Kitchen scale - Page 1
Forum section: electronics / general

author: ipman
author_rank: Regular Contributor
timestamp: July 04, 2011, 05:01:27 pm
content: My mother complained about her kitchen scale not weighting anymore.Of course, it was "take it apart" time.Altough I did know that this scale was refurbished before was sold, what I found inside was beyond my imagination. A double sided PCB soldered only on one side, there were cold solder joints everywhere, some of them had even 80ohms!This is a Laica scale, italian brand, but i doubt that this was manufactured anywhere in Europe.I've photographed only the PCB, which was the worst, but the screws were not tight, some broken, a really nasty job ... I wonder how this ever worked.

author: ndictu
author_rank: Regular Contributor
timestamp: July 04, 2011, 06:06:43 pm
content: Hahaha, that's is amazing. Did you manage to fix it?Also, why are the components on the wrong side, doesn't it fit the right way or what? The resistors should if that little DIP does, maybe the caps are too big? Or maybe they just didn't understand how to put it on?

author: norEL
author_rank: Contributor
timestamp: July 04, 2011, 08:28:34 pm
content: This looks really bad!!Think I can say that I did a better work the first time I tried a soldering iron than the person that have done this "job". haha..

author: Kibi
author_rank: Unknown
timestamp: July 04, 2011, 08:41:05 pm
content: I am lost for words. Simply amazing!

author: ipman
author_rank: Regular Contributor
timestamp: July 05, 2011, 05:02:25 am
content: Yes, i fixed it. The white and green wire had cold joints, around 80ohm each.Of course, i cleaned the old solder on most joints and this time soldered them as they should be.I cannot find the reason why they put the components like this. There was not enough room to fit the caps upright, but there was plenty to fit them to correct side.All components were measured and they were inside the tolerances, even caps had they ESR in normal range. I did not expect that.

author: EEVblog
author_rank: Unknown
timestamp: July 05, 2011, 09:37:07 am
content: What a shocker!Dave.

author: saturation
author_rank: Super Contributor
timestamp: July 05, 2011, 02:21:48 pm
content: Wow, one of the worst I've seen, much worse than anything I've bought. Doesn't it have a 'made in' anywhere?Battery operated scales are far more prolific today, but old style analog weight based scales or even spring scales are accurate enough for most anything a consumer uses. The only time I've seen electronics truly be of value is replacing a Mettler quality balance, because precision weights are very expensive, making an electronic version not only is cost effective, made correctly its superior due to near zero maintenance beyond calibration.

author: ipman
author_rank: Regular Contributor
timestamp: July 05, 2011, 04:02:02 pm
content: No, there is no indication about where it was manufacured. But as usual I suspect a country whose name starts with C and end with AIt's usefull because it can measure grams. Yeast in a home-made bread must be between 3 and 7 grams, so it's more usefull than analog scales which cannot measure with such resolution. Compared to another similar scale, indications are the same and the bread made accordingly is soooo ... good.

author: Zero999
author_rank: Super Contributor
timestamp: July 05, 2011, 04:27:41 pm
content: How do you know if it's accurate?It may be a couple of grams out.Here's how I'd test it. take an empty syringe, put it on the scales and set them to zero. Fill the syringe with a known quantity of water and weight it again. 1ml of water weighs exactly 1g at room temperature and atmospheric pressure and a medical grade syringe should be more than accurate enough for what you need.

author: Semantics
author_rank: Contributor
timestamp: July 05, 2011, 04:31:25 pm
content: Quote from: ipman on July 05, 2011, 04:02:02 pmTsk tsk, Canada.I'm guilty of picking up stuff from Deal Extreme and it's always scary to open it up and see the craftsmanship. That some of these things even work at all I pretty much call it all a miracle. Gotta hand it to China, though, that they're pushing the limits of non-manufacturability. I find it fascinating how badly things can be built, ignoring any IPC class of work, and still sort of function.

author: sacherjj
author_rank: Frequent Contributor
timestamp: July 05, 2011, 04:33:37 pm
content: Quote from: saturation on July 05, 2011, 02:21:48 pmKitchen scales don't need to be terribly accurate, but they must be electronic. Once you have switched to cooking by weight instead of by measure, you life gets very easy. The secret is because of the Zero tare, this is really hard with non-digital scales.Put bowl on scale. Zero tare.Add first ingredient, until weight is correct. Zero tare.Add second ingredient, until weight is correct. Zero tare.etc, until done. Mix.This makes cooking SO much faster and you don't mess up all those measuring cups. This is the reason I have 2 digital scales for the kitchen. (But I'm the odd husband who loves cooking and might want to be a chef if the pay was any where near what I make as a programmer.)

author: ipman
author_rank: Regular Contributor
timestamp: July 05, 2011, 04:41:03 pm
content: Cooking for engineer needs digital scales. Numbers are everything, I recon.I understood breadmaking by numbers and ratios. Guaranteed to work, and results are quite consistent.@Hero99: yes, the scale has an error more than 1 gram at 3 grams measured. But still, you cannot measure that resolution with a (quite cheap) analog scale. And, afther that, tare function cannot be beaten.@Semantics: ok, I forgot about Canada. But I doubt they have such industry. A Canadian made scale under an Italian brand sold cheap in Romania? Very unlikely.

author: Zero999
author_rank: Super Contributor
timestamp: July 05, 2011, 05:09:02 pm
content: Do you know what sort of accuracy are you getting? Have you tested it?

author: ipman
author_rank: Regular Contributor
timestamp: July 05, 2011, 06:54:36 pm
content: Sort of.I've put on it the content of a yeast bag, weighted by the producers. They claimed 7 grams, the scale read 7 grams. I am fine with that, I don't need sub-gram precision, even a 1-2 gram accuracy is good enough, will not make much difference in bread-making.

author: Neilm
author_rank: Super Contributor
timestamp: July 05, 2011, 07:05:16 pm
content: Quote from: ipman on July 05, 2011, 04:02:02 pmShame - we could have sent them a link to EEVBlog #183Neil

author: saturation
author_rank: Super Contributor
timestamp: July 06, 2011, 09:48:11 am
content: Tare makes sense that way, an engineer minded person can easily choose a proper scale too, with resolution and accuracy to fit the need. Clearly, chemistry is nearly all in weights.I was thinking more of its use in dieters and diabetics, were weight = calories, but making easily reproducible meals has its appeal.

author: Zero999
author_rank: Super Contributor
timestamp: July 06, 2011, 05:47:39 pm
content: Quote from: ipman on July 05, 2011, 06:54:36 pmThat's amazing given the poor build quality, perhaps they haven't skimped on the strain gauge, just on the assembly?

author: ipman
author_rank: Regular Contributor
timestamp: July 06, 2011, 08:14:39 pm
content: Strain gauge is for sure produced as a whole by others. It is sealed, wires are stuck with some goo, looks like a decent quality. It works just fine. (Sorry, no pictures).I did not had access to weight standards, so I improvised weighting things and comparing with their specified weight on package, at the same time comparing with a similar scale and that worked like a charm: both indicated same weight.

author: Unknown
author_rank: Unknown
timestamp: July 06, 2011, 08:27:50 pm
content: Quote from: saturation on July 06, 2011, 09:48:11 amWeight is almost exclusively used for solids in chemistry, i.e. for weighing them just before they're dissolved. Weight also get tricky for small volumes, try using a balance and spoon to add 1ul. Just weighing 1mg gets interesting, any airflow will screw up your measurement. Pouring doesn't work at those volumes, and if you use a temporary container (like weighing paper), 90% of it would stick to the container.For cooking it's different since volumes are large and required accuracy is low.

author: saturation
author_rank: Super Contributor
timestamp: July 06, 2011, 10:08:36 pm
content: Yes, clearly chemistry is also in various liquids and gases, but meant just for the purpose of the gross measurements in food. I'm not sure if cooking by the numbers will appeal to chefs, but its a wonder why its not used often if precise repetition is preferred?Quote from: alm on July 06, 2011, 08:27:50 pmFor tiny quantities, analytical techniques appear. A simple one is remeasuring the temporary container for residuals weight after emptying. At that resolution, scales require special mounts and tables to be set near absolute flatness, shock absorbancy and chambered against airflow. Lucikly we don't get so tiny, unless there are gourmet ants!

author: ipman
author_rank: Regular Contributor
timestamp: July 07, 2011, 10:04:40 am
content: I am an engineer, so I understand numbers easier than chef do understand receipes.Even measuring the same weight with allmost-a-gram precision, there are many other factor which will make a food not exactly a clone of the previous one. In breadmaking, flour can differ, temperature is not the same, when you put "a teaspoon of sugar" some crystals can fall and feed better the yeast in one part of the bread, making it inequal, and so on.We, technicians and engineers (politically corect!) call this "tolerance"

author: saturation
author_rank: Super Contributor
timestamp: July 07, 2011, 11:23:33 am
content: Yes, and the materials used, the ingredients, pots, and cooking heat, can have much variability, so precise measurements doesn't guarantee uniformity or the desired outcome, however that's defined. Luckily, processed ingredients rather than raw or fresh material, is more homogenous and works better.Military, fast foods, and cafeteria cooks do it by the numbers or measures, and their cooking has a reputation of its own.Chefs taste and examine the ingredients purchased to insure it has the characteristics they need, if its less or more than expected, they adjust the recipe as needed, most sample the effects of cooking and adjust in the pot too. So in the end, chef style is tied to the chef's palate, and the recipe is a guide not the law.Quote from: ipman on July 07, 2011, 10:04:40 am