# Multimeter recomendations

Tony Duell ard at p850ug1.demon.co.uk
Tue Sep 21 14:36:10 CDT 2010

>
> Tony Duell wrote:
> > 1) You have ot dispmantle the meter to change the battery, and it's
> > assembeled with self-tapping screws going into the plastic case. I don't
> > know how many insertions they will stand.
>
> *if* you could fix yours, can you modify the case to make some form of hinged
> / clip-on battery compartment so that ceases to be an issue? It probably
> doesn't even have to be pretty, so long as it's functional.

Possibly. The problem with doing this (and the switch mod you suggested)
is that I do use my mutlmeter on live mains stuff from time to time (not
suprisingly). Now, there is obviously no isolation between the inputs and
hte battery, which means the battery is 'live' when I am testing mains,
etc. And any modifications would have to ensure that the there were no
exposed live parts.

>
> Personally, if I've got a tool or bit of equipment that I like, I'll do
> whatever I can to keep it going - and so long as it's not something rare, I
> don't mind making a few alterations to the original design to make it suit
> *my* needs better. I expect you can understand that!

Oh, indeed...

>
> Regarding the LCD, maybe it's a driver issue rather than the LCD itself? How
> do signals get from the PCB to the LCD - some form of ribbon cable, conductive
> rubber strips, or something else? Maybe dirt's got in there or something?

I wasnt clear in my fault description....

The LCD is not a dot-matrix one, it's a 7 segment thing with annunciators
and a row of bargraph segments at the bottom. When I said half of it was
black, I did not mean that half of the segments were turned on all the
time (whcih would lmost likley be a driver problem, not that that would
be any easier to fix). Nor do I mean that half the display is blank
(which would suggest bad connectios tat the zebra strip connectors).

No, what I mean is that the bottom part of the display is entirely
_black_. Even parts where there are no segments. Even when the unit is
turned off, when the battery is removed, or when the LCD glass is removed
from its holder.It's not an even line between the black part and the bit
that still works -- I could probably pass the display off as a silhouette
iamge of a munntain range :-).

IIRC, the LCD material rotates the plane of polarisation of light by
$\pi$/2, and there are corssed polarising filters on the outside of the
display (in this case they are not removeable). So normally the display
looks clear. If the LCD material laks out, you get the effect of looking
throguh a pair of crossed polaroids, i.e. black. Which is what I guess
has happened here.

Form the number of connections to the display, it must be multiplexed.
And thus I cna't drop in a nromal display (not even for the digits only).
Unless I can get the right part somehow -- and Fluke can no longer supply
it -- I am stuck.

-tony