Digital scale nightmare.

[Sticks]

Been absent for a while, but still active in my hobby as much as money will allow.

Sitting at home recovering from a rotator cuff repair so i decided to get my stockpile back up and deal with old older mishaps.

Anyhow, I was finishing up food for Roo Roo Becky (6.5 PRC), using 54.14 (yes, to the hundredths - 1 kernel of powder***) of RL26, and my digital scale that I have been using started going schitzo. Jumping around .13gr just sitting there, and my tare weight would wonder around +/- .3gr periodically after pulling the powder tray/funnel to reload. I.E. - Tare weight set at 128.18, then 10 charges later tare would read 128.46.

Now this scale is my verification scale. I am using the Frankford Arsenal Intellidropper to do the automated bulk weigh, then transfer over to my milligram scale to dial in that pesky +/- 5 kernels.

So, I put everything on hold and after re-calibrating several times, and 1 hour of testing I decided to bag it, call the 4 year old Chicom scale dead and ordered some replacements - 3.

I bought the same one again, and two other designs that will run into the hundredths. I took my powder tray, a 123gr pill, and one after the other, weighed them, and logged it with frustrating results.

Twin started at 122.88, and after 11 weighs, ended at 122.74 with a low of 122.72 and high of 122.88. [.16]
Schitzo started 122.9 and ended at 122.86 which was also the low and high, but had 3 episodes of fluctuating +/- .5 grain (1 gr variance). [.04]
Model 1 started at 122.82 and ended 122.77 also the high and low. [.05]
Model 2 started 122.8 and ended 122.82 with a low of 122.76. [.06]

Calibrate and run it again, High and Low.

Twin 122.9 - 122.8. [.1]
Schitzo 122.9 - 122.88 but fluctuated 3 more times. [.02]
Model 1 122.85 - 122.73. [.12]
Model 2 122.82 - 122.75 [.07]

So now I calibrated again, left the scale at zero (BIG revelation here) and ran my powder tray with my 54.14 grains of powder. Empty tray, High - low [diff].

Twin 128.46, 182.6, 182.48 [.12]
Schitzo 128.28, 182.5 - 182.44 [.06] 4 episodes
Model 1 128.37, 182.13, 182.48 [.05]
Model 2 128.28, 182.5, 182.48 [.02]

I re-zero and run it again.

Twin 128.46, 182.56, 182.49 [.06]
Schitzo 128.28, 182.5 - 182.46 [.04] 2 episodes
Model 1 128.37, 182.43 - 182.48 [.05]
Model 2 128.28, 182.5 - 182.48 [.02]

Calibrate, rinse and repeat

Twin 129.3 182.5 - 182.58 [.03]
Schitzo 128.26, 182.48 - 182.42 [.06] 3 episodes
Model 1 128.35, 182.39 - 182.4 [.01]
Model 2 128.28, 185.5, 182.48 [.02]

Big take here is these scales for what ever reason don't like to have a tare weight set...Including the FA scale (changes .1 grain 70% of the time when I zero, but I have to zero it to get it in auto). The included metal tray does fine, but no funnel. PITA now since I have to transfer to the funnel tray but the job is getting done with less variation.

The Twin is being sent back as unreliable. Schitzo is heading for the trash, Model 1 is in backup (reads in .01 increments), Model 2 (reads in .02 increments) is primary validation.

Now here is the other crap ball. As I am doing my testing, I use the FA scale to double check what the milligram scales are reading if it looks weird. The Plastic powder tray/funnel as I approached the FA scale to place it it on the pedestal, the scale would jump .3 grains. WTF? I wipe it down with an anti static cloth (dryer sheet) and same thing. OK, now we use a long pair of hemostats and the same thing, so it's not my hand or me causing this. Turn off the lights, Isolate the scale from all other EM devices and no change. Metal tray does just fine, but the plastic for what ever reason is my problem with the .3gr preload. Arrrrgh

So, those of you that have read this far, if you have both plastic and metal powder trays for your non analog scale, let me know if you are seeing the same thing with tare vs non tare weights, and scale jump. ***Second Edit - Also watch your tare readings. May go to zero every time, but does the actual tare weight stay the same? I.E. - -128.4gr? On a tenths scale, a .1 grain change could actually be in a .2 range.



***Hundredths???? A bit anal. Aim small, miss small...right?. That 15fps change in .5gr is a 12" difference at 1 mile. That turns into a miss on that bloody 1 MOA plate if your are a .5 moa shooter. edited - typo changed to .5 grain from .05.

[grayfox]

I'm not a hundreths guy...
that said, the variances could be, other than internal electronics or line voltage/noise variations, stray EM effect, static, or temperature/air flow. Don't know which one I would suspect. Could be line noise making those particularly stray/schizoid deviations...

Your model #2, that is a 0.02 spec scale, seems to me to be the most consistent, differing only by one calibration notch, 0.02.
Any model can vary by 1 of min-division, that's the nature of electronic measurements. Repeatability of high-end electronic measuring devices can still vary by +/- 0.5 of the min sensitivity, even when measuring the same object. So a 0.02 variance of a 0.02-sensitive scale, I'd say that is to be expected.
Now a mirror-backed super sensitive manual scale, might do "better", assuming your eyes are good enough.

One other comment, in your post you mention 15 fps/0.05 grain deviation... is that a typo, for a case as large as PRC... 0.1 gr in a 223 or 6.5G case might be 10 fps, which is why I ask.

[Draftpick]

The plastic has been know to have static on scales, especially this time of the year in the colder months. I only use metal pans on my scales.

[SCJim]

read the entire rant and still have no idea of what brand scale or scales you are having issues with. For whatever it is worth if one of those scales use a 123 gram board and it is below 65F in your reloading room the temperature can well be the problem. I have a Tree 123 backup scale that works great in the house but take it to the garage in cold weather and it has the same problem you are experiencing.

[Rosecrans1]

In a laboratory setting, you can only use hundredths of a gram with precision accuracy on a thousands of dollar scale on a granite or marble base and with an enclosure around the scale with no RF or static electricity buildup around.
To get hundreds of a grain on a very inexpensive mostly Chinese thrown together unit is asking for a headache.
Humidity, temperature, RF from flouro-lighting and a host of other factors are against you.

[Old Bob]

I had a GemPro 250 scale go schizo. After cal it would run OK for about 30min & then readings would start fluctuating up & down. Tried re-cal - no help; shut-down, re-power, re-cal -no help. Tried waiting for about an hour with the scale off. That didn't help any either so I waited 24 hours & that seemed to work but then it would go schizo again after 30min. I used this scale problem free for about 10 years so I figured it was on it's last legs but wanted to try a few more things before giving it the Heave-Ho.

I wound the power cord through a ferrite core to to see if that eliminated any stray RF or fluctuating input-power problems. I didn't see any change. Next, I powered the scale with an external DC power supply that I have. The DC output of that PS is very stable. I don't remember what the AC ripple voltage was but it's pretty quiet. That seemed to work OK. I did one reloading session (almost an all-nighter) without seeing any schizoid problems. I thought the problem was fixed but then the scale went bonkers again the next time I used it with the external DC PS. Oh well!

I have a new digital scale... a Tree Jewelry scale (+/- .02gn sensitivity) that has been rock steady since I got it. It's Chinese but seems to be well made to me.

I never use the plastic specimen/powder pans that come with scales these days. The pans I use are the metal ones from my original RCBS balance scales.

[SCJim]

Pretty sure that 99.99 % of the scales on the market sold now have Chinese boards in them. One of my most reliable scales , a Gem 20, cost me 20 bucks a couple of years ago. That little scale works wonderfully as a range scale whether it is 30F or 99F. I have verified it many a time against my A&D 120. My Tree 123 works great also, as long as I use it it in + 65F temps, which is no problem now that my reloading room is in the house.

[tdbru]

put the scale on an anti-static mat and ground the mat. and do not use fluorescent lights. LED or filament.

if you really want a top system: https://autotrickler.com/pages/autotrickler-v4 and read at the bottom, they recommend which scientific balance to go with it. autotrickler v4 recommends the A&D FX-120i scale. Brownells carries them. https://www.brownells.com/reloading/...10090302008005

this setup is what the top F-Class shooters in our club are using. So you're looking at ~ $1500 to get what these guys are using, but they're claiming weighing to the grain of powder with repeatability. I'm sure the A&D scale has recommendations on how to setup and use them to ensure the precision of the scale that's advertised.

more than I can justify at the moment, but it'll solve your repeatability and stability issues.
-tdbru

[tdbru]

I should have made it more clear. weighing to the kernel (not grain) of powder. i.e. individual powder kernel. to me a powder grain is a single kernel of powder, but I suppose by saying grain it could get confused with the measurement system being used (grain system) the scale has 0.02gr. resolution. the auto-trickler sits on top of the balance. I've seen a setup working. would be nice, but pretty pricey.
-tdbru

[northdude]

so basically your expecting chinese shit to be super accurate??

[Sticks]

Original post edited and added to for clarification.

Grayfox - Just referring to my original load work up log from 2018, taking into account the 3 shot average fps, SD and ES from 53.5gr, 54.0gr and 54.5gr, was a 30fps from hi to low, and the ES/SD in the 10/15 area. .5 grain - 15 fps based off my averages. Yes, typo since most of the "Rant" was about hundredths. Corrected now

Since most reloading scales read only in tenths, they are rounding one direction or the other. Depending on the programming that is not defined, we can assume that a weight of 54.0 is anywhere from 53.5 to 54.5. Could be just flat dropping the hundredths. Either way, 1 Full grain fluctuation potential, and depending on your load development success and target speed, you may not have a full grain or 2 to play around in with little deviation in FPS that would be acceptable at 1k yards, let alone 1760/mile. I've seen people you tube or post their load work where they have a node with low ES/SD and +/- 20fps over a 2 grain spread. Yay for them. I generally land in the 40s, occasionally mid 20s over a 1.0gr change in my best node.

If all I did was blast away at dirt clods at 100y, I would not care about the 50fps. I don't like to play under 400 unless I am competing with the family on 3/4 moa targets on a family gun day. The Grendel is handicapped enough with speed when we start playing at 600+ Lot of drop, lot of wind holdover.

The more I start running numbers through a calc, the more frustrated I become. A 3" drop difference at 1k with 50fps is laughable.

"Hey, I can shoot .5 MOA all day long at 100y. A 10" target at 1k is a no brainier, I got 5 extra inches of safety buffer."

I do know that past 400y little flaws in your shooting skill start compounding and get really, really ugly at 600+.

I have been shooting the SRM for 4 years now and have yet to break 40pts out of 60.

The Scales used were, Twin and Schitzo, Model 1, and Model 2.

[Oryx]

I have the Autotrickler with A&D FX120 and definitely learned that it is necessary to let the scale warm up for 30-40 min. Additionally, I have to make sure that the heat/AC fan is not blowing (even with the scale shroud) as it is very sensitive to air movements around it as well. As mentioned previously, static electricity is also something to pay attention to and try to manage.

Since you're also comparing 4 scales, I'd make sure you are using the recommended range of calibration weights for the scale capacities ... the same one may not be appropriate for all (ie: don't use a 10g weight when you should be using 100g and vv).

I've been in the camp of chasing perfection for things you can control (as well as some under the illusion of control) and while it rarely hurts, it doesn't always get you where you want to go.

Best of luck!

[grayfox]

[grayfox]

RF, noise and line voltage spikes are typically (and cheaply) filtered out by capacitor filters in the input power supply, and the cheaper capacitors can and do degrade over time, losing their filter ability. That's the sort of input voltage filter I would expect to see in a small, cheaper than normal chinesium circuit board. Some will be good, some will be less so. Some will be junk. Just sayin'.

[SCJim]

Just my opinion here but if you are doing your load development you should have a range of .1 or .2 grains on either side of the target weight where the velocity should be fairly flat. That being said when developing the load I like to get as exact as possible so that I have a reasonably good idea of where those flat spots occur.