On 2009-04-09, James Waldby wrote:
On Thu, 09 Apr 2009 22:31:31 +0000, DoN. Nichols wrote:
...
Just for the fun of it -- let's see what I can remember picking
up at hamfests which might be of interest he
1) B&S 0-6" digital calipers (now not usable because they need
PX-13 mercury cells in a holder which would not be happy with any
modern cell, even if the slightly higher voltage does not harm
it.)
I'll try that someday.
...
A WeinCell MRB625 battery is supposed to be a proper $4 substitute
for a PX-13 mercury cell,
But since the B&S caliper needs *four* of them, that is a $16.00
replacement. (It is a "DIGIT-CAL II", FWIW.) (At least it is better
than some adaptors which were supposed to convert something like a SR357
to fit the PX-13 profile, which were selling for something like $25.00
each. Five Chinese calipers are cheaper enough of those to run the
caliper. :-)
according to various web pages like
http://www.pictureline.com/products/...B625_Battery/?
utm_source=google&utm_medium=shopping_engine&utm_c ampaign=google_products
and http://www.digitalfotoclub.com/sc/from-froogle.asp?
id=934228001&rf=froogle&dfdate=4_8_2009 or $40/dozen at
http://www.micro-tools.com/store/item_detail.aspx?ItemCode=MRB625-12
The voltage is right (1.35 V), but none of the web pages show a
side or angled view of the cell -- just a photo of it in a blister pack.
The shape of most cells is with a straight side, but the PX-13s
have (had) a profile like this (view with a fixed pitch font to avoid
distortion):
-
_--------_
_/__________\_
(_ _)
|__________|
+
And the cell holder which snaps onto the back of the caliper
*depends* on those side bulges to make contact.
They claim "WeinCell is a revolutionary new zinc/air battery
designed to replace environmentally-unfriendly (banned) mercury
batteries. ... Only WeinCells deliver exact voltage and stable
output consistent with mercury batteries." ... "the WeinCell is
not activated until the pull-tab is removed (removing batteries
from equipment and replacing tabs prolongs battery life)." ...
Snapping off the battery holder, removing two small Phillips
screws, removing the four cells, and relacing the tabs -- certainly
sounds convenient. :-) Well ... three of the four cells are held + side
up, visible through apertures in the holder, but (assuming that is the
surface with the holes to be covered) that still leaves one which
requires the same disassembly sequence.
And -- they don't say how long it takes to come up to full
voltage after removing the tabs each time. :-)
Since this does not require the sable voltage that an exposure
meter (or one built into a camera), I'm more likely to machine a
replacement holder using two CR3032 3V cells, with a silicon diode and
two germanium diodes in series with them (for a total of about 1 V drop,
since four mercury cells add up to 5 V, and the CR3032s are 3V each.)
I'll first check how forgiving it is using a bench power supply to apply
a full 6 V (working my way up from 5 V) and see whether it has problems
with that.
I've been considering this for a long time. I've got a Starrett
A Mitutoyo digital caliper, a Chinese manufacture one, and the 12"
Mitutoyo one.
But the interesting thing about this one is that it uses the
same technology that the glass scales for DROs and for CNC feedback use,
a barcode vacuum-plated on glass in the slot where the rack gear would
be on a dial caliper, a pair of barcodes 1/4 out of phase mounted to the
carrier, two leds and two photo-detectors. (The LEDs are probably why
it kills batteries more quickly -- but at least when you press "off", it
is *truly* off. :-)
Needless to say -- at this point I don't really *need* to have
this working -- but it is a neat enough design so I would *like* to have
it working. :-)
"The WeinCELL MRB625 batteries last much longer than hearing
aid batteries, some times up to a year. To achieve this longer
life, the MRB625 used a proprietary electrolyte and has only
two small air holes, instead of the 7 larger holes found in
standard hearing aid batteries.", per
So -- why don't they bother showing the form of the case?
http://www.mdbattery.com/product_info.php?products_id=153&cPath=134
Hmm ... these may be right -- if the shape is as described, and
if the caliper can tolerate 6.20 V.
I really need to contact Wein first and see whether they are
truly the shape of the PX-13 cells.
Enjoy,
DoN.
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