On Nov 20, 8:45*pm, Jeff Liebermann wrote:
On Sun, 20 Nov 2011 16:47:25 -0800 (PST), "Ron D." wrote:

I have a cheap Caliper too and it recently went flakey.

I did my standard trick: *Remove battery. *Short battery contacts:
Insert new battery. *Worked.

My cheap electronic caliper goes nuts when I transmit on UHF anywhere
near it. *However, it doesn't require the battery removal ordeal to
recover. *I just reset to zero and continue.

Mine uses an LR44 and you HAVE TO use an LR44, not a substitute
battery that you can get a Radio Shack.
Mechanically they are not the same.

I beg to differ. *The general package name is LR44 in an 11.6mm dia x
5.4mm thick package alkaline cell. *There are slight variations, but
the IEC LR1154 equivalents (LR44/LR154, A76, 157/303/357) are all the
same size. *Where you can have problems is that the SR44/SR1154 silver
oxide cells come in the same package. *They have about 50% more
capacity and a much flatter discharge curve. *Some of the cheapo
calipers crap out below about 1.4V. *The alkaline battery has plenty
of capacity left at 1.4V, but the caliper doesn't want to run. *If
your caliper cames with a silver-oxide cell, it should probably use
silver oxide batteries. *If it came with alkaline and has a short
battery life, it might be worthwhile trying silver-oxide. *If you're
ambitious, it might be useful to run the caliper off a bench power
supply and check how low a voltage will work.

I just measured a Harbor Freight (Chinese) 8-incher.

Drain: 13.5uA (off), 14.5uA (on)
Battery low threshold (blinking display): 1.37V
Lowest operating voltage: 1.01V

So, it's clearly made for silver-oxide cells. The battery low
threshold is set appropriately for a silver oxide cell (e.g. SR-44).

It's a lousy threshold for using alkalines--they're barely broken in
at that voltage.

14.5uA means a year from a silver oxide cell--that's not horrible.

--
Cheers,
James Arthur