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Which sensor is suitable for these jobs ?? — Parallax Forums

Which sensor is suitable for these jobs ??

arbjarbj Posts: 3
edited 2010-07-17 14:49 in Accessories
Hi,

I have the following queries....

1. Can the Ping ultrasonic sensor be used to detect water level in a tank ??
2. Which sensor is suitable for measuring thickness of a sheet of rubber, resolution of 1 to 1.5 mm is acceptable .

thanks
arb

Comments

  • underworldmanunderworldman Posts: 22
    edited 2010-07-16 11:01
    I can only answer the first question, and the answer is YES. It can! BUT you have to ensure that you cancel the effect of humidity if it was to be used in this situation over a long period of time, and once you do this, you can use it for a very long time without damaging the sensor. Keep in mind that parallax has done some tests on the water level measurements with the PING))) sensor and to me, the only challenge there was the humidity. There are ways around this, and no way is 100% efficient, so there will be very small amounts of humidity around, but is as close as you can get.

    I would be one of the most happiest persons if parallax actually came up with a water proof PING sensor. And this is no tall order because if non-water resistant sensors can be made, then why not waterproof? Also, I'm sure many people have asked them time and again or even requested them to come up with one.

    Post Edited (underworldman) : 7/16/2010 11:09:23 AM GMT
  • arbjarbj Posts: 3
    edited 2010-07-16 12:13
    I am trying to make a water level detector for the water tank in my house, this is situated quite high up and I thought the Ping sensor would do the job.

    So if the sensor is enclosed inside a metal or a plastic box, will this prevent humidity from affecting the sensor ?.
  • LeonLeon Posts: 7,620
    edited 2010-07-16 14:41
    A pressure sensor at the bottom of the tank is often used for that sort of application, the water depth can easily be calculated. Freescale makes suitable sensors, and has an app note on the technique:

    www.freescale.com/webapp/sps/site/overview.jsp?code=DRSNSPRSSR

    Weighing the tank with a load cell is another option, but will probably be more expensive.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Leon Heller
    Amateur radio callsign: G1HSM

    Post Edited (Leon) : 7/16/2010 3:07:11 PM GMT
  • Mike GreenMike Green Posts: 23,101
    edited 2010-07-16 15:07
    Parallax does now have a water-resistant PING sensor. Check their webstore
  • ElectricAyeElectricAye Posts: 4,561
    edited 2010-07-16 16:11
    arbj said...
    ....
    2. Which sensor is suitable for measuring thickness of a sheet of rubber, resolution of 1 to 1.5 mm is acceptable .....

    A lot depends on whether you are wanting to measuring the thickness by sensing it from one side of the rubber or if you might be able to have a sensor system that is located on both sides. I have no experience with this, so this is just a guess: but if the rubber is somewhat translucent and fairly homogeneous, perhaps you could shine an LED through it and have something like the TSL230 sensor observe changes in light transmission.

    www.parallax.com/tabid/768/txtSearch/TSL230/List/0/SortField/4/Default.aspx

    If you can measure the rubber only from a single side, perhaps you can still use the TSL230 by having an LED shine into the rubber, perhaps aiming at a reflector on the opposite side, and then have the TSL230 measure the light scattering backwards, but this is probably not as good as a system that shines light straight through the material.

    For the thickness you're talking about, I'm guessing a red LED or IR emitter LED would have the best chance of success since the longer wavelengths of light tend to penetrate deeper through materials.

    But again, this is for a rubber that is at least somewhat translucent.


    Just a thought.
  • LeonLeon Posts: 7,620
    edited 2010-07-16 16:36
    I think that thin sheets of stuff are often measured with beta emission from a suitable source. That's most suitable for a manufacturing process, of course.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Leon Heller
    Amateur radio callsign: G1HSM
  • Larry~Larry~ Posts: 242
    edited 2010-07-16 16:51
    this is just an example of thickness measurement these units come with rs232 output, I think you may need something with a roller? but with this idea you can search the web


    http://www.labtek.net/peacock-11.htm
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-07-16 17:08
    If the rubber sheet is lying on a flat surface, you can measure its thickness by determining the height of the top surface. The geometry presented in this thread may do the trick for you. Very fine measurements can be obtained by either 1) having the imager very close to the subject, 2) using a longer focal-length lens, and/or 3) making the incident angle of the laser highly oblique.

    -Phil
  • hover1hover1 Posts: 1,929
    edited 2010-07-16 17:25
    Mike,
    I think the new PING is on hold.

    http://forums.parallax.com/forums/default.aspx?f=5&m=354639

    Can't find it on the Parallax website.

    Jim
    Mike Green said...
    Parallax does now have a water-resistant PING sensor. Check their webstore
  • hover1hover1 Posts: 1,929
    edited 2010-07-16 17:28
    If you were to encase the PING in a box, it would not be able to "see". It would be taking reflections off the inside of the box.

    Parallax DID have a water resistant product in line, but they have had some problems.

    http://forums.parallax.com/forums/default.aspx?f=5&m=354639

    Jim
    arbj said...
    I am trying to make a water level detector for the water tank in my house, this is situated quite high up and I thought the Ping sensor would do the job.

    So if the sensor is enclosed inside a metal or a plastic box, will this prevent humidity from affecting the sensor ?.
  • ElectricAyeElectricAye Posts: 4,561
    edited 2010-07-16 18:06
    Phil Pilgrim (PhiPi) said...
    If the rubber sheet is lying on a flat surface, you can measure its thickness by determining the height of the top surface....

    arb,

    keep in mind that if your rubber is moving along on top of or between some kind of roller system, the rubber will be under tension and the tension forces need to be held constant so you aren't randomly stretching the rubber and getting random results.
  • ElectricAyeElectricAye Posts: 4,561
    edited 2010-07-17 01:13
    blush.gif
    Oops. I just noticed that your resolution is 1 to 1.5 mm. My first responses were based on thinking that was your range. How thick is this rubber on average?
  • arbjarbj Posts: 3
    edited 2010-07-17 05:14
    thanks all for the replies.

    the rubber is not translucent..

    the thickness of the rubber sheet is around 8-10 mm but this can be more in some cases,

    The pressure sensor looks good, but I think it may be expensive for a home project.

    The laser idea looks ideal I have seen these being used in tyre industries.
  • Ed TEd T Posts: 50
    edited 2010-07-17 14:49
    I talked with Ken at UPEW and they are not currently selling a waterproof PING due to some performance issues. I don't think they are actively working on this right now.

    - Ed

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