Repaired Harbor Freight digital caliper

[P E Schoen]

I have two Harbor Freight digital calipers, item #47257, and I've had
problems with one of them especially, where the display will go blank. It
seemed to work sometimes if I squeezed the enclosure, and I thought it was a
bad battery or bad connection. But a fresh battery didn't work.

So I took it apart, which meant peeling off a foil backing to expose four
small phillips head screws, which removed the electronics module, and then I
removed the PC board with four even smaller phillips screws. The LCD display
connects to the board with a flexible conductive strip, which relies on
pressure to maintain contact. I cleaned it and the mating contacts on the
PCB, reassembled it, and it now works fine!

My house is always very humid and I think that's what caused the problem.
It's hell on all my tools. Everything is rusty or mildewed.

It's quite interesting to see the mechanism that is used to make
measurements. There is an array of PCB traces that are aligned with an array
of stripes along the length of the caliper, and (I assume) these create
pulses that are counted as the head is moved. But it also needs to know
which way the head is being moved. Probably something like a quadrature
encoder as used for rotary position sensing. I'll have to look it up.

Paul

 

[Jim Yanik]

"P E Schoen" <paul@pstech-inc.com> wrote in
news:a4_xq.6861$ov2.2972@newsfe10.iad:

I have two Harbor Freight digital calipers, item #47257, and I've had
problems with one of them especially, where the display will go blank.
It seemed to work sometimes if I squeezed the enclosure, and I thought
it was a bad battery or bad connection. But a fresh battery didn't
work.

So I took it apart, which meant peeling off a foil backing to expose
four small phillips head screws, which removed the electronics module,
and then I removed the PC board with four even smaller phillips
screws. The LCD display connects to the board with a flexible
conductive strip, which relies on pressure to maintain contact. I
cleaned it and the mating contacts on the PCB, reassembled it, and it
now works fine!

My house is always very humid and I think that's what caused the
problem. It's hell on all my tools. Everything is rusty or mildewed.

It's quite interesting to see the mechanism that is used to make
measurements. There is an array of PCB traces that are aligned with an
array of stripes along the length of the caliper, and (I assume) these
create pulses that are counted as the head is moved. But it also needs
to know which way the head is being moved. Probably something like a
quadrature encoder as used for rotary position sensing. I'll have to
look it up.

Paul

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

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

--
Jim Yanik
jyanik
at
localnet
dot com

 

[Jeff Liebermann]

On Sat, 19 Nov 2011 22:19:11 -0600, Jim Yanik <jyanik@abuse.gov>
wrote:

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

<http://siber-sonic.com/electronics/caig.html>
Sorta. The original Cramolin contained about 5% oleic acid, which is
great for removing surface oxidation, but is also mildly corrosive to
copper. The current version is DeOxit from Caig Labs. It comes in an
amazing variety of forms, and is allegedly non-corrosive.
<http://store.caig.com/s.nl/sc.2/.f>
The MSDS data shows the active ingredients as a "trade secret". Oh
well.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[N_Cook]

P E Schoen <paul@pstech-inc.com> wrote in message
news:a4_xq.6861$ov2.2972@newsfe10.iad...
I have two Harbor Freight digital calipers, item #47257, and I've had
problems with one of them especially, where the display will go blank. It
seemed to work sometimes if I squeezed the enclosure, and I thought it was a
bad battery or bad connection. But a fresh battery didn't work.

So I took it apart, which meant peeling off a foil backing to expose four
small phillips head screws, which removed the electronics module, and then I
removed the PC board with four even smaller phillips screws. The LCD display
connects to the board with a flexible conductive strip, which relies on
pressure to maintain contact. I cleaned it and the mating contacts on the
PCB, reassembled it, and it now works fine!

My house is always very humid and I think that's what caused the problem.
It's hell on all my tools. Everything is rusty or mildewed.

It's quite interesting to see the mechanism that is used to make
measurements. There is an array of PCB traces that are aligned with an array
of stripes along the length of the caliper, and (I assume) these create
pulses that are counted as the head is moved. But it also needs to know
which way the head is being moved. Probably something like a quadrature
encoder as used for rotary position sensing. I'll have to look it up.

Paul


++++

It is usually a Moire fringe counting mechanism. The system like when you
move along a street and look through a set of railings to another set of
railings and you see a moving "interference" pattern. Set 2 fine grills over
one another at slight relative angle and these fringes become wide enough to
be reliably counted by a relatively large opto device, 10 or more times
wider than the spacing between the grating lines

 

[William Sommerwerck]

"Jim Yanik" <jyanik@abuse.gov> wrote in message
news:Xns9FA2ED4AFED51jyaniklocalnetcom@216.168.3.44...

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

I assume the strip is carbon-impregnated rubber (or some synthetic polymer).
Cramolin/DeOxit remove surface oxidation. I don't the latter as being
compatible with the former.

 

[amdx]

On 11/19/2011 9:01 PM, P E Schoen wrote:

I have two Harbor Freight digital calipers, item #47257, and I've had
problems with one of them especially, where the display will go blank.
It seemed to work sometimes if I squeezed the enclosure, and I thought
it was a bad battery or bad connection. But a fresh battery didn't work.

That's why I like the Dial calipers vs Digital Calipers, no concern
about batteries or electronics.
(Dial Calipers, Item # 66541, Out of Stock)

Although a couple years ago HF had the 6" Digital calipers on sale for
$9.99, I bought two. They are still in the boxes and I use my Dial
calipers. I think I might give one away as a Christmas present.
Mikek

 

[N_Cook]

amdx <amdx@knologynotthis.net> wrote in message
news:4756b$4ec8f55d$18ec6dd7$12472@KNOLOGY.NET...

On 11/19/2011 9:01 PM, P E Schoen wrote:
I have two Harbor Freight digital calipers, item #47257, and I've had
problems with one of them especially, where the display will go blank.
It seemed to work sometimes if I squeezed the enclosure, and I thought
it was a bad battery or bad connection. But a fresh battery didn't work.


That's why I like the Dial calipers vs Digital Calipers, no concern
about batteries or electronics.
(Dial Calipers, Item # 66541, Out of Stock)

Although a couple years ago HF had the 6" Digital calipers on sale for
$9.99, I bought two. They are still in the boxes and I use my Dial
calipers. I think I might give one away as a Christmas present.
Mikek

I've never used the new-fangled ones - do you have to do a clean jaws, close
jaws, zero calibration check/0 reset ,every time you use them ? as the count
must be lost each time it is switched off

 

[Stormin Mormon]

Cleaned, how? Trichlor? WD? Cotton swab?

Have you considered something to reduce the humidity, like
vent fan, central AC, or dehumidifier?

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"P E Schoen" <paul@pstech-inc.com> wrote in message
news:a4_xq.6861$ov2.2972@newsfe10.iad...
I have two Harbor Freight digital calipers, item #47257, and
I've had
problems with one of them especially, where the display will
go blank. It
seemed to work sometimes if I squeezed the enclosure, and I
thought it was a
bad battery or bad connection. But a fresh battery didn't
work.

So I took it apart, which meant peeling off a foil backing
to expose four
small phillips head screws, which removed the electronics
module, and then I
removed the PC board with four even smaller phillips screws.
The LCD display
connects to the board with a flexible conductive strip,
which relies on
pressure to maintain contact. I cleaned it and the mating
contacts on the
PCB, reassembled it, and it now works fine!

My house is always very humid and I think that's what caused
the problem.
It's hell on all my tools. Everything is rusty or mildewed.

It's quite interesting to see the mechanism that is used to
make
measurements. There is an array of PCB traces that are
aligned with an array
of stripes along the length of the caliper, and (I assume)
these create
pulses that are counted as the head is moved. But it also
needs to know
which way the head is being moved. Probably something like a
quadrature
encoder as used for rotary position sensing. I'll have to
look it up.

Paul

 

[Dave Plumpe]

Not only do they remember where Zero is, they even keep track of any
movement that occurs while they're turned off. Smart little devils.

I find myself more & more reaching for the digital ones for the ease of
swapping between inches & millimeters.

-Dave
--
http://plumpe.home.mindspring.com
email: lastname@mindspring.com
ANTI-SPAM: To email, replace "lastname" with "plumpe"
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:jaatmo$4n4$1@dont-email.me...

I've never used the new-fangled ones - do you have to do a clean jaws,
close
jaws, zero calibration check/0 reset ,every time you use them ? as the
count
must be lost each time it is switched off

 

On Sun, 20 Nov 2011 06:41:03 -0600, amdx <amdx@knologynotthis.net>
wrote:

On 11/19/2011 9:01 PM, P E Schoen wrote:
I have two Harbor Freight digital calipers, item #47257, and I've had
problems with one of them especially, where the display will go blank.
It seemed to work sometimes if I squeezed the enclosure, and I thought
it was a bad battery or bad connection. But a fresh battery didn't work.


That's why I like the Dial calipers vs Digital Calipers, no concern
about batteries or electronics.
(Dial Calipers, Item # 66541, Out of Stock)

Although a couple years ago HF had the 6" Digital calipers on sale for
$9.99, I bought two. They are still in the boxes and I use my Dial
calipers. I think I might give one away as a Christmas present.
Mikek

I bought one of those and really like it. It seems comparable to
calipers costing many time more. The only problem is I have to remove
the battery when I am done using it or it is dead the next time I get
it out. I have a feeling that is why they were selling them for
$9.99. Fortuneately, it is easy to remove and reinsert the battery.

 

[N_Cook]

Dave Plumpe <lastname@mindspring.com> wrote in message
news:dcCdnbxH1tldnVTTnZ2dnUVZ_qednZ2d@earthlink.com...

Not only do they remember where Zero is, they even keep track of any
movement that occurs while they're turned off. Smart little devils.

I find myself more & more reaching for the digital ones for the ease of
swapping between inches & millimeters.

-Dave
--
http://plumpe.home.mindspring.com
email: lastname@mindspring.com
ANTI-SPAM: To email, replace "lastname" with "plumpe"
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:jaatmo$4n4$1@dont-email.me...

I've never used the new-fangled ones - do you have to do a clean jaws,
close
jaws, zero calibration check/0 reset ,every time you use them ? as the
count
must be lost each time it is switched off

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

 

[N_Cook]

<stans4@prolynx.com> wrote in message
news:0156c7a7-8bb2-4f32-922b-89bdd893a682@u6g2000vbg.googlegroups.com...
On Nov 20, 6:03 am, "N_Cook" <dive...@tcp.co.uk> wrote:

amdx <a...@knologynotthis.net> wrote in message

news:4756b$4ec8f55d$18ec6dd7$12472@KNOLOGY.NET...

On 11/19/2011 9:01 PM, P E Schoen wrote:
I have two Harbor Freight digital calipers, item #47257, and I've had
problems with one of them especially, where the display will go blank.
It seemed to work sometimes if I squeezed the enclosure, and I thought
it was a bad battery or bad connection. But a fresh battery didn't
work.

That's why I like the Dial calipers vs Digital Calipers, no concern
about batteries or electronics.
(Dial Calipers, Item # 66541, Out of Stock)

Although a couple years ago HF had the 6" Digital calipers on sale for
$9.99, I bought two. They are still in the boxes and I use my Dial
calipers. I think I might give one away as a Christmas present.
Mikek

I've never used the new-fangled ones - do you have to do a clean jaws,
close
jaws, zero calibration check/0 reset ,every time you use them ? as the
count
must be lost each time it is switched off

Used to be, they've improved things. On at least some, the count is
kept live and just the display is switched off. It all goes away when
batteries are switched, but that can be lived with.

Stan

+++

So that explains , down thread, the drawback of dying batteries when
switched "off"

 

On Nov 20, 6:03 am, "N_Cook" <dive...@tcp.co.uk> wrote:

amdx <a...@knologynotthis.net> wrote in message

news:4756b$4ec8f55d$18ec6dd7$12472@KNOLOGY.NET...

On 11/19/2011 9:01 PM, P E Schoen wrote:
I have two Harbor Freight digital calipers, item #47257, and I've had
problems with one of them especially, where the display will go blank..
It seemed to work sometimes if I squeezed the enclosure, and I thought
it was a bad battery or bad connection. But a fresh battery didn't work.

That's why I like the Dial calipers vs Digital Calipers, no concern
about batteries or electronics.
(Dial Calipers, Item # 66541, Out of Stock)

Although a couple years ago HF had the 6" Digital calipers on sale for
$9.99, I bought two. They are still in the boxes and I use my Dial
calipers. I think I might give one away as a Christmas present.
                                  Mikek

I've never used the new-fangled ones - do you have to do a clean jaws, close
jaws, zero calibration check/0 reset ,every time you use them ? as the count
must be lost each time it is switched off

Used to be, they've improved things. On at least some, the count is
kept live and just the display is switched off. It all goes away when
batteries are switched, but that can be lived with.

Stan

 

[Fred Abse]

On Sun, 20 Nov 2011 06:41:03 -0600, amdx wrote:

That's why I like the Dial calipers vs Digital Calipers, no concern
about batteries or electronics.

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

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

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

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

--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)

 

[Jamie]

N_Cook wrote:

stans4@prolynx.com> wrote in message
news:0156c7a7-8bb2-4f32-922b-89bdd893a682@u6g2000vbg.googlegroups.com...
On Nov 20, 6:03 am, "N_Cook" <dive...@tcp.co.uk> wrote:

amdx <a...@knologynotthis.net> wrote in message

news:4756b$4ec8f55d$18ec6dd7$12472@KNOLOGY.NET...


On 11/19/2011 9:01 PM, P E Schoen wrote:

I have two Harbor Freight digital calipers, item #47257, and I've had
problems with one of them especially, where the display will go blank.
It seemed to work sometimes if I squeezed the enclosure, and I thought
it was a bad battery or bad connection. But a fresh battery didn't

work.

That's why I like the Dial calipers vs Digital Calipers, no concern
about batteries or electronics.
(Dial Calipers, Item # 66541, Out of Stock)

Although a couple years ago HF had the 6" Digital calipers on sale for
$9.99, I bought two. They are still in the boxes and I use my Dial
calipers. I think I might give one away as a Christmas present.
Mikek

I've never used the new-fangled ones - do you have to do a clean jaws,

close

jaws, zero calibration check/0 reset ,every time you use them ? as the

count

must be lost each time it is switched off


Used to be, they've improved things. On at least some, the count is
kept live and just the display is switched off. It all goes away when
batteries are switched, but that can be lived with.

Stan

+++

So that explains , down thread, the drawback of dying batteries when
switched "off"


I have the HF digital calipers and I need to pull the battery when not

in use other wise, it'll be dead next time I need it. It seems to drain
quite fast.

Other than that, it seems to work very nicely..
Jamie

 

[Doug White]

greenpjs@neo.rr.com wrote in
news:e70ic7h9g57un7siiftqmdtkfp1tdej9bd@4ax.com:

On Sun, 20 Nov 2011 06:41:03 -0600, amdx <amdx@knologynotthis.net
wrote:

On 11/19/2011 9:01 PM, P E Schoen wrote:
I have two Harbor Freight digital calipers, item #47257, and I've
had problems with one of them especially, where the display will go
blank. It seemed to work sometimes if I squeezed the enclosure, and
I thought it was a bad battery or bad connection. But a fresh
battery didn't work.


That's why I like the Dial calipers vs Digital Calipers, no concern
about batteries or electronics.
(Dial Calipers, Item # 66541, Out of Stock)

Although a couple years ago HF had the 6" Digital calipers on sale for
$9.99, I bought two. They are still in the boxes and I use my Dial
calipers. I think I might give one away as a Christmas present.
Mikek

I bought one of those and really like it. It seems comparable to
calipers costing many time more. The only problem is I have to remove
the battery when I am done using it or it is dead the next time I get
it out. I have a feeling that is why they were selling them for
$9.99. Fortuneately, it is easy to remove and reinsert the battery.

The battery life in even high end calipers is highly variable. I have a
couple Mitutoyo calipers that are pretty good, but some of their
micrometers are terrible. I have an SPI micrometer that looks
suspiciously like a Chinese cheapo I have. They both need to have the
battery removed if you aren't actively using them. The SPI is a 24" job,
so it rarely gets used. There is no way the battery would last if I left
it in palce.

I discovered the hard way that the little cube electronic levels also eat
batteries, and they require a diet of the larger more expensive coin
cells (2032?). Most of my electronic measuring widgets use 357 style
button cells, and I buy them in quantity off eBay. Radio Shack is a real
ripoff for those things.

Doug White

 

[Jamie]

N_Cook wrote:

Dave Plumpe <lastname@mindspring.com> wrote in message
news:dcCdnbxH1tldnVTTnZ2dnUVZ_qednZ2d@earthlink.com...

Not only do they remember where Zero is, they even keep track of any
movement that occurs while they're turned off. Smart little devils.

I find myself more & more reaching for the digital ones for the ease of
swapping between inches & millimeters.

-Dave
--
http://plumpe.home.mindspring.com
email: lastname@mindspring.com
ANTI-SPAM: To email, replace "lastname" with "plumpe"
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:jaatmo$4n4$1@dont-email.me...

I've never used the new-fangled ones - do you have to do a clean jaws,
close
jaws, zero calibration check/0 reset ,every time you use them ? as the
count
must be lost each time it is switched off




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


And the engineer was correct in saying so.

Jamie

 

[Jeff Liebermann]

On Sun, 20 Nov 2011 13:38:36 -0000, "N_Cook" <diverse@tcp.co.uk>
wrote:

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

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

Do these digitally things require
the jaws closing before switching off ?

No.

How do they know of any movement of
the jaws when switched off elsewise?

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>

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.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Bob Engelhardt]

Jamie wrote:

I have the HF digital calipers and I need to pull the battery when not
in use other wise, it'll be dead next time I need it. It seems to drain
quite fast.
....

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>.

Bob

 

On Nov 19, 10:01 pm, "P E Schoen" <p...@pstech-inc.com> wrote:

I have two Harbor Freight digital calipers, item #47257, and I've had
problems with one of them especially, where the display will go blank. It
seemed to work sometimes if I squeezed the enclosure, and I thought it was a
bad battery or bad connection. But a fresh battery didn't work.

So I took it apart, which meant peeling off a foil backing to expose four
small phillips head screws, which removed the electronics module, and then I
removed the PC board with four even smaller phillips screws. The LCD display
connects to the board with a flexible conductive strip, which relies on
pressure to maintain contact. I cleaned it and the mating contacts on the
PCB, reassembled it, and it now works fine!

My house is always very humid and I think that's what caused the problem.
It's hell on all my tools. Everything is rusty or mildewed.

It's quite interesting to see the mechanism that is used to make
measurements. There is an array of PCB traces that are aligned with an array
of stripes along the length of the caliper, and (I assume) these create
pulses that are counted as the head is moved. But it also needs to know
which way the head is being moved. Probably something like a quadrature
encoder as used for rotary position sensing. I'll have to look it up.

Paul

http://www.biotele.com/digital_caliper.htm

--
Cheers,
James Arthur