Cheap scale test - part 1 repeatability

[JimSC]

Cheap scale test part 1



I saw some positive remarks recently regarding a cheap Amazon Chinese milligram scale the other day and thought what the heck and bought one.



To be exact I ordered the Smart Weigh GEM20 High Precision Digital Milligram Scale 20 x 0.001g Reloading, Jewelry and Gems Scale



https://www.amazon.com/dp/B00ESHDGOI/?tag=accuratescom-20



I see so many scale discussions on these forums and not everyone can afford nor do they need a thousand dollar lab balance so I decided to see how well a $20 dollar scale could perform on a reloading bench



It is a small scale and battery only, no port for an AC adapter. It comes with 2 cheap AAA's which will probably die at a young age. Just something to be aware of if you decide to purchase one. Luckily due to my addiction to toy drones I have a good supply of rechargeables. If you have minimal electronic skills it would be easy to wire in a 3V power supply socket



It comes with a pair of tweezers and a pair of 10g check weights. There is a small pan included which would be good for pistol loads but if you are loading a 300 Win mag bring your own pan. The draft shield is hinged and with it closed there is only about 3/8 inch clearance. Sufficient for the provided pan but your average reloading pan just ain't gonna fit.



The unit has a automatic shutoff after one minute of non use which is a both blessing and a curse. It is impossible to burn out a set of batteries when you get distracted and also impossible to warm up the electronics. I figured out a work a round by placing and removing a bullet on it randomly while watching a cat video on Youtube for 5 minutes. Warning the unit is slow to settle. Using the grain setting you have 2 digit resolution. For 10 or 15 seconds the scale will vary .02 up and down before settling.



Nothing too scientific here but I want to test the scale for :

1. repeatablity when weighing bullets
   
   
2. sensitivity when trickling powder
   
   
3. comparing comparing various weight loads against the beam
   
   
4. the last test will be shooting three ten round groups at 100 yards over a chrono
   
   10 loaded using the Gem20 thrown and trickled to weight
   
   10 rounds loaded with my RCBS Chargemaster
   
   10 rounds loaded on my beam and trickled to weight

The unit seems fairly sensitive to air currents so both the ceiling fan and the AC will be turned off during all tests and the unit will be placed on a leveled paving brick for any possible vibration



For part one of this test I picked out three Berger 80 grain VLD's, three Nosler 123 grain CC's, and three 142 grain Sierra Match Kings. I weighed each bullet 5 times to check the repeatability of the scale. I used three bullets I had on my shelf. I measured in grains with two digit resolution, to be more precise I could have used milligrams but how much resolution do you need if you are weighing bullets? When I do the powder related tests I will convert the grains to grams to get three digit resolution.

Keep in mind this is not a test of the bullets, three bullets is not a wide enough sample to make any sort of judgement. I could have weighed one bullet of each box 15 times for the purpose of this test. Here are the results.

 

[Depart123]

That is right in line with what I've seen with mine. When well calibrated, it is +/- .02 grains. I use both the negative weight value of the pan when taken off, as well as the 10g check weight I place on it to keep it active to keep an eye on the calibration. I usually have to re-calibrate it about once every 50 rounds or so, but it only takes a few seconds to do that.

 

[Dusty Stevens]

Cat videos. Check the cucumber ones out

 

[Falfan2017]

I'd be interested in seeing a test of this.
https://www.amazon.com/dp/B076D6N4S2/?tag=accuratescom-20

Similar specs to an entry level sartorius but less than a third the price.

 

[Peebles24]

Noticed on your test every third had the highest ES at .04gr. Wonder if that is a coincidence or if that trend would continue.

 

[JimSC]

Noticed on your test every third had the highest ES at .04gr. Wonder if that is a coincidence or if that trend would continue.

Good observation, my first instinct is twice is a coincidence three times could be a trend. It is something to watch.

I don't weigh bullets normally and would be interested in the opinions of those who do. Other than the slowness in settling I think it would be perfectly adequate for weighing bullets or determining case volumes.

I have errands this morning but this afternoon I want to see if it is good enough to use for trickling. I was very satisfied with it's performance in the repeatability test.

I'd be interested in seeing a test of this.
https://www.amazon.com/dp/B076D6N4S2/?tag=accuratescom-20

Similar specs to an entry level sartorius but less than a third the price.

if you want to send me one I will be happy to test it

on the serious side one of the reasons I am running this test is to see how the less expensive scales perform. If the $20 one tests well I may buy one a few steps up with a AC option and hopefully a bit faster settling time.

 

[powderbrake]

a comment on the results:
If the weight is unchanged, the repeatability of the scale is the sum of it's accuracy and drift. The manual on this scale has no accuracy or repeatability or drift specifications, just a "readability" of .02 grains, which I suspect is actually resolution.

The data shows it measured the bullet #2 at 123.12 and 123.02, therefore any reading of anything could be within a range of .10 with this scale. AVE and ES mean nothing in this case, you are concerned that each reading is correct. You don't "average" out powder drops, each drop is expected to be accurate, as each shot is scored independently.

I am not knocking this scale, I am just bringing out the point that each reading must stand alone, and the extremes of the span of the readings of the same weight is the limit of repeatability of this scale.

 

[JimSC]

a comment on the results:
If the weight is unchanged, the repeatability of the scale is the sum of it's accuracy and drift. The manual on this scale has no accuracy or repeatability or drift specifications, just a "readability" of .02 grains, which I suspect is actually resolution.

The data shows it measured the bullet #2 at 123.12 and 123.02, therefore any reading of anything could be within a range of .10 with this scale. AVE and ES mean nothing in this case, you are concerned that each reading is correct. You don't "average" out powder drops, each drop is expected to be accurate, as each shot is scored independently.

I am not knocking this scale, I am just bringing out the point that each reading must stand alone, and the extremes of the span of the readings of the same weight is the limit of repeatability of this scale.

excellent points and I agree. The lowest resolution on this scale when in grain mode is .01 grains. Last night what I was seeing was a drift of plus or minus .02 grains. Using a target of 5.0 gns the typical was anywhere between 4.98 and 5.02 add in a error of .01 and that grows to 4.97 to 5.03. Correct me if I am wrong here, I have a thick skin and am here to learn and share. Most low to mid end scales only accurate to plus or minus one of their lowest resolution. By resolution I mean the number of digits to the right of the decimal point. For example any typical starter reloading scale that only reads down to .1 gn a reading the weight of a 5.0 gns charge could be anywhere from 4.9 to 5.1 gns, if I am understanding this correctly

Here is a confession. This scale will never be my main reloading scale, it's main purpose was to see how consistent my modified beam is. It's secondary purpose is if I ever decide I want to measure case volume again I have something a bit better than my Rangemaster. For a couple of months now I have been thinking about going the A&D or Sartorius route and that option is still open. However my first impression this morning doing some powder measurement comparisons left me with the feeling that I am getting within 1 or 2 kernels of Varget with the beam. Jury is still out to lunch on whether that much difference will show up over the noise of my shooting technique. My wind and mirage skills sucketh mightily but my vertical spreads are very acceptable

I did the first half of the next test earlier and used gram mode which goes out to three digits to get a bit more resolution. That was loads trickled on the beam then checked against the electronic. When I measure some loads trickled on the electronic and checked against the beam I will post it

 

[powderbrake]

JimSC;
You are correct in saying that with a reading of 5.0, it could be anywhere between 4.9 to 5.1.

A scale is just so accurate. You cannot make it more accurate by changing scales. Yes there is more resolution (.001) on the gram scale than the (.02) on the grain scale, but it is on a larger weight. The accuracy is UNCHANGED. The additional resolution is essentially not an advantage because the ratio of the gram/grain is figured into the resolution display.

Comparing one scale to another is, in general, a waste of time. Without calibrated weights, there is no way for a person to know what the true reading is. You simply have to trust the readings on the scale, and to buy a scale that is within the accuracy you desire.

As an example, do you trust your ruler, or your measuring tape, or your yardstick?
If you lay 2 or 3 rulers on the table, side by side and "compare" them, which one is correct? They probably don't read the same. You cannot say which is correct without a method to measure the absolute accuracy of each.

A reference weight, like a bullet you keep (clean and in a clean container) that you know the "reading"(weight), can be used as a rough reference that the scale is still close on calibration. A better choice is frequent calibration with a calibration weight.
If you really want to calibrate to a scale's accuracy of .001 g, you need a calibration weight more accurate than that. A 100g +- .0005 calibration weight is about $77.

For reloading purposes, it is not necessary to test or calibrate a scale to it's level of accuracy. It is necessary to calibrate, but you can do so with a calibration weight that is not better than its precision. A 100 gram weight that is within .016 gram will work. ($8) It will calibrate the 100 gram point to within .016 gram of absolute accuracy at 100 grams of weight. So if you weigh something and it says it is 100grams, it could be 100.016 grams, 16/100,000 off, but who cares? It will give the same readings on the same weight within it's resolution.

I use mine mostly for powder weighing, and at 1.9457 grams (30 grains), the calibration error of absolute weight is 1.9457/100 X .016 = .0003 grains (.048 grains) but you cannot see it.

 

[nmkid]

I'd be interested in seeing a test of this.
https://www.amazon.com/dp/B076D6N4S2/?tag=accuratescom-20

Similar specs to an entry level sartorius but less than a third the price.

Couldn't find any reviews on it.

 

[Ares]

Powderbrake is pretty much right about his post.
And the extra resolution of the scale gives you nothing in terms of accuracy and repeatability.
Also the test weight you get with it is probably not very accurate to begin with.
As stated a certified test weight at least twice as accurate (preferrably more) as the scale itself should be used, but simply for reloading purposes what you need is a reference that is repeatable more then anything. If the actual weight of your charge is 0.1 grains above or below the actual vaule is not really important, as you develop the load yourself.

As for the weight linked in Amazon its some kind of chinese analytical balance. and it does'nt read out in grains if that matter to you.
And it does not state the manufacturer/brand of the weight witch is usually not the best sign.

There's also plenty of other good suppliers for analytical scales, not only Sartorius and A&D. Ohaus and Mettler Toledo fx is generally of very good quality too amongst others.

 

[Ned Ludd]

The least expensive MFR balance that will weigh to 0.1 mg readability and comes from a reputable manufacturer is the Sartorius Entris 64-1S, which can be purchased for around $1K. A comparable Ohaus will balance cost about the same, perhaps just a wee bit more. Mettler Toledo balances are the Cadillacs of precision weighing, similar features will cost you at least twice as much.

I would also be curious to know how the BSM-1204 balance listed/linked above functions. I tried to find a link to its manual and tech specs, but couldn't. Until such time as more review information is available from actual users, its reliability and the origin of its design remain questionable, regardless of the low cost.

 

[JimSC]

JimSC;
Y

Comparing one scale to another is, in general, a waste of time. Without calibrated weights, there is no way for a person to know what the true reading is.

My next statement is going to cause some to have a heart attack. I really don't care what the true weight is I just want the scale to be as precise as possible.

On this post I weighed three of the same bullet 5 times using the grain mode which only has a resolution of 2 places (1/100th). I did this with 3 different weight bullets for a total of 45 weighing's. The largest spread on any bullet weighed was .04 grains. If I can load 45 rounds and the powder charges are all within .04 gns of each other that hits the good enough factor bell for me

While I have no argument about part of your post it complaining about my accuracy testing or lack of it you need to understand that it is the precision of a scale that matters when reloading. I could care less if a load is 41.450 or 41.490 as long as all of 100 of the loads are somewhere between 41.45 and 41.49.

The scale also passed comparison with my modified beam in test 2 which is 100% repeatable. Gravity does not need to warm up nor does it change

in test three I weighed several bullets individually and then started combining them . Up to about 250 grains total weight the scale did well, after 250 not so well

This scale has a lot of warts and flaws but it's precision, at least when new, is not one of them. For someone who only wants a scale to set a powder throw or weigh 100 bullets or do 100 case volumes this will get the job done for $20 bucks. It is not a lab balance by any stretch of the imagination but the question is do I need a lab balance.

If I were looking for a workhorse electronic for day to day weighing I would take about $200 to $300 and get a low end A&D or a Tree Brand. At one point I considered going all in on a auto throw complete with a Sartorius Luckily I am not a impulse buyer. With consistent SD's in the single digits with my beam and a average load time of 1 min per round seated that hits the good enough mark for me. For setting my powder throw or weighing cases and bullets this little el cheapo is all I need

Now when they make a scale will raise my wind mirage IQ up 100 points I will buy one and pay for overnight shipping

 

[powderbrake]

My next statement is going to cause some to have a heart attack. I really don't care what the true weight is I just want the scale to be as precise as possible.

I completely agree with you.

And I did not intend to fault any of your testing, it has been rigorous and well documented.

 

[WindSurgeon]

I gave up on digital scales. I just could not trust the ones I bought or borrowed to try, and refuse to spend a grand on a lab quality scale. They also seem to slow down the reloading process, and once I lost confidence in their repeatability, was doubling my loading time as I was constantly re-calibrating them and checking weight. Wish it would work due to the resolution.

 

[Davey Boy]

What I did was, took all my calibration weights to 3 different pharmacies and noted their weights. All 3 were the same. I marked down what the pharmacies came up with and recorded each weight. I have 4 1gram, 1 5gram, and 1 10gram. The 4 1gram weights had 2 weights to them .1 grain apart, and the 5 and 10 gram were within the weights I load. Much easier to see how far the electronic scale is off. Chargemaster not at all off. Now that I have had my calibration weights calibrated as such, its simple.

I figure that pharmacies have better scales than most of us, so take your favorite weight or bullet and have them weight it, then record and keep it clean.
Just my 2 cents.

 

[pirate ammo]

Anyone who takes the time to play around with stuff and write a review should be thanked for their efforts, right or wrong. They have went a lot farther then some have done.
edit: Jim, you do a better job than I do..

 

[Twoboxer]

It’s well known that the big problem with “cheap” digital scales is that they respond to noise causing a change in readings. So otherwise properly functioning digital scales that appear to work well in your reloading room may not work well in someone else’s. In today’s “everything connected” electronic age, the likelihood they will not work well grows every day.

Case in point – my 6th scale was a GemPro 250. In addition to not responding to a single kernel of added powder, it displayed the same behaviors as my truly cheapo Hornady, as well as the Pact and Chargemaster dispenser/scales that came next. Fluttering, loss of zero, inconsistent weight readings for the same item, etc.

Every time I re-zeroed the Gempro (and the other digitals), I wondered exactly when it had “lost zero”. On its way up to the powder charge weight? Or on the way down below (or to) zero?

So I gave the GemPro to my buddy who owns a flip phone and reloads in his “unconnected’, detached-garage man-cave. He’s quite happy with it, and it’s probably more repeatable for him than his earlier use of various balance beam scales. In any case, he uses quality but still factory rifles and is looking for “minute-of-deer” at <=300yds.

It’s equally well known that the A&D FX120i (and others) do NOT respond to noise. Once I bought mine, I used my Chargemaster to throw close-but-low, and manually trickled up on the A&D. In doing more than 1,000 reloads that way I saw each and every Chargemaster throw weight and how it varied from the programmed target. The clear conclusion: the Chargemaster (like the GemPro) was USELESS to ME, in MY reloading room, especially when throwing groups of load development charges 0.3-0.5gr apart.

TLDR: Since it is well known that “cheap” digital scales respond to noise, tests in your reloading room (or mine) are not a reliable indication of performance in other rooms.

Personally, I would never recommend a scale less capable than the A&D FX120i to someone else without making them aware of the possibilities. I would not want them to go through 7 scales, like I did, based on opinions, recommendations, and even tests done in someone else’s reloading room.

 

[JimSC]

I have had several electronic scales in this room. My first electronic was a RCBS Rangemaster 750, I had no noise problems with it, my son in law has it now. Then came a RCBS Chargemaster 750, once again no noise issues. The little Smartwiegh Gem 20 is battery powered by 2 AAA batteries so line noise is not a problem and the overhead florescent light don't seem to bother it either. For the record I have had a set of Duracells in it for 4 months now and they are hanging in there. The scale has been remarkably consistent considering it is in a room in a unheated garage, there is a refrigerator and a chest freezer and the garage is fully insulated and has AC but only a space heater for heat. The temps got down into the mid 50's a month or so back, I would use the space heater to warm it but overnight it would get pretty chilly. The RCBS CM worked perfectly fine as did the Smartweigh but a Tree KHR 123 I own went spastic every time the temps changed a degree or two. I finally gave up on re calibrating it every 30 minutes and went back to the Smartweigh and my balance beam until I ordered the A&D last week. The kicker is so far the Smartweigh performs every bit as good as my new A&D. Readings are spot on consistent with each other. The Tree KHR 123 cost almost $250 is worthless unless you are in a climate controlled room above 65F. A friend of my daughters is into dietary supplements so I will probably give it to her

So in answer to the above poster while I do realize that some scales are affected by line noise and florescent lighting , the Smartweigh Gem 20 is not. For $25 to $30 dollars in my opinion this is hands down an excellent little scale

 

[T-shooter]

I went through several scales before before I gave up and bought an FX.

I came to the conclusion to be accurate you need a magnetic force restoration type. The A&N FX-300 weighs the exact same every time (with careful use) and I haven't had to recalibrate it it a couple years. I do have a couple test weights close to my loads and I always check every few weighings. I had to get a Tripp-lite 1200 line filter to get it to work properly. The worst of the bunch was a Veritas 63 (Driftomatic). It was less reliable than the $10-$30 cheapies and cost $300. The best lower cost was the GemPro-300. I had 2 different ones to try. The test below I used 2 slightly different weights and used a few different methods. In each case the numbers never varies over +/- .02 grain. Altogether 250 separate weighings. The weights had to be put on the plate very easy or it would skew the reading. Most hit the middle number. In another test I weighed the same weight 100 times and 1 time it varied .04g,the other time it was +/- .02g. To trickle and get an accurate reading with this scale, it's best to pull and reset the pan on the weighing platform each time.

The large US Solid scientific balance read to the next digit. It was a cheap one, about $300. Couldn't be calibrated in grains, only grams. Very touchy to use and each time the breeze shield had to be closed and let it stabilize. The average accuracy was about +/1 .01g but it would take forever to load anything with this so it was sent back.