My digital scale seems to vary by + 0.8 grains from day to day

[glassblower]

New Dillon XL-650, scale, etc

Day 1 - Set powder load to 5.2, measured a number of powder loads with a variation of +/- 0.1, called it a day

Day 2 - Re-checked powder load before starting and discovered it was now at 6.0. Checked tightness of everything, re-read manual, rechecked everything. Set powder load to 5.2, measured a number of powder loads with a variation of +/- 0.1, called it a day

Day 3 - Re-checked powder load before starting and discovered it was now at 6.0, again. Fiddled with it, ensured the white square fully moved from one end to the other,

put 4 loads into measure cup and averaged, still 6.0,

read BE forums,

removed shell plate, cleaned and adjusted as mentioned in forums.

Removed powder system, emptied, removed small powder bar, no foreign matter (not even a bullet),

Cycled powder mechanism and watched the powder bar move a full cycle, it moved smoothly and fully. Powder adjustment screw was firm.

Re-installed powder system (did not adjust), loaded with powder, filled a number of cases, load now measured as 5.7

loaded 10 cases, adding each to the measure cup, noting the measured value as each was added. Average was 5.75 as was the total divided by 10.

Created 2 10 load measures and put them aside. Read BE forums. Called it a day.

Day 4 - Measured the 2 10 load measures from the day before, both had gained 0.8 grains. NUTZ!

From reading the various posts, it seems that a scale having an actual problem is rare and the error is usually caused by the operator. I've calibrated the scale a number of times, put new batteries in it, made sure it is on a stable surface, turned off the fluorescent lights, held my breath when measuring (although I did fart during one measure)

Even before making this post, I went back, re-did the cumulative 10 load measure, it read 58.3, closer, but still off from the individual measures.

Any suggestions as to what to try next?

[markcic]

What powder?

Is the scale calibrated?

[Jeff686]

Couple of ideas:

Powder measure is volumetric, not mass. Powder can settle, given time and/or vibration. Think about all the air at the top of a bag of chips. When filled, but bag is full, but by the time the bag hits the shelves, it appears half full from settling.

Maybe your powder is settling, and the first drop of the day is more compact, and therefore heavier. If you run your case cleaner nearby, or the furnace, or a fan, or a compressor, or whatever... it could compress even more. Subsequent drops would be less compacted, and therefore less weight.

or

How humid is it? Are you keeping the powder in the measure hopper overnight, or in the original jug? Powder jugs are designed to minimize WVTR (water vapor transfer rate). Powder is very dry, coming out of the jug. WVTR for the hopper is high. It is likey the powder could absorb considerable moisture. I don't know how much, but it is possible.

[Joe4d]

You have a fan on ? I always have had good results with an old fashioned balance beam scale, zero it and make sure its level and your done, loads are the same day after day month after month, I keep powder in the hopper till it is used up sometimes days sometimes months, doesnt seem to make alot of difference.

[Sarge]

Initially I thought you were only having problems with the first few throws of a session. It is well discussed here that Dillons will throw heavy charges at the beginning of a session. I usually throw ten right back in the hopper before I start measuring.

[RogerT]

Why not use a bullet as check weight? With that all ususal variables are neglectable, it should not vary in weight from day to day....

That gives you an idea of how much the scale varies, or not.

[glassblower]

All great suggestions, thanks. The powder I am using is Vihtavuori N340. After I noticed variations in the weight from day to day, I would cycle a number of charges before measuring and then adding 4-10 charges to the measuring cup and averaging the charge. I've also calibrated the scale several times. As a newbie reloader, I need to find the confidence that either the scale or powder measure is consistent. Right now. I'm not sure about either. I've thought about getting another scale and comparing, the one I have cost $75 and I'm thinking that I should get a less expensive one just to see how it compares.

[The_Vigilante]

If you buy another scale, buy a balance beam scale. The Dillon or RCBS balance beam scales are a good buy and you can use it to check the digital scale for accuracy.

[Corey]

calibration and check weights are essential for digital scales. makes sure its reading what it should. Make sure there are no air vents/fans/etc in the area and it does need to be on a level surface. Make sure the powder is being wieghed in the same part of the pan each time. powder on one side may lead to slightly different readings than powder in the middle of the pan. Cycle 5-10 throws thru the measure to get things "warmed up" and cycling smooth then measure one to see what its at. As others have said, if you get another scale, get a beam scale as a comparison. I use mine EVERY time i get set to reload anything, even if im using a digi-scale for my rifle loads.

[btm_54]

Do you have your cell phone in the room?

I think they can affect the accuracy of electronic equipment.

My Lyman was affected by my cell phone from up to 10' away.

Regards,

btm

[Powder Finger]

I can't find it right now but it's on either 6mmbr.com or benchrest central.com,

are articles on scale drift, accuracy and what to do about it.

In this case if you have a load that checked the FPS you want don't change the measure. Just load, especially if it's a major match.

[Powder Finger]

Found a couple

http://bulletin.accurateshooter.com/2007/07/weight-drift-on-digital-scales-yes-its-real/

http://bulletin.accurateshooter.com/2009/11/inexpensive-noise-filter-helps-reduce-scale-drift-problems/