gempro-baldeagle-?-elec scale

[shoot4fun]

My Gempro was, and my FX120 is, plugged into a power strip with a filter built in. I have removed all my fluorescent lighting in the shop and replaced with LED (as much for the best light as for the lack of interference). The GP250 is a a very accurate scale but just a bit slower to respond to changes than I wanted (lack of patience). Again, I have a set of check weights and the GP250 was right on and didn't drift. I think the key is keeping any digital scale warmed up so I leave both my Chargemasters and my FX120 on 24 hrs a day (did the same with the GemPro). Now, as an added bonus, I have sent my old 10-10 scale to Scott for a tune-up.

 

[brokeasajoke]

My 10-10 left out today to sparker. Electronic scale will ne nice for sorting. I too am replacing lighting with LED. Closest fluorescent is 15ft away or more now.

 

[Twoboxer]

So what are some of you guys doing to minimize drift on gempro 250? Seem these scales are in use heavily in our sport. A sticky would be nice.

Here's some of my personal experience, FWIW:

RF: I've heard strain gauge balances referred to as "RF receivers". So, I tried to eliminate all RF noise . . . fluorescents, bluetooth, Wifi signals, microwaves, wireless telephones, etc. Some may not affect your scale in your environment - when something seems to affect it, you'll need to track it down. It can come from strange places as well. I had a Pact dispenser that required two separate power supplies, and every time the pairs of wires moved relative to each other or other power cords, the scale would flutter. I bought a lab grade power supply for my GemPro 250 thinking it would eliminate line noise and any wall transformer issues. It had no effect on my problems. Does that mean it filtered out supply line noise, or was the supply line and the transformer never an issue? Don't know.

Static discharge: In low humidity environments, your scale may flutter as your hand approaches it. Test by grounding yourself. A simple way is to plug in a wall-wart transformer and hold the output plug. If that eliminates the problem, you can use a more elegant solution Couple of days ago in my basement reloading room I could not approach let alone touch my Chargemaster without it changing to "unstable". The transformer plug trick worked, and I have a static mat arriving tomorrow. (BTW, it also affected the A&D FX 120I, though only when I touched it.)

Air currents: Sensitive scales will react to air currents as pressure changes above it. I used an incandescent pole lamp as a work light from over my shoulder, and the heat from the lamp created an air current . . . which got interrupted every time my hand passed through them, and the GemPro (and others) would flutter. My own solution was to use LED lighting and put the scale inside a cheap 15" storage cube.

Limited resolution: Quoting from this source: http://balance.balances.com/scales/1223 . . .
"Strain gauges work fine for bathroom scale, kitchen scales, general purpose digital scales up to 20,000 divisions. To determine the amount of division a scale has you simply divide the weighing capacity by the readability. So [eg] the VIC123 was 120 grams weighing capacity and readability was 0.001 grams. Thus 120g / 0.001g weighs 120,000 divisions. This is impossible to get from a strain gauge."

Not directly related to your question, but related to the overall problem:

Rezeroing: A lot depends on the programming inside the scale. When you need to rezero every so often . . . what exactly happens? Do multiple rezeroings build in a cumulative error? I don't know, but I'd recheck with a check weight before moving on.

Honestly, all I know for sure is I put my 7th scale, an A&D FX120I, in a 15" storage cube and it works just like you'd want a scale to work . . . even with fluorescent lighting turned on in the ceiling above it. It reads to 0.02gr. The only time it flutters is when the weight is (eg) XX.03gr. It may not decide between XX.02 or XX.04 for a while.

 

[brokeasajoke]

So i purchased a gempro from a forum member. Plugged it up and placed check weight on. came back a few hours later and the weight checked .1 gr heaver. I load in a cold garage and usually warm it with a wood stove some times it starts out very cold. Would just leaving this scale on for a few hours or a day be acceptable? Thanks. just curious to others experiences.

 

[BoydAllen]

Simply put, what you experienced is not important at all. What is important is that if you weigh something, and then then weigh it again, that it weigh the same (within reasonable limits). We do not weigh powder, or anything else for that matter, the way that you did your test. I have a Bald Eagle, I have spent a lot of time using a Gem Pro 250. Within the limits of their designs (load cell) they both are good scales. One costs more than the other. IMO if some people were given a scale that measured grains to four places, they would worry about how consistently that last digit read. If you want instantaneous response when trickling, get a magnetic force restoration scale. If you do not, and cannot justify the expenditure, I suggest that you may want to use a tuned balance AND have a decent load scale too. Disclaimer: Because I do not compete at long range, I have no need to chase single digit ESs.

 

[brokeasajoke]

Im not worrying about .02. it was tenth difference. Don't want to blow my face up lol though a tenth probably wont put me in that much danger since i usually never chase max loads. Scott has my 10-10 scale to tune. Nor do I compete either. I just strive for the best ammo I can put together.

 

[BoydAllen]

My point is that none of us leave a powder charge on a scale for a few hours. It is a characteristic of load cell scales that they do not hold up to that kind of testing well, but since we do not use them that way it does not matter. Try this. Weigh something, then come back a few hours later, rezero as needed, and weigh the same thing. Let us know what happens.

 

[brokeasajoke]

Yes thats what I done. I didn't leave it on the scale. Sorry for confusion. just checked again and it is reading .04-.06 higher without any warm up time. Maybe just some temp stabilization. Should I keep it in temp controlled and take it to cold garage when im gonna use it. Gonna try and find a small piece of granite counter top to put scales on and put granite on a layer of rubber.

 

[Sheldon N]

One thing to keep in mind is that strain gauge scales are sensitive to electronic interference, and to temperature change. Either can cause the scale to drift. Don't load with a cell phone in your pocket, and don't load in an environment where the temp is not constant.

I use a strain gauge scale and also load in the garage which is adjacent to heated space but not heated. It stays a pretty constant temp in the mid 50's. I've chosen to just wear shoes and a sweatshirt when I load, and not try to warm up the garage by leaving the door into the house open. The times that I've done that it's caused me grief, but does pretty well otherwise.

Starting with a cold room then warming it up with a woodstove right when you go to reload is asking for drift problems.

 

[Mozella]

.... snip............

GemPro is more than accurate enough to load powder to the kernel.
You need to watch drift by checking that the powder pan rezeros properly after each round, and by referencing a fixed weight object periodically during loading. I have a screw that I filed down that weighs exactly 45.00g and I check every 5 rounds or so.
GemPro is more difficult to trickle. You need to guess how many kernels to add, then lift and reset the pan to see if you were right........... snip........

Your (longer) post mirrors my experience with the Gem Pro. I gave up trying to throw short loads and trickle up using my Gem Pro 250. It was just too tedious. The scale tended to become "confused" during trickling, first not responding at all, and then producing a new weight reading which proved to be in error. I don't know exactly how the Gem Pro works; perhaps an expert can chime in. I get the feeling, when I watch the scale display, that it tries to correct to zero when I place the empty pan on the scale and it does that pretty well. But I wonder if it tries to find that zero while the pan is off the scale and gets itself confused. Anyhow, for whatever reason, the scale seems to do a simple weighing procedure quite nicely. But if you fiddle around as you normally do when trickling powder, it just doesn't perform very well.

The good news is that I've found it works very well in conjunction with my new RCBS Charge Master. The Charge Master won't produce loads accurate enough to trust because from time to time it makes a load too large or small to accept because I need better accuracy than the published .1gr tolerance. It usually does better than advertised, but not all the time. In other words, it has a very high probability of making a load which requires a correction of only one or two kernels of powder, so that's how I use it. Double checking each charge on the Gem Pro is easy if you only have to add or subtract a kernel or two. Usually it requires me to lift and preposition the pan. Using that technique, I can make loads reasonably quickly.

If I can't correct the load in one attempt, I dump the powder into the case, recheck the zero tare weight of the empty pan, dump the powder out of the case and into the Gem Pro pan again, and check the weight. Normally it is within .02gr (the limits of resolution for the Gem Pro).

If the Charge Master produces a load which takes more than two kernels to correct, I normally reject it and ask for another one. Unfortunately, the Charge Master will sometimes make a load which misses the mark by more than .10gr but not very often.

In summary, the Charge Master can't be trusted to outperform it's published tolerance even though it usually does. In fairness, I am trying to produce loads to a tight tolerance, so I'm not blaming the Charge Master; it's performing better than advertised. The Gem Pro is too fiddly for trickling unless the first weighing attempt is VERY close to your target. But working together and recognizing the need to reject a load from time to time (from either of the devices) these two machines are pretty good. I can produce loads within .02grains of my target pretty quickly and easily enough so that I don't have to curse............... too much anyway.