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Old June 26, 2011, 08:54 AM   #1
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RCBS Electronic Scale zero point wanders?

I have an RCBS Rangemaster 750 scale that I have had for a couple years. Lately, after I calibrate it and zero it with the pan on, the zero point wanders up and/or down. I typically check every eight thrown charge and when I go to weigh a charge maybe a minute later, the zero has changed. Sometimes by 0.1gr but sometimes has gone to -0.4 or greater. I rechecked the level of my bench top and it is fine, I even insure there is no airflow around the scale from fans, wind, etc.. Starting to worry me a bit, I have to put the empty pan back on, re-zero the scale, then press on. I occaisionally shut it off, recalibrate with the weights, but it will still wander like that? Do you all think it is defective or is this typical? It did not seem to do this when it was new. I am getting concerned about the possiblity of loading too hot without realizing it. Thanks in advance for your input.
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Old June 26, 2011, 09:00 AM   #2
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Did you let it warm up long enough?

Load cells are notorious for thermal drift.
When I plan on reloading I turn the scale on and leave it overnight before using.
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Old June 26, 2011, 09:12 AM   #3
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First thing I would do is get a set of check weights (just to be sure it is measuring correctly) or put a bullet on the side that you can use as a check weight, say a 230 grain 45 ACP (and record the exact weight of that bullet). Then use it later to double check that the scale has not drifted.

I use the 1500 and leave it warm up for about an hour before I use the scale. And will ocasionally check it agains a balance beam scale to insure I am getting the right readings. (not very often do I check it)

As the electronic scales warm up, the little sensor that weighs the loads, will change so it is a good idea to every now and then (one hour) reset the zero. This is normal for an electronic scale that uses 110 volts.

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Last edited by Jim243; June 26, 2011 at 09:30 AM.
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Old June 26, 2011, 09:16 AM   #4
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I will try the warm up drill, that does make sense. I dont use the battery, I always use the transformer from 110V. I do periodically recheck with the calibration weights, this whole drifting thing was making me nervous!!
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Old June 26, 2011, 09:39 AM   #5
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After a good long warm up period, if the scale is still losing zero too fast, you should try using a fresh battery instead of the transformer. If that doesn't work then the scale needs service.

I have a voltmeter here on my desk (on a UPS box), and during the summer months it's not unusual to see the line voltage vary from 109 to 122 VAC (it's 116 VAC right now), and sometimes it shifts very fast, not a slow drift up or down. That may be what's happening in your case. Generally, electronics have good voltage regulation circuits, but a scale is so sensitive that it may not be able to keep up.
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Old June 26, 2011, 10:26 AM   #6
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Now THAT I hadn't thought of all these years.


(I've generally tracked the weight registered when I remove the pan to dump the powder. If/when that wanders (>0.1), I reset zero and press on.)

Surprisingly, I've found that a slightly different empty-pan zero doesn't appreciably effect the final powder net weight... since the machine recal's on that new zero and the added powder weight is measured relative to that zero.

I'll now go plug a VOM into the wall socket and watch the summer rollercoaster.

Last edited by mehavey; June 26, 2011 at 11:54 AM.
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Old June 26, 2011, 11:10 AM   #7
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I'm pretty sure modern scales are sophisticated enough to deal with voltage fluctuations but can't rule out some effects. I couldn't get my PACT to settle down enough to calibrate for a spur-of-the-moment loading session this morning so I fired up the RCBS Chargemaster and it settled right in and did the job. These digital scales are more sensitive than most folks realize. I guess being a little temperamental comes with the territory. Some days we have to drag out the old balance beam.
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Old June 26, 2011, 11:46 AM   #8
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What did RCBS say?
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Old June 26, 2011, 11:52 AM   #9
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Thanks for all you input everyone, hadnt thought about voltage fluctuations.
I have not yet contacted RCBS, I think I may shoot them an email and see if they answer with any thoughts.
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Old June 26, 2011, 04:41 PM   #10
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RCBS Rangemaster 750

I have had one for years and as the rest of the guys have said: Warmup!
Also be carefull of air vents in the celling, or a desk fan. When air condition or heating is circulating in you reloading room, just the sliightest of air blowing on top of the, or into the pan will give you a false reading.

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Old June 26, 2011, 04:57 PM   #11
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It often takes a lot of time and tweaking to use one of those "fast" digital powder scales.

My 45 year old beam scale settles in a couple-three seconds, no batteries or line power, no warm-up is needed - it's always ready to use, neither zero or calibration ever drifts and it's still as dead-on accurate as when it was new. But, I'm a fading dynasoar who doesn't always appreciate the LCD wonders of modern technology so what do I know?
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Old June 26, 2011, 05:06 PM   #12
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I have read that florescent lights can screw with them to. When I reload even with my ceiling fan on low will play with my RCBS charge master scale a little. I looked at my instructions for my RCBS Charge Master Scale and they recommend running it off a UPS.
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Old June 26, 2011, 07:48 PM   #13
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rottieman33, where in your manual does it say that? My Chargemaster 1500 is less than a year old and the manual doesn't mention UPS. Neither does the online manual.

FWIW, I have a fluorescent lamp about 3 feet from my scale and it has no effect on the readings.
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Old June 27, 2011, 01:53 PM   #14
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I looked at my instructions for my RCBS Charge Master Scale and they recommend running it off a UPS.
This is not, in and of itself, good advice. I must assume that given the course of the thread, that power conditioning is what is being sought in the suggestion of a UPS. One must understand, however, the differences between UPS's.

There are the standby types, and online types. Most of your "Best Buy" bargain UPS's are the standby type. This means that when they sense power loss, they kick their output to battery supplied power in some amount of time (typically 6 milliseconds). They do nothing during normal operation to condition the power being delivered to the load.

The online type feeds conditioned power to the load at all times, thereby controlling the quality of said power at all times. These are not as easy to find, and are more expensive.

It would be substantially more cost effective to just run the unit using batteries.

As for my Rangemaster 750, I just leave it on 24/7. Never had a problem yet.
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Old June 28, 2011, 12:44 AM   #15
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I actually ran my 1500 on a Trippi power conditioner for a while. It made absolutely no difference at all. It still drifted similar to mehavey's, +0.1gn IF I left the charge on the scale too long, with or without the power conditioner. But, new "fresh" readings are always spot on when compared to a balance scale.
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Old June 28, 2011, 05:09 PM   #16
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could have been caused by bad light bulbs, we were burning bulbs out too often, I called the power company and informed them my voltage was +124 volts, they came out and check, sure enough it was 124 on both legs and that was good and informed me I should stop watching the meter. Nice to have but not not necessary, I have a series plug that reads volts, amps and watts then computes the cost when cost of electricity is known (per hour).

I do not know the age of my digital RCBS scales, the scale has been updated to interface with a HP printer, anyhow, the instructions says the drift of the scales can be caused by the rise and fall of the voltage to the panel, the instructions indicate the scales adjust itself automatically when the voltage changes.

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