Recommendations For A Parts Counting Scale - Page 1
Forum section: electronics / general

author: Farley
author_rank: Regular Contributor
timestamp: March 24, 2016, 12:44:02 pm
content: After searching Amazon I've noticed that parts counting scales range in price from under $50 USD to several hundred dollars. If anyone has experience with any particular model I'd be interested in hearing opinions or recommendations.The scale I need will be used for inventory counting of electronic components such as thru-hole resistors/capacitors/etc, probably some SMD parts, and small hardware such as M2-M4 machine screws and similar hardware.

author: elecman14
author_rank: Unknown
timestamp: March 24, 2016, 02:04:58 pm
content: While this is not a recommendation for a specific scale it is a general observation. In my neck of the woods the local scale calibration outfit actually rents scales. They show up a few days before the plant inventory and are calibrated. The bean counters claim that this saves money. You might also want to check with your local calibration outfit (if you ever think you will need to get them calibrated or verified). They may have a scale that is easy to work on. I generally will ask their opinion before buying equipment. It helps build a good working relationship with them and they are happy when they get equipment that they are familiar with or is easy to work on.

author: SeanB
author_rank: Super Contributor
timestamp: March 25, 2016, 11:47:34 am
content: While I will not give you any recommendations I will give you a few pointers to look for. First get an idea of the mass of the lightest part, and remember that. Then the heaviest box of that part, and the largest mass box you will be using as a count, along with the mass of a single item.This gives you now a few things, the lightest item is the limit, the scale resolution must be smaller than this, or you will get count errors which grow as the mass of the item approaches the least significant digit. Ideally you want 5 counts per unit of smallest mass, so you only will have errors in counting packs over 200 parts. That way you can count bags and see easily if they are all correct, at least for bags which are identical in size and mass, and which have the same labels on them. The maximum mass the massmeter can read limits you in the number you can count at a time, and remember that the Tare mass eats away at this limit.Thus you likely will need at least 2 massmeters, one with a resolution of around 50mg, and probably with a maximum mass capacity of 1kg. That will do small resistors with reasonable accuracy. The second one will probably be a counting scale with 0.5g resolution, and with a 30kg maximum load. This will work for parts like screws and nuts, handling parts larger than M6 (1/4in) up to M20 with ease.When using the massmeters use metric settings, using ounces will lead to tears in trying to fit the resolution of the massmeters into neat blocks. milligrams are a whole lot easier to use than trying to count where your count starts in grains, then changes to carats, then changes to ounces and quarter ounces then swaps to pounds and ounces, each with it's own rounding errors.

author: KL27x
author_rank: Super Contributor
timestamp: March 29, 2016, 03:16:57 am
content: QuoteI've gone through a few different cheap-o electric scales for this type of task. This one is the best-to-date, because the weight is displayed very quickly.I don't put a lot of faith into a more expensive unit. I think it you drop any of these scales from a significant height, you are going to be out of luck.

author: Farley
author_rank: Regular Contributor
timestamp: March 29, 2016, 06:17:02 pm
content: Thanks to all for the information. I'll probably choose an inexpensive one similar to the one KL27x provided the link for. At that price if it doesn't work out for me it's not a big issue.I am still interested in hearing of any personal experiences with specific parts counting scales, good or bad.

author: xyrtek
author_rank: Regular Contributor
timestamp: March 31, 2016, 05:42:51 pm
content: If I were to pick one scale to use for parts inventory I would probably aim to get one with at least one interface that can be used to automate the process.Depending in how much time you are planning on spending doing inventory this could be a great suggestion or useless hehe.

author: ChunkyPastaSauce
author_rank: Unknown
timestamp: April 06, 2016, 03:10:51 am
content: I recommend buying used. Good scales are usually not cheap new. You can get laboratory grade scale fairly cheaply if you have time too keep youre eyes open.Have one of thesehttp://www.geminibv.nl/labware/mettler-ae200-balance. Pretty sure it will count the smallest smd parts you can think of - 0.1mgreading. Picked it up for $50.I also have one ofhttp://www.handelskontor-freitag.de/Verkauft/Waage-Sartorius-LC-4200-0D2--4200g-d-0-1g-e-0-5g--eichfaehig.htmlGood for large parts, but will not count small parts -0.1greading. Picked up for $35.Both have dataports.Both of those scales would be considerably more if buying new.I saw a number of 1mg scales on amazon for under $50. They are cheap, so might be worth a shot to give one a try, but I wouldn't ordered it expecting it to work out. Also at 1mg, if it doesn't have a draft cover then throw it out because it's almost certainly crap.

author: Farley
author_rank: Regular Contributor
timestamp: April 07, 2016, 09:23:57 pm
content: I ordered one of these yesterday and received it today:http://www.amazon.com/Etekcity-Digital-Kitchen-Stainless-Resolution/dp/B00QFCG5ZQ/ref=sr_1_5?ie=UTF8&qid=1460062717&sr=8-5&keywords=parts+counting+scale+.001Today's price of $14.99 USD is $2 cheaper than I paid for it yesterday. The word "Kitchen" in the description didn't fill me with confidence.I used it to count some 1/4W resistors. It counted 100 correctly. I haven't tested any larger quantities. The minimum required sample size for counting is 25 pieces which is quite a few. I think the more expensive scales can use a smaller sample size. It also allows for the weight of a bin or tray to be zeroed out.

author: ChunkyPastaSauce
author_rank: Unknown
timestamp: April 07, 2016, 10:24:58 pm
content: Quote from: Farley on April 07, 2016, 09:23:57 pm.01g accuracy scale should count 1/4watt through hole resistors fine, assuming the scale is accurate. One 1/4 watt thru hole resistor typically weighs about .135g, so .01g scale is order of magnitude more accurate, which is what you need.... pretty awesome for $15 bucks. My 0.1g scale would likely have problems I think. Small SMD parts on .01g scale might not work out though.Quote from: Farley on April 07, 2016, 09:23:57 pmPart of the reason for the 25 initial count is to get the true mean weight, assuming normal distribution. If you grab 1 random part as the reference weight, its probably not the true mean; the error accumulates the more parts you're trying to count. So even if you had a .00001g accurate scale, you'd likely still have to weigh an average

author: JuKu
author_rank: Frequent Contributor
timestamp: April 15, 2016, 11:09:06 am
content: Too late for you, but here are my observations. I have a Kern counting scale, which I'm satisfied of, but with my experience with it, I might choose another model now:- 0.1g is too coarse for electronics, imo. As noted, you want several counts resolution, the more the better. My scale has 0.01g resolution, and it is still not enough for smallest parts I use. I can happily live with that, as I use the scale for mechanical parts. For example, a M3 washer weights about 0.07g. I have no issue bagging some extra, as they cost 0.0x cents each. But electronics parts with similar size can cost several €/$'s.- You really want a display for count and the ability to zero out a container. It is time saving to be able to put in a known count; fixed 25 pieces sounds like a lot. It might be ok though, I haven't tried. If I need a reference for 50, I put in ten, pour in 50 and set it again.- Calibration weights are (very) expensive, but you don't need calibration nor absolute accuracy for parts count. You don't care if your scale says the part weights 1.000g but in reality it weights 1.003g. However, you do want to know that when your scale measures 234g and shows 234 pieces, there really are 234 pieces. In other words, you want very good linearity.- My scale has memory function, I can put in 30 parts and their reference weights. However, without a computer or computer-like interface, that is more hassle than it is worth. Besides, the scale drifts. If I weighted a part a few months back, today it might be off for one piece per 50. I don't know if the scale drifts or if the environment (like air pressure) changes cause that. These together cause me to count ten pieces before starting weighting. Does not really add up, as I fill few ten bags per part at a time. I don't miss the memories.- If you plan to use it much, you want to use a low profile scale. Mine is uncomfortable high in relation to the table top where all the other stuff is. I don't want to use it the whole day.