Group Actions
Engagement
  • Author Author: jw0752
  • Date Created: Date Created
  • Views 1009 views
  • Likes 10 likes
  • Comments 9 comments
Related
Recommended

Sticky Analog Voltmeter

jw0752

I happened to notice the other day that an analog voltmeter that I built a couple years ago was reading 10 volts. Now this alone would not have been of any concern except for the fact that the power supply was not turned on nor had it been turned on for several days. I went over and tapped the meter and it dutifully dropped back to zero. Years ago when I did service work for Radio Shack it was common to have the little analog multimeters come in for repair with stuck meter movements. I would take them apart and the usual cause would be a metal filing suspended in the magnetic field where the movement coil would normally swing. Once the filing was spotted any sharply pointed ferromagnetic tool could extract the filing by touching it with the point of the tool and pulling it out using the magnetic field. Since the meter movement of this power supply was not very expensive I expected to find a similar problem. I really like this power supply and I really didn't want to have to replace the meter so I popped the front cover off. To my delight this is what I found:

 

image

 

There just south east of the DH-670 was a hair like finger of white paint acting like a tiny ratchet. The needle could pass by it on the way up but on the way down it would get hung up. The picture also revealed a couple other signs of the quality of this meter. Note the rust on the screws holding the front plate and even a dust bunny clinging to the left mounting screw pulled perhaps from the sleeve of the factory assembler. Fortunately when I removed the finger of paint and the dust bunny the meter started working as good a new and since I have tolerant standards in my test equipment more than adequate for me.

 

John

  • in reply to beacon_dave

    There are a number of 'tents' around, and I see the Manfrotto has the infinity stlye background incororated into it.

     

    I've looked at them, but never really liked them.

    I find they produce rather flat lighting if you're not really careful.

     

    The reflections can also be a challenge, since you now have 180 deg light hitting the object.

     

    I saw a cheap version used the other day with a box and some polystyrene, which meant it could be picked up and put to one side easily.

    The light was inside so it was easy to arrange the object and camera position to suit.

     

    In image the light source is above and to the right, which gives shadowing to the object, which we naturally see everyday.

     

     

    John you could add a sheet of black paper to the rear or use white card to give similar results.

    For bigger objects bouncing the source off the roof will help spread it, but if the roof is coloured, then you're in trouble.

     

     

    Mark

  • in reply to jw0752

    Hi John,

     

    You can make a light tent using just about any white translucent cloth to act as a diffuser to produce soft light which wraps around the subject. This blow lamp was done with an upturned chair with a white bed sheet thrown over the chair legs

    image

     

    Using paper or aluminium foil as a 'bounce' reflector will help as well.

     

    Dave

  • in reply to beacon_dave

    Hi Dave,

     

    Excellent idea. I will look into getting one but in the meantime I can use Mark's paper idea too.

     

    John

  • in reply to jw0752

    John Wiltrout wrote:

     

    ... My biggest problem is usually arranging the lighting so I am not casting a shadow on what I want to take a picture of.

     

    You should find that a 'light tent' will help you out here. Something along the lines of this:

    https://www.manfrotto.co.uk/ephotomaker-small-kit-with-ezybalance

  • in reply to jw0752

    she got me a slightly upscale camera

    Well done that woman. image

     

    Having control over the aperature means you can get what you want in focus, and sometimes that means a lot of light, or very slow speeds.

    I've done some at 45 secs or more, just to ensure everything I wanted is in focus, and that was with good light coming in the window.

     

    Two suggestions for you John (and others) is a laminated piece of A4 paper to reflect light back into the object, you'll be amazed at the difference it can make sometimes.

    The advantage is you can curve it to focus what light you have.

    The other is don't be afraid to use the timer function on the camera if you don't have a remote trigger. It will stop you from shaking it.

     

     

    Mark