & 3. Understanding that every second all 8 signals are being transmitted every 0.125 seconds, would this be a good choice? How would I know that it is compatible with the XBee module I intend on using?

    I had this question as well. If I am connecting the sensor to the transducer and then to the XBee module, would I need a microcontroller present at the point of the multiplexer and the XBee slave to ensure that data is collected or is this something that can be programmed in the XBee slave before use. A key point in my construction is the lightness of the design so much so I was actually considering using a PAN1721 Bluetooth transmitter receiver but as you can see I'm not very well acquainted with much of this stuff and the more I read the more I have doubts and questions! Would you recommend a better wireless transmitter?

    I really hope people would be able to help me out here! I apologize if its too confusing and if theres anything you think I'm missing, please let me know and I will try to update it to be able to help you to help me!

    Also, if this is by any chance in the wrong sub please let me know!!! I really need help and this is my first time on here!
     
  2. Picbuster

    Member

    Dec 2, 2013
    374
    50
    More information on mechanical is needed. (size of rotating parts speed etc permanent measurement or occasionally ).
    At the first glance I would advice a infrared temp sensor very accurate, measure on distance and not to costly but useless in dirty environment.
    Wireless; use ant protocol ( each temp node has its own address, makes its own data path and makes it easy to present the values per sensor)
     
  3. sailorjoe

    Member

    Jun 4, 2013
    361
    63
    You want to mount multiple sensors on a flat plate that's only 70 mm by 16 mm, is that correct? Is the plate metal? How much temperature difference do you expect to see from one end to the other?
    How fast is the plate moving or rotating?
    How much accuracy do you need to measure?
    How many multiple sensors are you considering?
    How fast does the temperature on your flat plate rise and fall? Can your thermocouple keep up with it?

    You'll probably need that microcontroller to talk to the XBee device.

    Before this gets too complicated, have you considered just measuring one point with a thermocouple? If that works, then do the work for additional points, but if that doesn't work, then try something different. With thermal measurements in a dynamic environment, there are multiple thermal effects that need to be understood to make accurate measurements.
     
  4. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,531
    1,248
    What is the desired temperature range? Generally speaking, I've found thermistors to be much easier to use than thermocouples, but they have a narrower temp range.

    ak
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,524
    2,369
    You could also touch base with Omega Engineering dept, they can help in the selection, I have found thermocouples to be very accurate and more linear than thermistors.
    Max.
     
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