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Old March 14, 2009, 01:22 PM   #1
landcruzr
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Join Date: February 16, 2009
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lyman dps3 scale wont hold zero?!

So I bought a Lyman DPS3 and followed all the instructions-over and over again- and I still cant get the thing to hold a zero for more than one powder drop- then it "wanders" off zero- and I recalibrate, dump one charge, and it wanders off again-
I have even gone as far as to place the thing on the concrete floor to ensure a solid surface free of movement and it still wanders-
Any help would be appreciated!!!!
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Old March 14, 2009, 02:30 PM   #2
kraigwy
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I got one of those that does the same thing. I would trust it to measure feed for my horses.
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Old March 14, 2009, 02:54 PM   #3
Unclenick
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I don't have that model, but, in general, less expensive scales have plastic load cells that are more prone to hysteresis than metal ones. Some behave well and some don't. Worst case, you should return it with a complaint and ask them to send you a replacement that their technician has checked to be sure it works well.

That said, a couple of other steps may help. One is to let the thing warm up a day. The strain gauges in load cells are foil resistors that change value as they stretch. They dissipate some heat as current flows through them and giving the heat time to permeate the gauge, the glue holding it to the load cell and the cell itself will limit drift. Most lab scales keep the load cell powered up 24/7 any time they are plugged in, whether the rest of the scale is on or not.

Do your check weight calibration only after that warm up period.

Your concrete floor is actually good not only from the the standpoint of vibration, but also in that it changes temperature slowly. If you want to use a bench, you can improve on it by getting a piece of hard wood the right size to serve as a base for the scale and setting a mouse pad between it and the bench. Next, turn a cardboard box upside down over it so that the air doesn't try to change its temperature much during the warm-up period. Remove it only for using the machine.

I believe that unit has an integral draft shield? If you have to use it with the draft shield flipped up it will register everything from your breath to, in some cases, static electric charge on your hands. If you need to operate it with the draft shield up and you don't have a truly draft-free environment, then try setting it into a cardboard box that is on its side so the box top is sideways and open to you.

If you have static electricity in your environment (any place with low humidity can) then go to Radio Shack and get an anti-static wrist band to wear that you ground to a water pipe or other earth ground. That's not a bad practice when handling gunpowder and primers in dry air anyway.

If you've already done the above, then send it back. I'd send it to the factory rather than return it to a vendor. You want someone in a position to pick a working one out for you.
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Old March 14, 2009, 03:09 PM   #4
billcarey
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That ain't no bottom dweller scale (if you compare to those costing $25) but is a good example of why electronic scales have to be watched closely. I worked 24 yrs in a semiconductor mfg facility and there is NO way I'd trust a $300 electronic scale to keep a hand cannon from blowing up in my face. It can glitch big time without warning.
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