Hi.

If anyone's considering buying one of those expensive Salter Electronic
Kitchen Scales, you'll probably want to be aware of a design problem
that messes up the accuracy. You can work around the problem, and still
get accurate readings, but it is a rather daft fault. This is what I've
put on Salter's feedback form, and I'm waiting for their reply:

-------------------- Begin quote --------------------

I bought one of your 1004 "Electronic kitchen scales with stainless
steel platform" about a year ago and I was very happy with it. However,
it developed a fault, and I had it replaced under guarantee with a new
one. Unfortunately, I am far from happy with the behaviour of the new
scale and I have found what I believe is a serious design fault that has
been introduced into it.

I noticed that when I was measuring powders or liquids, that I was
ending up with quantities that were visibly too large for the displayed
weight. When I then transferred the powder or liquid to some old
balance scales that were cumbersome but accurate, I found that the
quantities were as much as 20% too high.

I then investigated the problem, and found that the scale misreads if
the powder or liquid is added too slowly. I presume that this is because
a software change has been introduced into the scale's electronics to
try to compensate for drifting errors in the weight sensors.

Didn't it occur to the designers that the natural way to use a kitchen
scale is to put a bowl on the scale, zero it, pour in most of the
quantity of powder that is required, then slowly add the rest to bring
it up to the target weight. If you do this however, the scale
under-reads. The only way to get around this behaviour, and to get a
reasonably accurate reading, is to press a spoon into the powder for a
moment, when adding small quantities, to make a large change to the
weight which disables this software trick.

I have to say that this has made the scale much harder to use and is
very irritating. I'd like to return the scale for one that behaves the
way that the old scale did. Before I do however, I'd like to know if any
are available, or do all of your kitchen scales now have this misleading
drift compensation thing?

-------------------- End quote --------------------

--
Farry

On Sun, 25 Jan 2004 10:16:35 GMT, Farry
> wrote:

| Hi.
|
| If anyone's considering buying one of those expensive Salter Electronic
| Kitchen Scales, you'll probably want to be aware of a design problem
| that messes up the accuracy. You can work around the problem, and still
| get accurate readings, but it is a rather daft fault. This is what I've
| put on Salter's feedback form, and I'm waiting for their reply:

I use the Salter electronic Aquatronic model number 3007, all plastic, and
find it everything I had hoped. I have checked the accuracy a few times
and found it fine.

Dave F

Dave Fawthrop > wrote:

>I use the Salter electronic Aquatronic model number 3007, all plastic, and
>find it everything I had hoped. I have checked the accuracy a few times
>and found it fine.

I would also have said that, but of the scale I bought a year ago,
rather than the "compensated" scale. When did you buy yours?

--
Farry

On Sun, 25 Jan 2004 10:38:41 GMT, Farry
> wrote:

| Dave Fawthrop > wrote:
|
| >I use the Salter electronic Aquatronic model number 3007, all plastic, and
| >find it everything I had hoped. I have checked the accuracy a few times
| >and found it fine.
|
| I would also have said that, but of the scale I bought a year ago,
| rather than the "compensated" scale. When did you buy yours?

Sounds as if yours has a simple mechanical fault. Perhaps crud has built up
inside, or the platform has got twisted.

I have had mine about ?2? years.

I have just tried adding sugar slowly, no problem.

Dave F

Dave Fawthrop > wrote:

>On Sun, 25 Jan 2004 10:38:41 GMT, Farry
> wrote:
>
>| Dave Fawthrop > wrote:
>|
>| >I use the Salter electronic Aquatronic model number 3007, all plastic, and
>| >find it everything I had hoped. I have checked the accuracy a few times
>| >and found it fine.
>|
>| I would also have said that, but of the scale I bought a year ago,
>| rather than the "compensated" scale. When did you buy yours?
>
>Sounds as if yours has a simple mechanical fault. Perhaps crud has built up
>inside, or the platform has got twisted.
>
>I have had mine about ?2? years.
>
>I have just tried adding sugar slowly, no problem.

OK, the model 3007 is not displayed on their website, so I guess it's an
old model and predates the compensation trick.

As I said, it's the brand new scale that's got the problem. It's almost
certainly designed into the software because I can think of no way that
a fault could introduce behaviour like that, but I can think of why a
software designer would want to add that compensation, if he didn't
properly think through the consequences.

--
Farry

On Sun, 25 Jan 2004 11:12:35 GMT, Farry
> wrote:

| Dave Fawthrop > wrote:
|
| >On Sun, 25 Jan 2004 10:38:41 GMT, Farry
| > wrote:
| >
| >| Dave Fawthrop > wrote:
| >|
| >| >I use the Salter electronic Aquatronic model number 3007, all plastic, and
| >| >find it everything I had hoped. I have checked the accuracy a few times
| >| >and found it fine.
| >|
| >| I would also have said that, but of the scale I bought a year ago,
| >| rather than the "compensated" scale. When did you buy yours?
| >
| >Sounds as if yours has a simple mechanical fault. Perhaps crud has built up
| >inside, or the platform has got twisted.
| >
| >I have had mine about ?2? years.
| >
| >I have just tried adding sugar slowly, no problem.
|
| OK, the model 3007 is not displayed on their website, so I guess it's an
| old model and predates the compensation trick.
|
| As I said, it's the brand new scale that's got the problem. It's almost
| certainly designed into the software because I can think of no way that
| a fault could introduce behaviour like that, but I can think of why a
| software designer would want to add that compensation, if he didn't
| properly think through the consequences.

Just reread your original post.

As both an ex-engineer and a software writer, it still looks like a
mechanical problem, and not a software problem. My guess is that the
platform is dragging, catching or juddering on something.
Mechanical problems sometimes build up slowly, or suddenly appear.
Software problems are either there, or not there, all the time.

Dave F

"Farry" > wrote in message
...
> Dave Fawthrop > wrote:
>
> >On Sun, 25 Jan 2004 10:38:41 GMT, Farry
> > wrote:
> >
> >| Dave Fawthrop > wrote:
> >|
> >| >I use the Salter electronic Aquatronic model number 3007, all plastic,
and
> >| >find it everything I had hoped. I have checked the accuracy a few
times
> >| >and found it fine.
> >|
> >| I would also have said that, but of the scale I bought a year ago,
> >| rather than the "compensated" scale. When did you buy yours?
> >
> >Sounds as if yours has a simple mechanical fault. Perhaps crud has built
up
> >inside, or the platform has got twisted.
> >
> >I have had mine about ?2? years.
> >
> >I have just tried adding sugar slowly, no problem.
>
> OK, the model 3007 is not displayed on their website, so I guess it's an
> old model and predates the compensation trick.
>
> As I said, it's the brand new scale that's got the problem. It's almost
> certainly designed into the software because I can think of no way that
> a fault could introduce behaviour like that, but I can think of why a
> software designer would want to add that compensation, if he didn't
> properly think through the consequences.
>
> --
> Farry

The kitchen scales use strain guages as the weight transducer. Although
these are not linear in output (which is compensated), they do not exhibit
the fault you describe. Its more likely to be a fault in the weighing
platform suspension mechanism sticking (imagine a shaft going through a hole
and rubbing on the side). Probably a batch manufacturing problem. Check the
batch number of your model and take it back for exchange, making sure the
new one is from a different batch/manufacture date.

Dave

Dave Fawthrop > wrote:

>Just reread your original post.
>
>As both an ex-engineer and a software writer, it still looks like a
>mechanical problem, and not a software problem. My guess is that the
>platform is dragging, catching or juddering on something.
>Mechanical problems sometimes build up slowly, or suddenly appear.
>Software problems are either there, or not there, all the time.

OK, I've just done this.

1. Place clean mirror on worktop to make a perfectly flat surface.

2. Make sure both sides of scale are clean, and place on mirror.

3. Zero scale.

4. Put cereal bowl on scale - 274g.

5. Add tablespoon (20g) of muesli - 294g.

6. Tip out muesli and put bowl back - 274g.

7. Add same muesli back very slowly over 1 minute - 276g.
i.e. it's somehow lost 18g.

8. Tip out muesli and put bowl back - 256g.
Still 18g down.

9. Remove bowl - and scale shows "----" (below zero).

This is quite repeatable. The scale is accurate and consistent, and does
not drift even over several minutes, PROVIDED that the weight changes
are swift.

QED?

--
Farry

On Sun, 25 Jan 2004 13:08:45 GMT, Farry
> wrote:

| Dave Fawthrop > wrote:
|
| >Just reread your original post.
| >
| >As both an ex-engineer and a software writer, it still looks like a
| >mechanical problem, and not a software problem. My guess is that the
| >platform is dragging, catching or juddering on something.
| >Mechanical problems sometimes build up slowly, or suddenly appear.
| >Software problems are either there, or not there, all the time.
|
| OK, I've just done this.
|
| 1. Place clean mirror on worktop to make a perfectly flat surface.
|
| 2. Make sure both sides of scale are clean, and place on mirror.
|
| 3. Zero scale.
|
| 4. Put cereal bowl on scale - 274g.
|
| 5. Add tablespoon (20g) of muesli - 294g.
|
| 6. Tip out muesli and put bowl back - 274g.
|
| 7. Add same muesli back very slowly over 1 minute - 276g.
| i.e. it's somehow lost 18g.
|
| 8. Tip out muesli and put bowl back - 256g.
| Still 18g down.
|
| 9. Remove bowl - and scale shows "----" (below zero).
|
| This is quite repeatable. The scale is accurate and consistent, and does
| not drift even over several minutes, PROVIDED that the weight changes
| are swift.
|
| QED?

Judder!
A well known mechanical engineering problem. Often experianced in car
brakes when the car vibrates when braking.
Friction varies with position and time, not like they teach you in school.
I have seen it in lots of things but never in scales.

Take it back and demonstrate the problem, Even a shop assistant should
understand that it does not work properly. Get a different model, it may
be a batch problem.

Dave F

Farry wrote:
>> 6. Tip out muesli and put bowl back - 274g.
>
> 7. Add same muesli back very slowly over 1 minute - 276g.
> i.e. it's somehow lost 18g.
>
> 8. Tip out muesli and put bowl back - 256g.
> Still 18g down.
>
> 9. Remove bowl - and scale shows "----" (below zero).
> QED?

Interesting. Some recipes call for a half dozen ingreditents and I add them
one a t a time. It can easily take a few minutes as you put one away and
get out the next. That would be a problem.

--
Ed

http://pages.cthome.net/edhome

Dave Fawthrop > wrote:

>Judder!
>A well known mechanical engineering problem. Often experianced in car
>brakes when the car vibrates when braking.
>Friction varies with position and time, not like they teach you in school.
>I have seen it in lots of things but never in scales.
>
>Take it back and demonstrate the problem, Even a shop assistant should
>understand that it does not work properly. Get a different model, it may
>be a batch problem.

I can't take it back to the shop, because I bought the original a year
ago, and now I've just got a replacement under guarantee by post from
Salter. So I'll wait for the response from Salter to my query, first.

I appreciate that it's hard to believe that this behaviour could be
designed in. OK, next experiment.

I repeat the process of adding muesli to the bowl three times, without
zeroing the scale, and weigh the bowl each time. It starts at 274g, then
it's 254g, then 236g, then 216g. i.e. 18-20g down each time leaving it
58g low. And since I completely remove the bowl from the scale to tip
out the muesli each time, that should have sorted out any judder.

--
Farry

"Edwin Pawlowski" > wrote:

>Interesting. Some recipes call for a half dozen ingreditents and I add them
>one a t a time. It can easily take a few minutes as you put one away and
>get out the next. That would be a problem.

Actually, that can be a problem, but not for the reason that I've
outlined. If you leave the scale without changing the weight on it, the
display will switch off after a couple of minutes to save power, and you
can't switch it on again without zeroing the scale. You have to remember
to dab it with your finger every minute to keep it alive, and the
displayed weight will remain consistent. Just don't pour in an
ingredient too slowly.

--
Farry

"Dave Gibson" > wrote:

>The kitchen scales use strain guages as the weight transducer. Although
>these are not linear in output (which is compensated), they do not exhibit
>the fault you describe. Its more likely to be a fault in the weighing
>platform suspension mechanism sticking (imagine a shaft going through a hole
>and rubbing on the side). Probably a batch manufacturing problem. Check the
>batch number of your model and take it back for exchange, making sure the
>new one is from a different batch/manufacture date.

Unfortunately, there's no batch number, the model number is the same,
and the appearance of the old and new scales are identical, as far as I
can remember. I believe that I've eliminated the possibility of the
mechanism sticking mechanically, so that leaves either a bizarre
electronic fault, or more likely in my opinion, an ill-thought attempt
to compensate for drift in the strain gauge.

--
Farry

On Sun, 25 Jan 2004 16:27:49 GMT, Farry
> wrote:


| I can't take it back to the shop, because I bought the original a year
| ago, and now I've just got a replacement under guarantee by post from
| Salter. So I'll wait for the response from Salter to my query, first.

Salter offer a 10 year guarantee
http://www.salterhousewares.com/page...x.asp?code=14#
and click on 1004.

Why not get it swapped for a 3007 which they still sell on
http://www.salterhousewares.com/page...e=14&offset=2#
Not as fancy but it works OK.

Better than stripping what you have and risking buggering it up.

--
Dave Fawthrop >
Sick and tired of Junk Snail Mail? Register your family
surname and address with www.mpsonline.org.uk

Dave Fawthrop > wrote in
:

> On Sun, 25 Jan 2004 13:08:45 GMT, Farry
> > wrote:
>
>| Dave Fawthrop > wrote:
>|
>| >Just reread your original post.
>| >
>| >As both an ex-engineer and a software writer, it still looks like a
>| >mechanical problem, and not a software problem. My guess is that
>| >the platform is dragging, catching or juddering on something.
>| >Mechanical problems sometimes build up slowly, or suddenly appear.
>| >Software problems are either there, or not there, all the time.
>|
>| OK, I've just done this.
>|
>| 1. Place clean mirror on worktop to make a perfectly flat surface.
>|
>| 2. Make sure both sides of scale are clean, and place on mirror.
>|
>| 3. Zero scale.
>|
>| 4. Put cereal bowl on scale - 274g.
>|
>| 5. Add tablespoon (20g) of muesli - 294g.
>|
>| 6. Tip out muesli and put bowl back - 274g.
>|
>| 7. Add same muesli back very slowly over 1 minute - 276g.
>| i.e. it's somehow lost 18g.
>|
>| 8. Tip out muesli and put bowl back - 256g.
>| Still 18g down.
>|
>| 9. Remove bowl - and scale shows "----" (below zero).
>|
>| This is quite repeatable. The scale is accurate and consistent, and
>| does not drift even over several minutes, PROVIDED that the weight
>| changes are swift.
>|
>| QED?
>
> Judder!
> A well known mechanical engineering problem. Often experianced in car
> brakes when the car vibrates when braking.
> Friction varies with position and time, not like they teach you in
> school. I have seen it in lots of things but never in scales.
>
> Take it back and demonstrate the problem, Even a shop assistant should
> understand that it does not work properly. Get a different model,
> it may be a batch problem.
>
> Dave F
>

Not convinced Dave. At least it must be coupled with a software fault
if the bowl showed different weights at different times.

--
Adrian

Farry > wrote in
:

> "Edwin Pawlowski" > wrote:
>
>>Interesting. Some recipes call for a half dozen ingreditents and I
>>add them one a t a time. It can easily take a few minutes as you put
>>one away and get out the next. That would be a problem.
>
> Actually, that can be a problem, but not for the reason that I've
> outlined. If you leave the scale without changing the weight on it,
> the display will switch off after a couple of minutes to save power,
> and you can't switch it on again without zeroing the scale. You have
> to remember to dab it with your finger every minute to keep it alive,
> and the displayed weight will remain consistent. Just don't pour in an
> ingredient too slowly.
>

So, what is the advantage of digital scales over my springy ones?

--
Adrian

Usually strain gaged loadcells have very small deflections. So movement
sticking is unlikely to be an issue.

Software issue may relate to low cost analog to digital conversion, reading
frequency, etc.

"Dave Gibson" > wrote in message
...
>
> "Farry" > wrote in message
> ...
> > Dave Fawthrop > wrote:
> >
> > >On Sun, 25 Jan 2004 10:38:41 GMT, Farry
> > > wrote:
> > >
> > >| Dave Fawthrop > wrote:
> > >|
> > >| >I use the Salter electronic Aquatronic model number 3007, all
plastic,
> and
> > >| >find it everything I had hoped. I have checked the accuracy a few
> times
> > >| >and found it fine.
> > >|
> > >| I would also have said that, but of the scale I bought a year ago,
> > >| rather than the "compensated" scale. When did you buy yours?
> > >
> > >Sounds as if yours has a simple mechanical fault. Perhaps crud has
built
> up
> > >inside, or the platform has got twisted.
> > >
> > >I have had mine about ?2? years.
> > >
> > >I have just tried adding sugar slowly, no problem.
> >
> > OK, the model 3007 is not displayed on their website, so I guess it's an
> > old model and predates the compensation trick.
> >
> > As I said, it's the brand new scale that's got the problem. It's almost
> > certainly designed into the software because I can think of no way that
> > a fault could introduce behaviour like that, but I can think of why a
> > software designer would want to add that compensation, if he didn't
> > properly think through the consequences.
> >
> > --
> > Farry
>
> The kitchen scales use strain guages as the weight transducer. Although
> these are not linear in output (which is compensated), they do not exhibit
> the fault you describe. Its more likely to be a fault in the weighing
> platform suspension mechanism sticking (imagine a shaft going through a
hole
> and rubbing on the side). Probably a batch manufacturing problem. Check
the
> batch number of your model and take it back for exchange, making sure the
> new one is from a different batch/manufacture date.
>
> Dave
>
>

In message >, Adrian Tupper
> writes
>Farry > wrote in
:
>
>> "Edwin Pawlowski" > wrote:
>>
>>>Interesting. Some recipes call for a half dozen ingreditents and I
>>>add them one a t a time. It can easily take a few minutes as you put
>>>one away and get out the next. That would be a problem.
>>
>> Actually, that can be a problem, but not for the reason that I've
>> outlined. If you leave the scale without changing the weight on it,
>> the display will switch off after a couple of minutes to save power,
>> and you can't switch it on again without zeroing the scale. You have
>> to remember to dab it with your finger every minute to keep it alive,
>> and the displayed weight will remain consistent. Just don't pour in an
>> ingredient too slowly.
>>
>
>So, what is the advantage of digital scales over my springy ones?
>
Well said. I have Dualit mechanical scales, which come up trumps all
the time. The only problem is that the bowl is large (not a problem)
and round (a problem if you are tipping the contents into a smaller
bowl).
--
June Hughes

> >
>
> So, what is the advantage of digital scales over my springy ones?
>
> --
> Adrian

Greater accuracy.

Fred
The Good Gourmet
http://www.thegoodgourmet.com

Fred wrote:
>> So, what is the advantage of digital scales over my springy ones?
>>
>> --
>> Adrian
>
> Greater accuracy.
>
> Fred
> The Good Gourmet
> http://www.thegoodgourmet.com

In some cases, but not all. A good balance scale will be far more accurate
than a digital, but some spring scales are junk also. It may have changed,
but a few years ago, Ohaus tripe beam balance scales were allowed for gold
assay, but not the digital.

--
Ed

http://pages.cthome.net/edhome

In uk.food+drink.misc Fred > wrote:
>
> > >
> >
> > So, what is the advantage of digital scales over my springy ones?
> >
> > --
> > Adrian
>
> Greater accuracy.
>
Accuracy of indication maybe but the mechanics of transferring the
measurement to the electronics are just the same as for any
'mechanical' scales.

--
Chris Green

> wrote in message
...
> In uk.food+drink.misc Fred > wrote:
> >
> > > >
> > >
> > > So, what is the advantage of digital scales over my springy ones?
> > >
> > > --
> > > Adrian
> >
> > Greater accuracy.
> >
> Accuracy of indication maybe but the mechanics of transferring the
> measurement to the electronics are just the same as for any
> 'mechanical' scales.
>
> --
> Chris Green

I do not believe that is true. The electronic balances that I am familiar
with use some sort of solid state pressure transducer that converts the
weight into a voltage. Spring balances use the weight of the food against a
spring to move the indicator dial. Very different processes.

Peter G. Aitken

On Mon, 26 Jan 2004 14:44:09 GMT, "Peter Aitken" >
wrote:

| > wrote in message
| ...
| > In uk.food+drink.misc Fred > wrote:
| > >
| > > > >
| > > >
| > > > So, what is the advantage of digital scales over my springy ones?
| > > >
| > > > --
| > > > Adrian
| > >
| > > Greater accuracy.
| > >
| > Accuracy of indication maybe but the mechanics of transferring the
| > measurement to the electronics are just the same as for any
| > 'mechanical' scales.
| >
| > --
| > Chris Green
|
| I do not believe that is true. The electronic balances that I am familiar
| with use some sort of solid state pressure transducer that converts the
| weight into a voltage. Spring balances use the weight of the food against a
| spring to move the indicator dial. Very different processes.

The movement caused by weight on the scales, in my Salter scales of a
different model is 1-2mm which is quite enough for friction effects to
cause problems.

Dave F

In uk.food+drink.misc Peter Aitken > wrote:
> > wrote in message
> ...
> > In uk.food+drink.misc Fred > wrote:
> > >
> > > > >
> > > >
> > > > So, what is the advantage of digital scales over my springy ones?
> > > >
> > > > --
> > > > Adrian
> > >
> > > Greater accuracy.
> > >
> > Accuracy of indication maybe but the mechanics of transferring the
> > measurement to the electronics are just the same as for any
> > 'mechanical' scales.
> >
> > --
> > Chris Green
>
> I do not believe that is true. The electronic balances that I am familiar
> with use some sort of solid state pressure transducer that converts the
> weight into a voltage. Spring balances use the weight of the food against a
> spring to move the indicator dial. Very different processes.
>
How about balance type mechanical scales, very accurate and very easy
to zero set correctly. I agree that a different mechanical basis for
different sorts of scales will affect the accuracy. With electronic
scales the mechanics of the interface to the pressure transducer (if
that's what is used) will define the accuracy. It's very easy to be
fooled by a digital display into believing that all the digits it
displays represent actual accuracy.

--
Chris Green

> wrote in message
...
> In uk.food+drink.misc Peter Aitken > wrote:
> > > wrote in message
> > ...
> > > In uk.food+drink.misc Fred > wrote:
> > > >
> > > > > >
> > > > >
> > > > > So, what is the advantage of digital scales over my springy ones?
> > > > >
> > > > > --
> > > > > Adrian
> > > >
> > > > Greater accuracy.
> > > >
> > > Accuracy of indication maybe but the mechanics of transferring the
> > > measurement to the electronics are just the same as for any
> > > 'mechanical' scales.
> > >
> > > --
> > > Chris Green
> >
> > I do not believe that is true. The electronic balances that I am
familiar
> > with use some sort of solid state pressure transducer that converts the
> > weight into a voltage. Spring balances use the weight of the food
against a
> > spring to move the indicator dial. Very different processes.
> >
> How about balance type mechanical scales, very accurate and very easy
> to zero set correctly.

I have some balance scales but what with parallax etc., it's difficult to
see when the pointer is exactly at the mark (at least on mine). I use my
Salter electronic all the time now and I always press the scale after adding
the last couple of grams to make certain that the reading is OK. From what
has been said here, I think that I might have to invest in some weights to
check their accuracy.
My only complaint is the cost of the batteries and, to me, their relatively
short life-span.
Graham

"Fred" > wrote in news:QLZQb.21236
:

>
>> >
>>
>> So, what is the advantage of digital scales over my springy ones?
>>
>> --
>> Adrian
>
> Greater accuracy.

Not according to the OP. And just how accurate does one need to be?
All the recipes I know have quantities given in whole oz or sometimes
half-oz. My scales are accurate enough for that.

--
Adrian

"Edwin Pawlowski" > wrote:

>Fred wrote:
>
>>> So, what is the advantage of digital scales over my springy ones?
>>> --
>>> Adrian
>>
>> Greater accuracy.
>
>In some cases, but not all. A good balance scale will be far more accurate
>than a digital, but some spring scales are junk also. It may have changed,
>but a few years ago, Ohaus tripe beam balance scales were allowed for gold
>assay, but not the digital.

Balance scales are very accurate, but they are a bit cumbersome. I must
admit that even having to work around the problem that I've described
with the electronic scales, they are still easier to use than my old
balance scales.

--
Farry

Adrian Tupper wrote:

> Not according to the OP. And just how accurate does one need
> to be? All the recipes I know have quantities given in whole oz
> or sometimes half-oz. My scales are accurate enough for that.

Maybe he's using the scale to weigh illegal drugs,
in which case he certainly might care about fractions
of an ounce. He couldn't just say that's what he's doing
in a Usenet newsgroup.

Mark Thorson > wrote:

>Maybe he's using the scale to weigh illegal drugs,
>in which case he certainly might care about fractions
>of an ounce. He couldn't just say that's what he's doing
>in a Usenet newsgroup.

Fol de rol.

Farry > wrote in message >. ..
> Hi.
>
> If anyone's considering buying one of those expensive Salter Electronic
> Kitchen Scales, you'll probably want to be aware of a design problem
> that messes up the accuracy. You can work around the problem, and still
> get accurate readings, but it is a rather daft fault. This is what I've
> put on Salter's feedback form, and I'm waiting for their reply:
<snip>

Just FYI. The proper way to weigh solids is to add an excess to the
scale and then *remove* the material until you reach the desired
weight.

-L.

Farry > wrote in message >. ..
> "Dave Gibson" > wrote:
>
> >The kitchen scales use strain guages as the weight transducer. Although
> >these are not linear in output (which is compensated), they do not exhibit
> >the fault you describe. Its more likely to be a fault in the weighing
> >platform suspension mechanism sticking (imagine a shaft going through a hole
> >and rubbing on the side). Probably a batch manufacturing problem. Check the
> >batch number of your model and take it back for exchange, making sure the
> >new one is from a different batch/manufacture date.
>
> Unfortunately, there's no batch number, the model number is the same,
> and the appearance of the old and new scales are identical, as far as I
> can remember. I believe that I've eliminated the possibility of the
> mechanism sticking mechanically, so that leaves either a bizarre
> electronic fault, or more likely in my opinion, an ill-thought attempt
> to compensate for drift in the strain gauge.

Jumping in late here, I think if you go back and look at the data you
posted from your experiment, all you've really shown is that you get
different results if the weight is added suddenly (whether bowl or
muesli) or gradually. By far the easiest and most likely explanation
of this is friction: there's something "sticky" in the mechanics
between bowl and strain gauge and the friction is not overcome when
weight is added very slowly. I may have used different words but in
effect, I'm with Dave here.

- Mark W.

On 27 Jan 2004 08:54:22 -0800, (-L.) wrote:

| Farry > wrote in message >. ..
| > Hi.
| >
| > If anyone's considering buying one of those expensive Salter Electronic
| > Kitchen Scales, you'll probably want to be aware of a design problem
| > that messes up the accuracy. You can work around the problem, and still
| > get accurate readings, but it is a rather daft fault. This is what I've
| > put on Salter's feedback form, and I'm waiting for their reply:
| <snip>
|
| Just FYI. The proper way to weigh solids is to add an excess to the
| scale and then *remove* the material until you reach the desired
| weight.

I must disagree with that, it is absolutely forbidden in Chemistry because
there putting anything back in the jar may cause contamination. In
cooking it must be a bad thing.

Dave F

"rmp" > wrote in message >.. .
> Usually strain gaged loadcells have very small deflections. So movement
> sticking is unlikely to be an issue.
>
> Software issue may relate to low cost analog to digital conversion, reading
> frequency, etc.
>
The deflection doesn't have to be large for friction to be a factor
and anyway the deflection on *my* digital scale is large enough to be
visible. If you go back and look at the data from the original
poster's experiment, the only real "mystery" here is why the results
are different between adding weight quickly and very slowly. The
easiest (and therefore most likely, IMO) way to explain that result
is, as Dave has said a number of different ways, by the effects of
friction: there is something "sticky", if you like, in the mechanism
between bowl and strain gauge; that stickiness is overcome if you add
(or withdraw) weight quickly but not if you sneak it on slowly. Any
other explanation is a stretch. The other possibilities that have
been mentioned - software, strain gauge/gage, a/d conversion, and so
on, are unlikely to vary with time. In other words, I'm with Dave.

- Mark W.

Mark Willstatter wrote:
>The other possibilities that have
> been mentioned - software, strain gauge/gage, a/d conversion, and so
> on, are unlikely to vary with time. In other words, I'm with Dave.

But the removal and replacement of the bowl (a large sudden change,
which should overcome any inherent "stickiness") clearly demonstrates
that the bowl has "lost weight". i.e. the scales have changed their
concept of the "zero point".

It would be interested to see if the experiment could be repeated a
number of times until the weight of the bowl registered "zero".

Based on the evidence to date, I could well believe that the scales are
adjusting their "zero point" over time.

Dave W.

David Wilkinson > wrote:

>But the removal and replacement of the bowl (a large sudden change,
>which should overcome any inherent "stickiness") clearly demonstrates
>that the bowl has "lost weight". i.e. the scales have changed their
>concept of the "zero point".
>
>It would be interested to see if the experiment could be repeated a
>number of times until the weight of the bowl registered "zero".
>
>Based on the evidence to date, I could well believe that the scales are
>adjusting their "zero point" over time.

Yes indeed. But if anybody's still doubting, look at this:

1. Weigh a spoon, a cup, and a bowl in turn - 30g, 194g, and 274g.

2. Slowly add 20g of powder to bowl and take combined weight - 278g.
16g lost this time.

3. Without zeroing, weigh spoon, cup, and bowl again - 14g, 176g, 258g.
Each is 16g or 18g lower (the scale increments in 2g steps).

So the zero point has shifted by about -17g.

--
Farry

Mark Thorson > wrote in :

> Adrian Tupper wrote:
>
>> Not according to the OP. And just how accurate does one need
>> to be? All the recipes I know have quantities given in whole oz
>> or sometimes half-oz. My scales are accurate enough for that.
>
> Maybe he's using the scale to weigh illegal drugs,
> in which case he certainly might care about fractions
> of an ounce. He couldn't just say that's what he's doing
> in a Usenet newsgroup.

Ah. A sensible explanation!

--
Adrian

Dave Fawthrop > wrote in
:

> On 27 Jan 2004 08:54:22 -0800, (-L.) wrote:
>
>| Farry > wrote in message
>| >. ..
>| > Hi.
>| >
>| > If anyone's considering buying one of those expensive Salter
>| > Electronic Kitchen Scales, you'll probably want to be aware of a
>| > design problem that messes up the accuracy. You can work around the
>| > problem, and still get accurate readings, but it is a rather daft
>| > fault. This is what I've put on Salter's feedback form, and I'm
>| > waiting for their reply:
>| <snip>
>|
>| Just FYI. The proper way to weigh solids is to add an excess to the
>| scale and then *remove* the material until you reach the desired
>| weight.
>
> I must disagree with that, it is absolutely forbidden in Chemistry
> because there putting anything back in the jar may cause
> contamination. In cooking it must be a bad thing.

Nearly everything weighed in this manner is dry and I wouldn't hesitate
putting sugar, raisins or even butter back in the packet.

--
Adrian

Quoting from message >
posted on 27 Jan 2004 by Adrian Tupper
I would like to add:

> Mark Thorson > wrote in :
>
> > Adrian Tupper wrote:
> >
> >> Not according to the OP. And just how accurate does one need
> >> to be? All the recipes I know have quantities given in whole oz
> >> or sometimes half-oz. My scales are accurate enough for that.
> >
> > Maybe he's using the scale to weigh illegal drugs,
> > in which case he certainly might care about fractions
> > of an ounce. He couldn't just say that's what he's doing
> > in a Usenet newsgroup.
>
> Ah. A sensible explanation!
>

There's an electronic scales for re-loading ammunition, weighing powder,
calibrated in grains - can't work that out in grammes/ounces at this time
of night.

--
....ElaineJ... Home Pages and FAQ of uk.food+drink.indian can be viewed at
....Kinetic... http://www.users.zetnet.co.uk/ejones/ufdi/index.html
...StrongArm.. Under construction, FAQ, recipes, tips, booklist, links
....RISC PC... Questions and suggestions please, email or to the newsgroup

>>> Not according to the OP. And just how accurate does one need
>>> to be? All the recipes I know have quantities given in whole oz
>>> or sometimes half-oz. My scales are accurate enough for that.
>>
>> Maybe he's using the scale to weigh illegal drugs,
>> in which case he certainly might care about fractions
>> of an ounce. He couldn't just say that's what he's doing
>> in a Usenet newsgroup.

Some of us use our scales to weigh pool cues and shafts, in 1g or 1/10
oz. increments. 8

-- Larry

Dave Fawthrop > wrote in message >. ..
> On 27 Jan 2004 08:54:22 -0800, (-L.) wrote:
>
> | Farry > wrote in message >. ..
> | > Hi.
> | >
> | > If anyone's considering buying one of those expensive Salter Electronic
> | > Kitchen Scales, you'll probably want to be aware of a design problem
> | > that messes up the accuracy. You can work around the problem, and still
> | > get accurate readings, but it is a rather daft fault. This is what I've
> | > put on Salter's feedback form, and I'm waiting for their reply:
> | <snip>
> |
> | Just FYI. The proper way to weigh solids is to add an excess to the
> | scale and then *remove* the material until you reach the desired
> | weight.
>
> I must disagree with that, it is absolutely forbidden in Chemistry because
> there putting anything back in the jar may cause contamination. In
> cooking it must be a bad thing.
>
> Dave F


Actually it is the recommended method by most makers of analytical
balances. That's how they are calibrated.

-L.