Powder weight loss?

[Valornor]

I have a Hornady electronic scale and dispenser for a few years now. I love it. However I have noticed that if I leave a measured charge sitting on the scale it mysteriously becomes lighter over time. If it came out as 42.0 grains it might "lighten" to 41.5 or 41.0 grains after sitting out for a few minutes.

I have never noticed a issue with my loads and the chronograph has never picked up any alarming dips in velocity. Nor have any rounds failed to cycle. I'm just curious as to what might cause it? I don't imagine powder out gasses. I figure it's the scale...

[Nick_C_S]

Somebody's going to chime in here with a technical explanation. But I'm here to tell you that it's a phenomenon I've experienced with every electronic scale I've ever used, for any application. Not just powder measure scales.

I use a gravity/balance scale. Takes a little extra time, but its set up is a ritual I enjoy. It's part of what makes this hobby so therapeutic. And I set my powder charges with complete confidence and no mental question marks.

[1stmar]

I have a hornady auto charge and it does the same thing. I can't explain why. I take my change from the hornady right to an rcbs 505 and reweigh every charge. Don't ask why, I guess cuz it only takes a second to do. I'm sure someone will tell me I'm doing something wrong but when I place the pan on the 505 I let the beam rise from the bottom from the weight in the pan and then settle on its own. If it looks like it is off, I will place push down on the pan and let it drop from the top and see where it stops. I know everyone swears by the balance beam but mine seams to have its own idiosyncrasies, the best way to ensure an accurate reading for me is to have the pan swinging a small bit. Otherwise it has a tendency to "stick" and not always settle at the right reading. I don't worry about either scales accuracy because neither of them are ever off from each other by more then .2 grains on a 42+ grain charge. I have a calibration set and frequently check both, they are right on. I just think they both have outside factors that influence them.

[Lucas McCain]

I have the old electronic lyman powder measuer with the balance beam and I also weigh each load with the RCBS balance beam scale. I don't know why but thats just my method.
I believe the technical explanation as to why the digital scales act that way is what the electronic world calls "Hysteresis". Its an intentional lag that is put in system prior to the input for accuracy reasons, as I understand it. That's what some Nerd told me and I didn't know enough about it to argue or question him.

[rox]

How long do you allow to warm-up the balance?

Over what period do you observe this change?

Most electronic balances (in particular strain gauge balances) have zero-tracking functionality to counter this type of drift, but when you leave a load on the balance zero-tracking is effectively disabled. I notice this even with my A&D Fx120i balances when a load was left on the balance for a period of one or two hours (my Denver Apex balances, on the other hand, always seem to be rock steady).

I use two approaches to minimize and counteract this type of drift:

1. Plenty of warm-up time. I try to ensure that balances are switched on 24 hours before I plan to use them. This dramatically reduces the amount of drift. Some folks leave them on 24/7.
   
   
2. Ensure that the balance 'sees' a stable zero for a period during the loading cycle.

For example, consider the following typical loading workflow:

1. Zero the balance with the empty powder pan on the balance (so the balance will indicate the actual charge weight).
   
   
2. Pre-load the pan from a powder measure, then place the nearly-complete charge on the balance.
   
   
3. Trickle up to the final weight, then tip the charge into a case. Now goto step ii).

In this sequence the balance never settles at zero, since the powder pan is pre-loaded before it is placed on the balance. Consequently zero-tracking can't work and the balance can drift unchecked.

One way to avoid this is to zero the balance without the powder pan (you must add the weight of the powder pan to your target weight). Now, when you remove the pan (to tip the charge and pre-load from the measure) the balance can settle at zero and the zero-tracking function can operate.

Some balances also have a separate 'tare' function, which retains the zero but removes the weight of the container from the gross weight, so that zero-tracking can function and the indicated weight excludes the container, but this seems to be rare in high-resolution precision/lab/analytical balances.

[Brian Pfleuger]

Any scale that does that after warm up belongs in the scrap pile. I use an RCBS Chargemaster Combo and it doesn't do anything close to that. It always, always, always weighs the same items within 0.1gr. Sometimes, when I first turn it on it shows 0.1 low and will stabilize at the known number in a few minutes. I've weighed a powder charge MONTHS apart and got the same exact weight.

Any scale that does what you describe is defective and warrantied or scrapped.

[rox]

It definitely shouldn't drift that much within minutes, but repeatability when weighing from zero is a different matter from stability with a static weight in place when you're dealing with drifty strain gauge balances. Last time I analyzed a Chargemaster I found that when it was unable to zero-track it drifted by about 0.1 grains over the course of about 15 dispenses. When allowed to zero-track (like in normal use) it would haul itself back to zero long before such a deviation had arisen.

I wonder how long it would take a CM to deviate by 0.1gr, 0.2 grains etc when there is a static weight in place? I don't have one anymore to find out. Another way to see the heavy zero tracking in action is to see how many kernels it takes to deviate the scale from 0.0 to 0.1, compared with from 10.0 to 10.1. I didn't log my results from that test, but I recall it was a very significant difference.

[Jim Watson]

Agreed, that isn't right. My PACT is not the latest technology and is not perfect but it does not do anything like that. I leave it on all the time so I can resume loading where I left off with no warmup delay.

Time to check out Hornady "customer service."

[Brian Pfleuger]

Rox,

How could it dispense without being allowed to zero track?


I'll turn mine on and put a weight on it and see if it deviates.

[Brian Pfleuger]

I turned it on and let it zero. Placed pan on, shows 166.6gr, which is 0.1gr over. It's about 50 in that room but I left the door open so it'll be warming up in there too. I'll see if it changes as the room and/or the scale it warms up. It should drop to 166.5 but the pan must be very close to 166.55 because it reads 166.5 about 90% of the time but occasionally reads 166.6 even when warm.

Anyhow it's been about 5 minutes and it still shows 166.6.

After 30 minutes, I'll zero it and put the 50 gram check weight on it. I'll leave it on all day and see what it reads tonight.

[rox]

How could it dispense without being allowed to zero track?

As follows:

I arrived at the figures by accident. I was actually trying to see if I could speed-up dispensing by pre-charging the pan to 0.5 grains under setpoint using a measure, then placing the pan on the Chargemaster to do the final trickle. It kind of worked, and in fact the variance (measured to 0.001 grams) was less, since the tube didn't get filled-up by the fast-speed initial fill. But, since the pan arrived part-full the balance never 'saw' zero (per my long post above) so it couldn't zero-track.

[Brian Pfleuger]

Oh, so you're manually trickling? Mine won't auto dispense unless the scale reads zero.

Scale stabilized showing pan at 166.5. I calibrated, zeroed, placed 50 gram check weight. Shows 771.6gr. Will leave until tonight.

[rox]

Oh, so you're manually trickling?

Not what I would call manual trickling, but running the dispenser in manual mode, i.e. press the button to start a single dispense cycle (rather then automatically starting when the pan is placed).

Here are some graphs from that experiment. The first one shows normal dispensing, with a setpoint of 46.0 grains. The moving average starts to deviate but tracks back.

In the second graph the deviation is not corrected. However, the variation from the moving average is less. Corrected to the moving average there is a lower spread/SD of charge variance.

I suspect this could be used to run the CM to dispense improved weight spreads and without the drift, by zeroing the machine without the pan, setting the target weight to include the pan weight, and pre-loading the pan from a measure. It would have to be run in manual mode though, otherwise it would start to dispense with no pan in place.

[TXAZ]

I'm not a powder scale guy but can comment on sensor drift:
(And I dont think your powder is sublimating)

I expect the lack of recent zeroing is the first order cause. If the scale is piezo electric or strain guage based then temperature will affect the results. Even temp compensated will give you a 'close' but not a perfect measurement. Barometric pressure can also make a slight difference.

If you are using a (likely) older inductive or capacitive based sensor, vibration, slight movements, solar wind and flares, or starting a heavy electric load can tweak the "real" result in the lesser decimals.

If you want a super accurate, near-zero drift, highly repeatable lab-standard quality scale, be prepared to pay $1-10K.

Otherwise more frequent zeroing will help.

Hope that helps

[reynolds357]

Its the scale. Definitely not the powder. Set a calibration weight on it and watch the same thing occur.

[RC20]

I bought a cheap Franklyn scale and have those issues as well (drift).

Unlike Brian I elected to play with it and see if I could work with it (not that I don't think he is right about scrap but for now its what I have and I am used to getting things to work right).

I weight my charge pan and then zero the scale (I have written on the pan what it should be).

When I take the pan off I note what the scale reading is. As soon as it drifts a tench, I re-zero the pan and check that its weight what it should.

I cross check loads based on this with my beam scale and they are consistent.

If a scale is really erratic it won't work but this does work on the scale I have.

[Brian Pfleuger]

Interesting test, Rox. With a maximum spread of 0.14gr at 46.0gr, I'd have no interest in improving though.

The Chargemaster was showing 771.5gr when I left home at about 1230.

[Valornor]

Wow this thread exploded over night.

I calibrate my scale every time I use it and it always passes. I then place the pan on the scale and zero it. Then I put in the charge weight. I do the exact same thing minus entering the charge weight when I set it up to spot check my dillion 550 powder thrower.

I do not leave it on 24/7 and I could be using the scale for an hour or five minutes and it will do the same thing. Like I said before, I've owned it for three years and I have never had reason to question the wieghts it measures. Consistency shows on the chronograph and I've had some 20rnd batches where S/D had been within 50fps.

Someone mentioned barametric pressure, that would make sense but it would also mean I am always loading when the pressure is falling. Baring that I am a human barometer, I don't think that's consitant. I should see the scale increase weight randomly too. I'm not seeing that. (I might freak if I did though. Under I can live with over not so much)

I'm satisfied of it's just the product of having cheap electronics. It'd good to know I'm not the only one who's notice or seen this.

[603Country]

I don't have that problem. Just get a good scale. Problem solved.

[Jerry45]

My RCBS Load Master preforms identically to Brian's. Now what I have seen mine do is, if I leave a charge in the pan for a period of time 10 minutes or possibly longer, leave and come back, the charge weigh will have changed. If I dump the powder into empty case, put the pan back on the scale it will usually zero out. If not I zero it. In either case when I pour the powder back in the pan it returns to it's original reading / charge weight. I believe the reason for the change in weight is that the wind / air flow messes with the scale while I'm away and it throws the reading off. The grand-kids just opening and closing the door while I'm there will cause the scale to fluctuate and if it's in the process of dumping powder it WILL throw a heave load. It's pretty touchy, but I consider that a good thing.

[mjes92]

Are you reloading near a Florescent light?

A few years ago I had similar problems with my first expensive plug-in RCBS digital scale. I didn't trust it so I returned it. I purchased a cheap battery operated digital scale for convenience of weighing cast bullets, etc..... Same problem. Just by chance started weighing at a different location away from florescent lights. The scale worked great and quit drifting.

I searched this forum and found others seeing the same problem with digital scales near florescent lights.

Its worth a try to prove or disprove the florescent light theory.

Good luck

[Brian Pfleuger]

Just got home and checked the scale, it still reads 771.5gr. So, it looks like it tends to lose 0.1gr somewhere in the first 15 minutes to 2 hours and then holds that weight for many hours after. Considering that I never leave anything for more than a few seconds, it loses nothing for several minutes and the 0.1gr is irrelevant regardless, there's no issue whatsoever.

I still say that any scale that does what the OP describes is defective and needs repair.

I had one of the $25 Frankford Arsenal scales too... absolute junk. Wouldn't hold a weight long enough to pick up the pan, would stay calibrated, wouldn't weigh the same thing the same weight twice.

[Jerry45]

"Considering that I never leave anything for more than a few seconds,"

You don't have grand-kids do you?

[Valornor]

"Are you reloading near a Florescent light?"

Actually I am. I'll have to give that a try and see if that changes anything.

[1stmar]

I am as well. My charge never sits in the pan for more then a second. Unless I get distracted. It's really not an issue. I don't keep my scale on as I don't have conditioned power, I reload in my garage so temp and humidity are large factors.