Repaired Harbor Freight digital caliper

[DoN. Nichols]

...

I have one & the battery lasts quite a while (doesn't get used much).
Maybe a different model. Or a different batch. Or different spots on
the quality curve <G>.

Or different quality of battery as I just posted above.

Enjoy,
DoN.

 

[DoN. Nichols]

[ ... ]

An engineer told me never close the jaws of a micrometer or vernier calipers
for storage, leave the jaws open slightly.

A micrometer should never be stored closed. (Thermal changes in
dimensions can stress the components and reduce accuracy. Vernier
calipers should not have a problem as long as you don't *lock* them
closed -- either with the slide or the fine adjust slide.

Do these digitally things require
the jaws closing before switching off ? How do they know of any movement of
the jaws when switched off elsewise?

Most modern digital calipers only shut off the display, and keep
the counters and sensors powered up, so they can know where they are
when the display is switched back on -- and some will even switch the
display back on when it senses motion above some minimum value.

Enjoy,
DoN.

 

[DoN. Nichols]

True. With gear type calipers, the lubricating grease tends to
migrate to that position. If a sufficiently filthy environment, an
lump of dirt encrusted grease will be left in that position. If it
happens to be at 0.0, then it will be difficult to accurately
calibrate the mechanism.

But he said "Vernier calipers" which have no such mechanism.
Though people tend to lock the slides, so thermal stress distortion
could be a problem with them stored closed and locked.

There are also some minor reasons, such as
the tendency for two parallel surfaces to trap moisture between them
and rust.

Assuming non stainless steel jaws. (I've never seen calipers
with carbide faced jaws, unlike good micrometers.)

[ ... ]

Only the display is turned off. The pulse counting mechanism is still
operating and functional. The downside is that the battery will be
dead in about 6-9 months. Most include a spare LR44 battery. I had
to buy a pile of them to keep my calipers going. Somehow, the battery
is usually dead when I need to use them.

50 batteries for $3.75
<http://www.ebay.com/itm/220751739681>

There is your problem -- cheap cells. Don't use the LR44 (those
are alkaline batteries), use the SR44 and SR357 (Silver Oxide cells,
with much longer life). Then things will probably last at least six
months in storage. The SR44 and SR357 are pretty much interchangeable.
I don't even know why there are the two series -- though you will often
find them with both designators marked on the same cell or packaging.

I have an expensive set of Starett calipers (both metric and US). I
use them more often than the electronic variety, mostly out of habit.
My most useful measuring tools are my 6" pocket steel scale and a tape
measure.

While I tend to use the digital calipers by preference. Half as
many calipers needed to cover the metric and inch measurements.

Enjoy,
DoN.

 

[DoN. Nichols]

I've ignored the "Followup-To: " header, because I believe that this
also belongs in at least rec.crafts.metalworking, where I am following
it, and I would miss my own followup and any responses if it were kept
to a single group as requested.

I prefer a "proper" vernier. At least you can verify those by eye.

Depends on how old the eye is and how good the illumination is.

I never
did trust digital calipers to hold their zero and not skip under workshop
conditions, Half a lifetime dealing with incremental encoders has made me
wary.

The old B&S ones, which used glass encoders in the slot where
the rack gear would otherwise be were sensitive to coolant in the slot.
But the modern units seem to be quite good at not skipping.

I *might* trust a Mitutoyo digital caliper or height gage in inspection
room conditions.

I trust them (as much as a caliper *can* be trusted compared to
a micrometer) in shop conditions as well.

Dial calipers have all sorts of racks and gears to go sloppy.

Agreed -- or to pick up bits of swarf and skip.

I suppose nobody under fifty knows how to read a real vernier, or a slide
rule for that matter ;-(

I know how to use both -- but then I am (well) over fifty.

But there have been verniers on the thimbles of the better
micrometers much more recently than that, so presumably some of the
younger crowd know.

Enjoy,
DoN.

 

[J.B. Wood]

use Boeing Boeshield T-9 to prevent the rusting of your tools.

I wonder if Cramolin/DeOxit would work on the conductive strip?

Hello, and DeoxIT is the best thing I've ever come across for cleaning
and de-oxidizing electrical contacts. It also does wonders with
scratchy volume and tone pots and it'll be long while before you have to
apply it again. Sincerely,

 

[P E Schoen]

"Gunner Asch" wrote in message

Many 99c stores sell a flatpack of 5-10 standard 357 batteries
for a dollar.

I'm not sure I'd trust them in something any more expensive than a
flashlight. I have seen them corrode and leak. And the only thing the 99
cent store might be willing to do is give you another pack or refund your
dollar.

So I use 2 batteries a year. Or even 3. Im still way ahead of the
curve when SR44s are $3 each

I just purchased four genuine SR44s from an eBay store, for $3, including
first class mail shipping. The same company also has larger packs for quite
a bit less.
http://stores.ebay.com/RL-batterydepot?_trksid=p4340.l2563

I also measured the current draw on my calipers, and it's about 12.5 uA
either on or off. It seems to spike a bit when turned on. (So do I

They are specified at about 175 mAhr, according to http://www.sr44.com/, so
lifetime should be about 14000 hrs or 1.5 years, but the spec is for a low
voltage of 1.3V, which is probably below the limit of the electronics in the
caliper, at least for the low battery indicator.

Here is a handy list of the various sizes with different chemistry and their
mA-hr capacities: http://en.wikipedia.org/wiki/List_of_battery_sizes

Paul
www.pstech-inc.com

 

[amdx]

Harbor Freight Has the 6" dial Caliper on sale 11/24

http://www.harborfreight.com/previe...dium=email&utm_campaign=4711a&utm_source=1003

Mikek

 

[Jamie]

Harbor Freight Has the 6" dial Caliper on sale 11/24

http://www.harborfreight.com/previe...dium=email&utm_campaign=4711a&utm_source=1003


Mikek

Nice, I like the metal cutting saw they have there just off to the right..

Think I'll do a stop in for that.

Jamie

 

[amdx]

Nice, I like the metal cutting saw they have there just off to the right..

Think I'll do a stop in for that.

Jamie

Do note, it is pneumatic.
Fine if your setup for it.
Mikek

 

[DoN. Nichols]

[ ... ]

[ ... ]

Why bother including an on off switch?

It is an off switch to turn the *display* (only) back on. They
sometimes make it also turn the display back off to make people feel
better.

The auto-turn-off time of the display is usually good enough.

Enjoy,
DoN.

 

[DoN. Nichols]

[ ... ]

It's really not worth it for 1uA.

If I designed these, I'd shoot for 2uA active draw, like the
Mitutoyos, and set the battery low threshold at 1.1V (for alkalines).
The battery consumption is the biggest fault with these. Apart from
that, they're impressive.

I sometimes think about wiring up a "AAA" or solar cell and just
forgetting it, but for $0.50 a year it's not worth the trouble.

Actually -- there *are* some "solar powered" ones -- by Mitutoyo
IIRC. They would probably be excellent used daily in a well-illuminated
shop. In my shop, often dark for days at a time, until a project lures
me there, the replaceable batteries are a better choice.

I did recently get an auto-darkening welding hood from Harbor
Freight which is solar powered, and based on what I have read about them
dying if not used regularly, I've put mine on a folding workstool facing
out the window so it sees daylight to maintain the charge. I'll proably
eventually have to perform surgery and replace the rechargeable cells in
there. There is a temptation to provide a connection for an AC-powered
trickle charger so I can store it more conveniently. What would be
particularly nice would be an induction coupled charger like those for
electric toothbrushes. Just put it on a stand and expect it to be fully
charged when I come back.

If the charge is good enough to work on the first strike, it
should work fine for the rest of the day, because it will be getting a
charge boost from the arc -- close enough to vigorous sunlight.

Enjoy,
DoN.

 

[DoN. Nichols]

"Gunner Asch" wrote in message


I'm not sure I'd trust them in something any more expensive than a
flashlight.

Well ... I've paid more for *some* flashlights (typically
multi-LED ones) than for *some* digital calipers (import from a
hamfest), so it is a toss-up there.

I have seen them corrode and leak. And the only thing the 99
cent store might be willing to do is give you another pack or refund your
dollar.

If you are going to leave the calipers for more than a week,
pull the cell(s) and store them separately -- perhaps in a small zip-loc
baggie, so they don't damage anything else when leaking.

FWIW I've not seen the Silver Oxide ("SR" prefix) ones leak in anything
in which I have used them.

Enjoy,
DoN.

 

[P E Schoen]

"DoN. Nichols" wrote in message

It is an off switch to turn the *display* (only) back on. They
sometimes make it also turn the display back off to make
people feel better.

The auto-turn-off time of the display is usually good enough.

Still, there's no benefit to turning off the display, in this case. Might
just as well have it display "OFF".

I bought a high-end headlamp from Coleman a few years ago
http://www.coleman.com/coleman/ColemanCom/detail.asp?CategoryID=1116&product_id=2000000265#
and every time I went to use it the batteries (4 AA) were dead. I measured
the current draw when turned off, and it was something like 300 uA, which
should have provided 8000 hours (almost one year) for the 2500 mA-hr
batteries. But I was getting only a few weeks before finding them exhausted.
Maybe the current increased as the battery voltage dropped. I usually used
rechargeable NiMH and they might have been old and tired. But, still, there
is no reason for 300 uA standby current on a flashlight. Even if it had a
microcontroller, a typical PIC18F2420 draws only 11 uA while running, and
only 100 nanoamps in sleep mode! So, I just pop out one of the batteries
while I'm not using it. There's no easy place to install a switch.

Paul
www.muttleydog.com

 

[P E Schoen]

"DoN. Nichols" wrote in message

Well ... I've paid more for *some* flashlights (typically
multi-LED ones) than for *some* digital calipers (import
from a hamfest), so it is a toss-up there.

Yes, the Coleman headlamp I mentioned elsewhere lists for $50, and I paid
probably $20 on clearance, so I agree, in that case. But most flashlights
with coin cells are pretty much disposable.

If you are going to leave the calipers for more than a week,
pull the cell(s) and store them separately -- perhaps in a small
zip-loc baggie, so they don't damage anything else when leaking.

That's what I am going to do. There is a cutout in the foam of the caliper
case for a spare. I also put the other three cells in their original
packaging in there. I plan to use the calipers more now that I can depend on
them (and know how to fix them). Usually I don't do much precision
machining, and I have a cheap plastic dial caliper that is good to about
0.01" and is immune to humidity and most abuse.

FWIW I've not seen the Silver Oxide ("SR" prefix) ones leak in
anything in which I have used them.

I think the original cell in the HF caliper was actually alkaline, and
fortunately I had removed it (but kept in the case) when I had tried to fix
them a few years ago with no joy. When I opened it recently, the cell was
rusty and there was some liquid that had oozed out. I've also had some NiMH
AA cells that leaked. But probably the silver cells are better made and the
chemicals may be less aggressive. Now that I've found an on-line source with
good pricing I think I'll stick with them, although it's tempting to get the
Chinese copies for 10 cents each.

Paul

 

[DoN. Nichols]

[ ... ]

I saw a solar-powered Mitutoyo at a flea market and was intrigued, but
resisted. Something about having a glass window on a machine tool
close to all that hard steel just didn't sit well--it brought up
memories of scratched and broken watch crystals.

I've seen them only new, and decided that in my shop conditions,
they would not work very well.

OTOH, I paid $10 for most of my HF calipers. Those you can take
chances with. Using the 8x25mm solar panel from a $1 calculator, a
super capacitor for storage, and an LED as a regulator diode was my
notion. $2 in parts, $500 labor ;-).

O.K. Do you know the maximum voltage that the solar panel is
likely to produce? And the voltage drop on the LED? I know that
silicon diodes are typically between 600 mV and 750 mV. Also, any clues
as to the maximum voltage that the calipers can tolerate long term?

[ ... ]

Sounds like a LiIon cell. If so, those can't be allowed to go dead,
as you've surmised.

And -- they are supposedly not replaceable according to the
manual. (You've got to cut the package apart to get to them.) There
is a web page describing how someone opened one up and set a holder for
two AA cells outside the package. I'm really tempted to go for the
induction charger when I finally have to dig into mine. But it is
significantly less expensive than auto-darkening ones from MSC -- to the
point where three HF ones match the cost of one from MSC.

Enjoy,
DoN.

 

[DoN. Nichols]

"DoN. Nichols" wrote in message
news:[email protected]...

[ ... ]

That's what I am going to do. There is a cutout in the foam of the caliper
case for a spare. I also put the other three cells in their original
packaging in there. I plan to use the calipers more now that I can depend on
them (and know how to fix them). Usually I don't do much precision
machining, and I have a cheap plastic dial caliper that is good to about
0.01" and is immune to humidity and most abuse.

Except for certain solvents.

Good Luck,
DoN.

 

[Bob Engelhardt]

D1
.--|>|--+-----+----> (+) to caliper
+ | | |
.------. + | |
| | --- ---
| ---- | --- \ / ~~>
| | C1| ---
| ---- | | | LED (red)
| | | |
'------' | |
- | PV | |
'--------+-----+---> (-) to caliper

....

Doncha' need a current limiter on the LED?

Bob

 

[John S]

...

Doncha' need a current limiter on the LED?

Bob

Not if the PV cell's rated SC current is less than the max LED current
rating.

 

[Winston]

...

Doncha' need a current limiter on the LED?

Nup. It's a 'shunt regulator'.
http://en.wikipedia.org/wiki/Linear_regulator#Simple_zener_regulator

--Winston

 

[Winston]

[email protected] wrote:

(...)

I saw a solar-powered Mitutoyo at a flea market and was intrigued, but
resisted.

Next time, advise jump on it before someone else does.

I have two of those. They just keep working without
any issues. Well, except for turning off in low-light
situations. I just charge it up with the flashlight
and it works just fine. 'Way better than having to
run to the store for a $5 battery! They are fine tools
and have my highest recommendation.

--Winston