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  • Author Author: dubbie
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TempMeter#2 : Improved Accuracy by Using a Laser Poiter

dubbie

Proving Science

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Although my original Tempmeter (TempMeter : Measuring Temperature with a Brass Rod  ) does successfully measure temperature it requires quite a large temperature change to create a visible alteration to the indicator. It was suggested that by Dave Ingles and John Wiltrout that a mirror could be used with a laser to increase  the sensitivity, so I thought I would try it out.

 

I 3D printed a small holder for some circular mirror pieces that I happened to have, putting two identical mirrors either side of the 1 mm rod used to make the pointer turn. See below. I used two mirrors to balance the unit and avoid any turning torgue problems.

 

 

It is essentially just a small washer shape with an indent each side to hold the mirrors and a 1 mm hole through the side.

 

I used a small laser pointer (it's a cat's toy!) Bluetac'ed onto the side of the piece of reconstituted marble stone and adjusted to shine onto the centre of the small mirrors. The complete working system is shown below in the video.

 

 

After trying the ceiling as the display I thought I would try using a wall instead to see if the movement was more visible and it was.

 

 

I also noticed that the laser dot seemed to be sensitive to vibration as well. It seemed to me that if I tapped the stone base that the laser dot did jiggle slightly. It might have just been my eyes but it would make sense that if you make the system sensitive enough then it will measure vibration. Maybe it could be a combined temperature and vibration measuring meter!

 

Dubbie

Anonymous
  • in reply to beacon_dave

    Dave,

     

    I used to buy a fair bit of stuff from Maplin, for work, as they would sometimes do worthwhile discounts of their robot toys which I would then buy in bulk for use in laboratories. I had solar panels, drones, robot arms, all sorts of stuff.

     

    Dubbie

  • Very cool solution to sensing the rod rotation. Well done!

  • in reply to dubbie

    I remember Maplin Electronics doing one as a kit in the 80's - a helium neon laser tube with two motors mounted at the output with a couple of 45 degree mirrors on their shafts. Ah-ha... and here it is...

     

    https://worldradiohistory.com/UK/Mapelin/Maplin-Project-Book-29.pdf#page=19

     

    Just another idea but you could perhaps use a lever type linkage on the end of the metal rod with a mirror on the other end of the linkage. There will likely be significant force available through the expansion of the metal rod to be able to push/pull a short arm of a lever and have the mirror attached to the longer arm, amplifying the movement even more.

  • in reply to jw0752

    John,

     

    I originally displayed on the ceiling with the hope of getting that increased sensitivity effect, but it was really hard to hold the camera in one hand, heat the brass rod and keep everything stable. It was much easier to see on the wall. I did think about extending the length of the brass rod by soldering two of them together, in order to increase the movement, but it does not seem necessary with this much longer pointer.

     

    Dubbie

  • in reply to beacon_dave

    Dave,

     

    I have toyed with the idea of making a vector laser projector thingy for several years, but never actually got around to doing anything about it. Now that I have made a single dimension mirror deflector the possibilities become more realisable.

     

    I never thought about using a front surfaced mirror and I don't have one anyway. The circular mirrors I used are from card when I bought a packet of them many years ago for making cards. I had forgotten that I had them until I started looking for a mirror. I guess there must be some diffraction effect due to the glass but I did not notice anything. Maybe I will have to have a closer look.

     

    Dubbie