Connect with us

Moving 4 x trimmers...

Discussion in 'General Electronics Discussion' started by bowlingo, May 12, 2013.

Scroll to continue with content
  1. bowlingo

    bowlingo

    40
    0
    Jun 29, 2011
    Hello all,

    I have one of these

    http://www.omega.co.uk/ppt/pptsc.asp?ref=CDTX300

    This is within a big adaptable box and I need to move the 4 x trimmers so the user can insert a small screwdriver into the side of the big adaptable box and turn them

    I have taken the unit apart (see below pics)

    [​IMG]

    [​IMG]

    [​IMG]

    The length I need to extend these is around 300mm

    According to the spec sheet

    http://www.bourns.com/pdfs/3296.pdf

    one is 200 ohms

    and the other three are 50K ohms

    Due to these working on resistance if I were to get 4 x 300mm lengths of 3 core screened cable, desolder them and move them do you think it is possible? In theory they are easy to mount on the inside of the big adaptable box as all I would need to do is drill 4 x holes into it and possibly glue them in place so the user just pushes in a screwdriver and turns them.......
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    11,160
    2,548
    Nov 17, 2011
    From a theoretical point of view it is possible to desolder the trimmers and attach them by a length of wire. However, these trimmers are probably in a sensitive part of the circuit. Any length of wire will act as an antenna and couple noise into the circuit. You can give it a try and see, what happens. Using shielded wire (shield to circuit ground) may help.

    On the other hand: trimmers are not meant to be operated regularly. They will possibly wear out rahter quickly if used as potentiometers. If the user has to access the trimmers only rather seldom, You can drill a hole in each of the respective positions of the trimmers and have the user insert a small screwdriver for adjustment. Placing some kind of guide along the path for the screwdriver will help the user fnd the screw atop the trimmer. You could e.g.glue a small plastic tube to the holes such that the other end of the tube ends right on top of the trimmer's screw.
     
  3. davenn

    davenn Moderator

    13,786
    1,936
    Sep 5, 2009
    Yeah I am wondering why you would want to be adjusting them on a regular basis.??

    the unit should be calibrated with them and set and probably only adjusted again 12 months later during another calibration check.

    If you are adjusting them all the time, the unit is NEVER going to be calibrated and the readings you take are going to be totally meaningless!!

    Dave
     
  4. bowlingo

    bowlingo

    40
    0
    Jun 29, 2011
    The probes are in use 24/7...If the values drift slightly upon checking every couple of months then they may need recalibrating...usually the probes get a build up of salts etc and any drifts can be resolved by cleaning them...also ph probes have a quite low shelf life.

    The reason I would like to be able to get the calibration pots and some other items into the outside of the box is top stop the user having to open the main box up and go poking around with screwdrivers..if I can move these pots and the other bits then the only reason someone would need to open the box would be to replace the back up battery every couple of years......
     
    Last edited: May 12, 2013
  5. davenn

    davenn Moderator

    13,786
    1,936
    Sep 5, 2009

    And being readily accessable on the outside will have everyone messing around with them constantly .... face it people love to twiddle knobs etc ... and the unit is never going to be in calibration
    having worked in various labs, and knowing human psychology, you are opening the unit to mis use ;)

    extending them out with some short lengths of wire is no problem

    good luck

    Dave
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-