Digital scale drift?

[Potashminer]

I am new to this RCBS ChargeMaster Lite - just did my first 30 loads with it - actually a pressure series, so was 10 increments, 0.5 grains apart.

So, I notice it is smart enough to indicate when the charge is "Under" what I asked for, and had a couple that showed "Over" what I asked for - I did see a clump of Varget "logs" fall off the dispensing tube into the pan - makes sense those might have ended up as "Over".

However, seems as if the entire thing very dependant on the signal from the load cell. I did calibrate before starting - thing has been plugged in and turned on for day and a half. I had read on this site and others about digital scale "drift" - how does the user know that is happening?? Is it as simple as weighing something when starting, and then weighing it again when finished? Kind of too late by then??

 

[yomomma]

Air currents and Fluorescent lights have been known to cause drift.

When I do use an electronic scale I tend to re-zero regularly, every ten rounds or so.

Might be overkill but thats just the way I do it

 

[Potashminer]

Okay - for whatever reason there is a "Zero" button on the machine - but every time I took the pan off and replaced it, the display was again reading "0.0". Overhead lights are a 48" LED light bar. Laptop and cell phone were placed on other side of the room on a steel tool chest. At this location on my work bench, my laptop is picking up LAN (?) signals from several neighbours, so not like I can eliminate all EM stuff in the air here? The two iTV boxes can pick up my cell phone here in the garage, from inside the house. I can pick up the "hot spot" from my wife's cell phone, which is in the house.

I'm having a smoke now that everything is put away - cigarette smoke from ashtray going pretty much straight up, so not much here for air currents.

But, still my question - how does a user know that "drift" is occurring?? Maybe I am misunderstanding what that is?? My understanding was the thing is displaying one value, but true, actual value is a different number - external influences, age, etc. can cause that difference to change and get worse - I think??

 

[Munkey1973]

If the CM Lites have the same size tube as the CM 1500s ... then stick a small piece of McDonalds straw in there.... sounds hokey but it really will cut down on the number of over/under charges... seriously

My interpretation of "drift" is that zero is not holding (i.e. put an empty pan back on the scale and it doesn't signal the dispenser to drop another load).
I never (ever) had this problem when I had a Chargemaster...

When I moved using a FX 120-1 and Autotrickler V3.... had this problem... a lot!

I implemented 2 solutions at the same time (so I don't know precisely the problem was) and now its highly reliable.

(1) my home has dirty power .. an of electrical mystery light show when things go on and off. So I installed a quality constant power source dedicated to my scale.

(2) I switched from fluorescent overhead lights in my workshop to LED (and made the lights as high as I could go).... I've seen many threads that fluorescent lights emiiting radio waves that mess with scales.

 

[Potashminer]

In another life time, I was involved in a dispute that required some sampling to be done - so the consultants insisted that a NIOSH protocol was going to be followed. Senior lawyers insisted there was exactly ONE way to do this correctly. The lab scale was Mettler brand - I do not remember the model. Was purported to be accurate to 5 or 6 places after the decimal point - so .00001 or .000001 grams - I do not remember which. That was not good enough for the lawyers - had to also be validly calibrated - that required shipping to a centre in USA - New Jersey (?) - and then certified as calibrated to a standard traceable to NIST. And, I recall the certificate had an expiry date - like a year out or so. The fellow who was going to operate the scale (i.e. to do the weighing) had an M.Sc. in Chemistry and a number of years research in the field - he was actually quite keen on this "do it correctly" stuff - likely from his younger research days, I guess.

So, I am not unfamiliar with "accurate" scale or "precise measurements" - but many times do not have to go that far - sometimes "close" is "good enough". But if "drift" means I can weigh the same thing at three different times, and get three different numbers, something within me doesn't like that... Is like trying to read to .0001" on a micrometer - sheesh - is about how tight you turn on it!!! Thinking to try to turn stuff on my lathe to .0001", and found out that I could not even reliably measure to that!!!

 

[Burton Urnie]

Would it work to have a set of beam scales zeroed with the same pan setting side by each,
then,
Take pan with powder from digital to the beam scales?

 

[Potashminer]

Would it work to have a set of beam scales zeroed with the same pan setting side by each,
then,
Take pan with powder from digital to the beam scales?

I just did that earlier today - so I calibrated the RCBS CM Lite as per instructions - confirmed that the Hornady beam scale was reading "0" when all set at "0.0". I threw 10 charges with RCBS thing set at 35.0 grains - weighed each throw on the beam scale - 8 out of ten were between 0.2 grains light and 0.2 grains heavy as per the beam scale. The very first two throws from the RCBS thing were .45 and .35 grains light compared to the Hornady beam scale. Each machine says accurate within 0.1 grains. So that means each could be up to 0.1 grain high or 0.1 grain low - so maybe 0.2 difference is within the accuracy level of each machine, when combined?

Now getting myself confused - started out wondering what is "drift" on a digital scale - now thinking what is absolute accuracy, one scale versus another. Not the same thing, but relevant!!!

 

[Potashminer]

Really "spinning" now - so both scales have "accuracy" capability of 0.1 grains. Set CM Lite to deliver 35.0 grains - could get a "true" weight of 34.9 to 35.1 grains delivered, within that "accuracy" range. Then, on to that Hornady beam scale - so a "light" one - true weight as 34.9 grains - could read 34.8 to 35.0 on the beam scale - its accuracy. Or a "heavy" one - true weight as 35.1 grains - could read 35.0 to 35.2 grains on that beam scale. So, set the CM Lite to 35.0 grains - within 0.1 grain accuracy on each scale, could read from 34.8 to 35.2 on the Hornady beam scale - 8 out of 10 throws did that. Very first two thrown from that CM did not.

Does not help me understand what is "drift" on a digital scale?

 

[Deathrawt]

What I consider drift is when the scale doesn’t reset to zero after you dump the powder from the tray
It will go to +1 or 2 and not begin dispensing the next t charge
I’ve also had it where it finishes it’s charge properly, say 50grains for example and I will go to the can or grab a pop or something
5min later I come back to it and it will show 52 grains and state overcharge
I don’t know what causes it but both my chargemaster lite and hornady scale do it

 

[Potashminer]

What you describe is exactly why I want to retire my Lyman DPS 3 - it does exactly that - throws a charge - says it is there - within several seconds decides to display a different weight for that charge that was just sitting there - then throws a "calibration" error, which wants the calibration done again - and that lasts for about 3 or 4 throws and then back to the errors again. At least it is smart enough to know that what it is doing is not "correct"... I bought that machine in 2008 - I think of it as "new" - maybe is very old so far as electronic gizmos go...

 

[coleman1495]

Well I’ve operated lab scales for every job I’ve had. Proper scales like a Mettler Toledo do not drift. Thats not to say that lab scales aren’t still checked and calibrated but I haven’t seen one out in 10 years of operating them.
The Chargemasters have cheap crappy scales. It’s unfortunate but thats what 350$ buys you. I have 2 Chargemaster Lites and they are both the same, both unreliable. I don’t know what causes drift within the load cell but it is a problem with low end scales.

I don’t think its fair to say that all of your inaccuracy with the Chargemasters come from drift. It is very likely that it could throw a charge, lets say 35.0gn and it’s actually 35.2gn. This could be despite your scale not losing zero, the check weights still reading correctly, and the Chargemaster doesn’t indicate an over/under charge.

 

[Bubba Yugga]

Has anyone considered them damn UFOs passing overhead with their antigrav flux fields messing stuff up?

 

[Potashminer]

...

I don’t think its fair to say that all of your inaccuracy with the Chargemasters come from drift. It is very likely that it could throw a charge, lets say 35.0gn and it’s actually 35.2gn. This could be despite your scale not losing zero, the check weights still reading correctly, and the Chargemaster doesn’t indicate an over/under charge.

I was relying on the specifications - page 7 of the Product Instructions - apparently up to 500 grains is to be plus or minus 0.1 grain - so when set to deliver 35.0 grains, I would have expected an actual true weight of 34.9 to 35.1 grains. I probably would have to live with that, since that is the same tolerance for the Hornady beam scale that I have been using...

Maybe I misunderstood what "drift" is - I had thought it might be reading out 35.0 grains, but true weight is changing 35.1, 35.2, 35.3 and so on.

 

[5.45]

Well I’ve operated lab scales for every job I’ve had. Proper scales like a Mettler Toledo do not drift. Thats not to say that lab scales aren’t still checked and calibrated but I haven’t seen one out in 10 years of operating them.
The Chargemasters have cheap crappy scales. It’s unfortunate but thats what 350$ buys you. I have 2 Chargemaster Lites and they are both the same, both unreliable. I don’t know what causes drift within the load cell but it is a problem with low end scales.

I don’t think its fair to say that all of your inaccuracy with the Chargemasters come from drift. It is very likely that it could throw a charge, lets say 35.0gn and it’s actually 35.2gn. This could be despite your scale not losing zero, the check weights still reading correctly, and the Chargemaster doesn’t indicate an over/under charge.

+1. I also had a cheaper Ohaus in the lab that would show 127.5 g, and then it slowly changed to 127.6, 127.7 etc. It wasn't a big deal for that particular use case.

The unit in question shows "under" or "over" - when? E.g. your target weight is 37.0 gn, would 36.9 gn trigger the "under" label?

I am lazy, so I just weigh the primed case, throw a charge with the Dillon 550 powder measure, weigh the case again, if it is within +/- 5 mg, seat the bullet, otherwise dump the powder and repeat. It is faster than counting and dropping those Varget logs one by one.

A good node should tolerate some inconsistency.

 

[Potashminer]

+1. I also had a cheaper Ohaus in the lab that would show 127.5 g, and then it slowly changed to 127.6, 127.7 etc. It wasn't a big deal for that particular use case.

The unit in question shows "under" or "over" - when? E.g. your target weight is 37.0 gn, would 36.9 gn trigger the "under" label?

I am lazy, so I just weigh the primed case, throw a charge with the Dillon 550 powder measure, weigh the case again, if it is within +/- 5 mg, seat the bullet, otherwise dump the powder and repeat. It is faster than counting and dropping those Varget logs one by one.

A good node should tolerate some inconsistency.

"Over" and "Under" - I am just guessing, but appears to relate to what you asked for, versus what the display is showing - so, if I asked for 35.0 grains, and if display shows 34.9 or less, the "Under" is shown. When display is showing 35.0, both "Over" and "Under" are not showing. A few times it went to 35.1 on the display - at those times, the "Over" came on. Is a learning curve for me - if the thing is 0.1 Grains accuracy, then when the display is reading 35.0, the true weight should be within 0.1 grain of that number - so true weight could be 34.9 to 35.1 grains, even though display is showing 35.0. I never tried with the GRAMS / milligrams mode - I was only using the GRAINS mode.

Your first statement - seeing the display slowly change - is what I see on the Lyman DPS 3 - as if the computer is changing its mind about what weight is on that pan - shows a value on the display, then that value that is displayed changes over several minutes... The weight in the pan did not change, but the display does. Maybe the change in the display is what people are calling "drift"?

FYI - that CM Lite has been "On" for more than two days now - say 16 hours since I last used it - display is showing "0.0" with nothing in the pan. My laptop and cell phone have been within 3 feet of it for past 12 hours...

 

[coleman1495]

+1. I also had a cheaper Ohaus in the lab that would show 127.5 g, and then it slowly changed to 127.6, 127.7 etc. It wasn't a big deal for that particular use case.

The unit in question shows "under" or "over" - when? E.g. your target weight is 37.0 gn, would 36.9 gn trigger the "under" label?

I am lazy, so I just weigh the primed case, throw a charge with the Dillon 550 powder measure, weigh the case again, if it is within +/- 5 mg, seat the bullet, otherwise dump the powder and repeat. It is faster than counting and dropping those Varget logs one by one.

A good node should tolerate some inconsistency.

No being over/under on a Chargemaster won’t necessarily trigger the “over/under” warning.
Unfortunately there isn’t any real way of detecting this unless your checking the charges on a proper lab balance.
I agree that a good node will tolerate the variance unless your doing some extreme long range or something.

 

[kthomas]

If the CM Lites have the same size tube as the CM 1500s ... then stick a small piece of McDonalds straw in there.... sounds hokey but it really will cut down on the number of over/under charges... seriously

My interpretation of "drift" is that zero is not holding (i.e. put an empty pan back on the scale and it doesn't signal the dispenser to drop another load).
I never (ever) had this problem when I had a Chargemaster...

When I moved using a FX 120-1 and Autotrickler V3.... had this problem... a lot!

I implemented 2 solutions at the same time (so I don't know precisely the problem was) and now its highly reliable.

(1) my home has dirty power .. an of electrical mystery light show when things go on and off. So I installed a quality constant power source dedicated to my scale.

(2) I switched from fluorescent overhead lights in my workshop to LED (and made the lights as high as I could go).... I've seen many threads that fluorescent lights emiiting radio waves that mess with scales.

I've never measured drift in my autotrickler w/FX-120i setup, but heard it could be a problem with lab quality scales, so I made sure I didn't have that problem.

I bought a UPS that "cleans up" the incoming power supply, providing stable voltage to the scale.

I've also heard that labs will keep their scales on 100% of the time to prevent drift. This I don't do, but I will power up my scale about an hour or so before I start reloading.

 

[5.45]

I never tried with the GRAMS / milligrams mode - I was only using the GRAINS mode.

Maybe give it a try. My current scale is an el cheapo Frankford Arsenal. I experimented a little bit, and it seems it works natively in grams, with 0.005 g resolution. Switched to grains mode, it still measures in grams, and then converts to grains, +/- 0.1 gn. 0.005 g is about 0.08 grain, so the conversion doesn’t work very well for certain values.

Now my curiosity has been triggered. Going to check the FA against an analytical Sartorius.

 

[coleman1495]

I've never measured drift in my autotrickler w/FX-120i setup, but heard it could be a problem with lab quality scales, so I made sure I didn't have that problem.

I bought a UPS that "cleans up" the incoming power supply, providing stable voltage to the scale.

I've also heard that labs will keep their scales on 100% of the time to prevent drift. This I don't do, but I will power up my scale about an hour or so before I start reloading.

I’ve never heard of turning lab scales off to prevent drift. Thats not a real thing.
Also the use of a UPS is unnecessary with a Mettler Toledo. I’ve also never never heard of that being necessary. This is also dealing with balances that are more accurate than your FX 120

 

[fingers284]

To me ( after 20 yrs of using a digital powder charge dispenser) scale drift is not throwing over or under charges...scale drift is when a charge is thrown, the scale gives a steady reading for a few seconds and then the reading starts to climb or descend from original value to another and then to another. this is "drift"

The problems you describe are more than likely variations in how your scale handles different powder kernels. Tube speed, tube internal threads & powder consistency all can change charge characteristics...I think your scale is just making you aware that your charges are not being metered efficiently/consistently.

More to say but have to go for a bit.